ABCMdb

ABCC7 p.Gly970Arg

ClinVar:	c.2908G>C , p.Gly970Arg D , Pathogenic c.2908G>A , p.Gly970Ser ? , not provided c.2909G>A , p.Gly970Asp D , Likely pathogenic
CF databases:	c.2908G>C , p.Gly970Arg D , CF-causing ; CFTR1: The G970R mutation (G->C at nucleotide position 3040) in exon 15 was found in 1 out of 34 unrelated Belgian CF chromosomes (7 [delta]F508 and 27 non-[delta]F508 CF chromosomes). c.2908G>A , p.Gly970Ser (CFTR1) ? , This mutation was detected by DHPLC analysis followed by direct sequencing. This mutation was found in one CF patient of Egyptian origin who carried the F508 del on the second CF allele c.2909G>A , p.Gly970Asp (CFTR1) ? , The above mutation was found by SSCP/HA in a compound heterozygote; the other mutation is an 8 nt deletion in exon 4. Further patient information will be reported. <BR> (Corrected August 4, 1997)
Predicted by SNAP2:	A: D (80%), C: D (85%), D: D (91%), E: D (95%), F: D (95%), H: D (95%), I: D (91%), K: D (95%), L: D (95%), M: D (91%), N: D (85%), P: D (95%), Q: D (91%), R: D (95%), S: D (80%), T: D (91%), V: D (91%), W: D (95%), Y: D (95%),
Predicted by PROVEAN:	A: D, C: D, D: D, E: D, F: D, H: D, I: D, K: D, L: D, M: D, N: D, P: D, Q: D, R: D, S: D, T: D, V: D, W: D, Y: D,

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[hide] Two novel mutations in a cystic fibrosis patient o... Hum Genet. 1999 Jun;104(6):511-5. Wagner JA, Vassilakis A, Yee K, Li M, Hurlock G, Krouse ME, Moss RB, Wine JJ
Two novel mutations in a cystic fibrosis patient of Chinese origin.
Hum Genet. 1999 Jun;104(6):511-5., [PMID:10453741]

Abstract [show]
Cystic fibrosis is rare in non-Caucasian populations, and in such populations little is known about the spectrum of mutations and polymorphisms in the CFTR gene. We studied a 23-year-old patient of Chinese ethnicity with sweat chloride values of 104 mM/l, pancreatic sufficiency, an FEV1 60% of normal, sputum cultures positive for Staphylococcus aureus and Burkholderia cepacia, and a history of allergic bronchopulmonary aspergillosis. Genetic screening for 31 common CFTR mutations was negative, leading us to search for unknown mutations using single-strand conformation polymorphism and heteroduplex analysis (SSCP/HA). Two novel mutations were detected. In exon 4, a deletion of 8 bp (451458, deltaGCTTCCTA) causes a frameshift and immediately creates a stop codon. In exon 16, mutation 3041G-->A causes the missense change G970D. Functional analysis using an isotopic flux assay indicated that the G970D mutation retains partial function; western blotting indicated that the protein is glycosylated. The patient is heterozygous for the common polymorphisms (2694T/G) in exon 14a and (GATT)6/7 in intron 6a, indicating that these variants arose in ancestors common to Caucasians and Chinese.

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63 G970D is a novel mutation, but G970R was reported previously in a single Belgian patient (Cuppens et al. 1993). Login to comment
96 Mutation G970D affects the same codon as the previously reported G970R (Cuppens et al. 1993). Login to comment
98 Seibert et al. (1996) examined all three point mutations in the third cytoplasmic loop and determined that S945L and H949Y are trafficking mutations, while G970R is trafficked normally, but shows significantly reduced function when tested with an iodide efflux assay. Login to comment
99 Single channel recordings indicated that the open probability of G970R was reduced as a result of a significantly reduced mean burst duration. Login to comment
100 To help shed light on the structural basis for reduced function of G970R, Seibert et al. (1996) mutated the glycine at position 970 to arginine, alanine, methionine, glutamic acid or lysine. Login to comment

[hide] Aberrant CFTR-dependent HCO3- transport in mutatio... Nature. 2001 Mar 1;410(6824):94-7. Choi JY, Muallem D, Kiselyov K, Lee MG, Thomas PJ, Muallem S
Aberrant CFTR-dependent HCO3- transport in mutations associated with cystic fibrosis.
Nature. 2001 Mar 1;410(6824):94-7., 2001-03-01 [PMID:11242048]

Abstract [show]
Cystic fibrosis (CF) is a disease caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR). Initially, Cl- conductance in the sweat duct was discovered to be impaired in CF, a finding that has been extended to all CFTR-expressing cells. Subsequent cloning of the gene showed that CFTR functions as a cyclic-AMP-regulated Cl- channel; and some CF-causing mutations inhibit CFTR Cl- channel activity. The identification of additional CF-causing mutants with normal Cl- channel activity indicates, however, that other CFTR-dependent processes contribute to the disease. Indeed, CFTR regulates other transporters, including Cl(-)-coupled HCO3- transport. Alkaline fluids are secreted by normal tissues, whereas acidic fluids are secreted by mutant CFTR-expressing tissues, indicating the importance of this activity. HCO3- and pH affect mucin viscosity and bacterial binding. We have examined Cl(-)-coupled HCO3- transport by CFTR mutants that retain substantial or normal Cl- channel activity. Here we show that mutants reported to be associated with CF with pancreatic insufficiency do not support HCO3- transport, and those associated with pancreatic sufficiency show reduced HCO3- transport. Our findings demonstrate the importance of HCO3- transport in the function of secretory epithelia and in CF.

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186 letters to nature 96 NATURE |VOL 410 |1 MARCH 2001 |www.nature.com HCO3 -/Cl- transportratio 0 0.25 0.50 0.75 1.00 WT I148T G178R R297Q G551D H620Q G970R A1067T G1244E S1255P G1349D E193K G551S A800G H949Y R1070Q Pancreatic insufficient Pancreatic sufficientD648V N CI148T G178R E193K R297Q R117H A1067T R1070Q G1244E S1255P G1349D NBD2 RD H949Y G970R CL4CL3CL2CL1 NBD1 G551D G551S H620Q D648V A800G Figure 3 The HCO3:Cl-transport ratio of CFTR mutants associated with CF. Login to comment
212 Acknowledgements We thank H. Cuppens from the European CF Consortium for informing us that the G970R mutation results in pancreatic insuf®ciency. Login to comment

[hide] Cystic fibrosis: a worldwide analysis of CFTR muta... Hum Mutat. 2002 Jun;19(6):575-606. Bobadilla JL, Macek M Jr, Fine JP, Farrell PM
Cystic fibrosis: a worldwide analysis of CFTR mutations--correlation with incidence data and application to screening.
Hum Mutat. 2002 Jun;19(6):575-606., [PMID:12007216]

Abstract [show]
Although there have been numerous reports from around the world of mutations in the gene of chromosome 7 known as CFTR (cystic fibrosis transmembrane conductance regulator), little attention has been given to integrating these mutant alleles into a global understanding of the population molecular genetics associated with cystic fibrosis (CF). We determined the distribution of CFTR mutations in as many regions throughout the world as possible in an effort designed to: 1) increase our understanding of ancestry-genotype relationships, 2) compare mutational arrays with disease incidence, and 3) gain insight for decisions regarding screening program enhancement through CFTR multi-mutational analyses. Information on all mutations that have been published since the identification and cloning of the CFTR gene's most common allele, DeltaF508 (or F508del), was reviewed and integrated into a centralized database. The data were then sorted and regional CFTR arrays were determined using mutations that appeared in a given region with a frequency of 0.5% or greater. Final analyses were based on 72,431 CF chromosomes, using data compiled from over 100 original papers, and over 80 regions from around the world, including all nations where CF has been studied using analytical molecular genetics. Initial results confirmed wide mutational heterogeneity throughout the world; however, characterization of the most common mutations across most populations was possible. We also examined CF incidence, DeltaF508 frequency, and regional mutational heterogeneity in a subset of populations. Data for these analyses were filtered for reliability and methodological strength before being incorporated into the final analysis. Statistical assessment of these variables revealed that there is a significant positive correlation between DeltaF508 frequency and the CF incidence levels of regional populations. Regional analyses were also performed to search for trends in the distribution of CFTR mutations across migrant and related populations; this led to clarification of ancestry-genotype patterns that can be used to design CFTR multi-mutation panels for CF screening programs. From comprehensive assessment of these data, we offer recommendations that multiple CFTR alleles should eventually be included to increase the sensitivity of newborn screening programs employing two-tier testing with trypsinogen and DNA analysis.

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109 Mutational Arrays, Detection Rates and Methods by Region* Estimated Projected detection of Number of Number of Country/ allele two CFTR mutations chromosomes Region Mutation array detectiona mutationsb includedc (max/min)d Reference Europe Albania ∆F508 (72.4%) C276X (0.7%) 74.5 55.5 4 270/146 CFGAC [1994]; Macek et al. G85E (0.7%) R1070Q (0.7%) [2002] Austria ∆F508 (62.9%) 457TAT→G (1.2%) 76.6 58.7 11 1516/580 Estiville et al. [1997]; Dörk et al. (total) G542X (3.3%) 2183AA→G (0.7%) [2000]; Macek et al. [2002] CFTRdele2,3 (2.1%) N1303K (0.6%) R1162X (1.9%) I148T (0.5%) R553X (1.7%) R117H (0.5%) G551D (1.2%) Austria ∆F508 (74.6%) 2183AA→G (2.4%) 95.3 90.8 8 126 Stuhrmann et al. [1997] (tyrol) R1162X (8.7%) G551D (1.6%) G542X (2.4%) R347P (1.6%) 2789+5G→A (2.4%) Q39X (1.6%) Belarus ∆F508 (61.2%) R553X (0.5%) 75.2 56.6 9 278/188 Dörk et al. [2000]; Macek et al. G542X (4.5%) R334W (0.5%) [2002] CFTRdele2,3 (3.3%) R347P (0.5%) N1303K (3.2%) S549N (0.5%) W1282X (1.0%) Belgium ∆F508 (75.1%) 622-1A→C (0.5%) 100.0 100.0 27 1504/522 Cuppens et al. [1993]; Mercier et G542X (3.5%) G458V (0.5%) al. [1993]; CFGAC [1994]; N1303K (2.7%) 1898+G→C (0.5%) Estivill et al.[1997] R553X (1.7%) G970R (0.5%) 1717-1G→A (1.6%) 4218insT (0.5%) E60X (1.6%) 394delTT (0.5%) W1282X (1.4%) K830X (0.5%) 2183A→G+2184delA (1.2%) E822K (0.5%) W401X (1.0%) 3272-1G→A (0.5%) A455E (1.0%) S1161R (0.5%) 3272-26A→G (1.0%) R1162X (0.5%) S1251N (1.0%) 3750delAG (0.5%) S1235R (0.8%) S1255P (0.5%) ∆I507 (0.6%) Bulgaria ∆F508 (63.6%) R75Q (1.0%) 93.0 86.5 21 948/432 Angelicheva et al. [1997]; (total) N1303K (5.6%) 2183AA→G (0.9%) Estivill et al. [1997]; Macek G542X (3.9%) G1244V+S912L (0.9%) et al. [2002] R347P (2.2%) G85E (0.9%) 1677delTA (2.1%) 2184insA (0.9%) R1070Q (1.8%) L88X+G1069R (0.8%) Q220X (1.2%) 2789+5G→A (0.8%) 3849+10KbC→T (1.1%) G1244E (0.8%) W1282X (1.0%) 1717-1G→A (0.8%) 2176insC (1.0%) Y919C (0.7%) G1069R (1.0%) WORLDWIDEANALYSISOFCFTRMUTATIONS581 Bulgaria 1) DF508 4) 1677delTA - - 6 13 Angelicheva et al. [1997] (ethnic 2) R347P 5) Q493R Turks) 3) G542X 6) L571S - - 1 30 Angelicheva et al. [1997] Bulgaria 1) DF508 (100.0%) (Gypsy) Croatia ∆F508 (64.5%) G551D (1.1%) 72.5 52.6 5 276 Macek et al. [2002] G542X (3.3%) 3849+10KbC→T (0.7%) N1303K (2.9%) Czech ∆F508 (70.0%) 1898+1G→T (2.0%) 89.6 80.3 10 2196/628 CFGAC [1994]; Estiville et al. Republic CFTRdele2,3 (5.5%) 2143delT (1.2%) [1997]; Dörk et al. [2000]; G551D (3.8%) R347P (0.8%) Macek et al. [2002] N1303K (2.9%) 3849+10KbC→T (0.6%) G542X (2.2%) W1282X (0.6%) Denmark ∆F508 (87.5%) G542X (0.7%) 92.3 85.2 6 1888/678 CFGAC [1994]; Schwartz et al. (excluding 394delTT (1.8%) 621+1G→T (0.6%) [1994]; Estiville et al. [1997] Faroe) N1303K (1.1%) 3659delC (0.6%) Estonia ∆F508 (51.7%) R117C (1.7%) 80.2 64.3 10 165/80 Estivill et al. [1997]; Klaassen et 394delTT (13.3%) E217G (1.7%) al. [1998]; Macek et al. S1235R (3.3%) R1066H (1.7%) [2002] 359insT (1.7%) 3659delC (1.7%) I1005R (1.7%) S1169X (1.7%) Finland ∆F508 (46.2%) G542X (1.9%) 78.8 62.1 4 132/52 CFGAC [1994]; Kere et al. 394delTT (28.8%) 3372delA (1.9%) [1994]; Estivill et al. [1997] France ∆F508 (67.7%) 2789+5G→T (0.79%) 79.7 63.6 12 17854/7420 Chevalier-Porst et al. [1994]; (total) G542X (2.94%) 2184delA+2183A→G (0.77%) Estivill et al. [1997]; Claustres et al. [2000]; Guilloud-Bataille N1303K (1.83%) G551D (0.74%) et al. [2000] 1717-1G→A (1.35%) 1078delT (0.63%) W1282X (0.91%) ∆I507 (0.62%) R553X (0.86%) Y122K (0.59%) France ∆F508 (75.8%) R297Q (0.8%) 98.7 97.4 18 599/365 Férec et al. [1992]; Scotet et al. (Brittany) 1078delT (4.0%) R347H (0.8%) [2000] G551D (3.6%) I1234V (0.8%) N1303K (3.0%) R553X (0.8%) R117H (1.7%) 2789+5G→A (0.8%) 3272-26A→G (1.3%) 4005+1G→A (0.7%) G542X (1.1%) 621+1G→T (0.6%) 1717-1G→A (1.0%) ∆I507 (0.6%) G1249R (0.8%) W846X (0.5%) France ∆F508 (70.0%) N1303K (0.8%) 90.4 81.7 16 250 Claustres et al. [1993] (southern) G542X (6.4%) 3737delA (0.8%) 1717-1G→A (1.6%) R1162X (0.8%) L206W (1.2%) Y1092X (0.8%) R334W (1.2%) S945L (0.8%) ∆I507 (1.2%) K710X (0.8%) 2184delA (1.2%) 1078delT (0.8%) R1158X (1.2%) Y122X (0.8%) (Continued) BOBADILLAETAL. Login to comment

[hide] Comparison of the CFTR mutation spectrum in three ... Hum Mutat. 2003 Jul;22(1):105. Scotet V, Barton DE, Watson JB, Audrezet MP, McDevitt T, McQuaid S, Shortt C, De Braekeleer M, Ferec C, Le Marechal C
Comparison of the CFTR mutation spectrum in three cohorts of patients of Celtic origin from Brittany (France) and Ireland.
Hum Mutat. 2003 Jul;22(1):105., [PMID:12815607]

Abstract [show]
This study aims to compare the spectrum of the mutations identified in the gene responsible for cystic fibrosis in three cohorts of patients of Celtic origin from Brittany and Ireland. It included 389 patients from Brittany, 631 from Dublin and 139 from Cork. The CFTR gene analysis relied on the detection of the most common mutations, followed by a complete gene scanning using DGGE or D-HPLC. High mutation detection rates were obtained in each cohort: 99.6%, 96.8%, and 96.0% respectively. A high frequency of the c.1652_1655 del3 mutation (F508del: 74.8% to 81.3%) and of the "Celtic" mutation (c.1784G>A (G551D): 3.7% to 9.7%) was observed in each population. Apart from this, the mutation spectrums differed. In Brittany, the most common abnormalities were: c.1078delT (3.6%), c.4041C>G (N1303K: 1.4%), c.2670G>A (W846X(2): 1.0%) and c.1717-1G>A (1.0%), whereas in the cohort of Dublin, the main mutations were: c.482G>A (R117H: 3.0%), c.1811G>C (R560T: 2.4%) and c.621+1G>T (1.7%). Finally, in the Cork area, only the c.482G>A mutation (R117H) reached a frequency of 1%. Two previously-unreported mutations were identified in the Dublin cohort: c.2623-2A>G and c.3446T>G (M1105R). This collaborative study highlights the similarities of the CFTR alleles in the Breton and Irish populations, but also the disparities that exist between these populations, despite their common origin. Each population has its own history, with its mixture of founder effects and genetic drifts, which are at the origin of the current mutation distribution. The molecular study of the CFTR gene provides new tools for retracing European populations' histories.

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64 Spectrum of the CFTR Mutations Identified in the Cohorts from Brittany, Dublin Centre, and Cork Area Nucleotide Amino acid change * change Exon Number Frequency Number Frequency Number Frequency 211delG 2 1 0.1% 310G>T E60X 3 5 0.6% 4 0.3% 347C>A A72D 3 1 0.1% 368G>A W79X 3 1 0.1% 386G>A G85E 3 2 0.3% 3 0.2% 403G>A G91R 3 2 0.3% 482G>A R117H 4 4 0.5% 38 3.0% 4 1.4% 498T>A Y122X 4 1 0.1% 574delA 4 1 0.1% 577G>A G149R 4 1 0.1% 621+1G>T int 4 5 0.6% 21 1.7% 790C>T Q220X 6a 1 0.1% 875+1G>C int 6a 1 0.4% 905delG 6b 1 0.1% 1065C>G F311L 7 2 0.3% 1078delT 7 28 3.6% 1132C>T R334W 7 1 0.1% 1172G>A R347H 7 5 0.6% 1172G>T R347L 7 1 0.1% 1172G>C R347P 7 1 0.1% 1187G>A R352Q 7 3 0.2% 2 0.7% 1208A>G Q359R 7 1 0.1% 1154insTC 7 2 0.2% 1221delCT 7 2 0.3% 1248+1G>A int 7 1 0.1% 1249-27delTA int 7 1 0.4% 1334G>A W401X 8 1 0.1% 1461ins4 9 5 0.4% 1471delA 9 2 0.2% 1607C>T S492F 10 2 0.3% 1609C>T Q493X 10 1 0.1% 1648_1653delATC I507del 10 3 0.4% 10 0.8% 1 0.4% 1652_1655del 3 bp F508del 10 582 74.8% 966 76.5% 226 81.3% 1690G>T V520F 10 4 0.3% 1717-1G>A int 10 8 1.0% 9 0.7% 1756G>T G542X 11 5 0.6% 8 0.6% 1779T>G S549R 11 1 0.1% 1784G>A G551D 11 29 3.7% 82 6.5% 27 9.7% 1789C>G R553G 11 1 0.1% 1789C>T R553X 11 3 0.4% 1 0.1% 1806delA 11 1 0.1% 1811G>A R560K 11 2 0.3% 1811G>C R560T 11 30 2.4% 2 0.7% 1819T>A Y563N 12 1 0.1% 1853C>A P574H 12 1 0.1% 1898+1G>A int 12 1 0.1% 2184delA 13 1 0.1% 1 0.1% 2184insA 13 1 0.1% 2622+1G>A int 13 1 0.1% 2 0.2% 2622+1G>T int 13 1 0.1% 2623-2A>G ** int 13 1 0.1% 2670G>A W846X2 14a 8 1.0% 2752-1G>T int 14a 1 0.1% 2752-26A>G int 14a 2 0.2% 2789+5G>A int 14b 6 0.8% 2966C>T S945L 15 2 0.3% 3007delG 15 4 0.3% 3040G>C G970R 15 1 0.1% 3062C>T S977F 16 1 0.1% 3120+1G>A int 16 1 0.1% 3272-26A>G int 17a 4 0.5% 2 0.2% 2 0.7% 3320dupli(CTATG) 17b 1 0.1% 3329G>A R1066H 17b 1 0.1% 3340C>T R1070W 17b 1 0.1% 3408C>A Y1092X 17b 7 0.9% 3442G>T E1104X 17b 1 0.1% 3446T>G ** M1105R 17b 1 0.1% 3586G>C D1152H 18 1 0.1% 3601-17T>C + 1367delC int 18 + 9 1 0.1% 3616C>T R1162X 19 1 0.1% 2 0.2% 3659delC 19 2 0.2% 3832A>G I1234V 19 2 0.3% 3849+4A>G int 19 1 0.1% 3849+10kbC>T int 19 3 0.2% 3877G>A G1249R 20 1 0.1% 3884G>A S1251N 20 1 0.1% 3898insC 20 1 0.1% 3905insT 20 2 0.3% 3978G>A W1282X 20 3 0.4% 4005+1G>A int 20 6 0.8% 4016insT 21 1 0.1% 4041C>G N1303K 21 11 1.4% 5 0.4% 4136T>C L1335P 22 1 0.1% 1 0.4% 4279insA 23 1 0.1% Unidentified Unidentified - 3 0.4% 41 3.2% 11 4.0% Total 778 100.0% 1262 100.0% 278 100.0% * All nucleotide changes correspond to cDNA numbering. Login to comment

[hide] The CFTR 3849+10kbC->T and 2789+5G->A alleles are ... Eur Respir J. 2005 Mar;25(3):468-73. Dugueperoux I, De Braekeleer M
The CFTR 3849+10kbC->T and 2789+5G->A alleles are associated with a mild CF phenotype.
Eur Respir J. 2005 Mar;25(3):468-73., [PMID:15738290]

Abstract [show]
Most cystic fibrosis (CF) transmembrane receptor mutations are rare. The French CF Registry offers an opportunity to study the genotype-phenotype relationship of these rare alleles. Since 1992, 39 CF patients carrying one copy of the 3849+10kbC->T mutation and 88 the 2789+5G->A allele have been seen at least once in a CF care centre. Among them, 16 carrying the 3849+10kbC->T/Delta F508 genotype and 34 with the 2789+5G->A/Delta F508 genotype were seen in 2000. Their age at diagnosis, sweat chloride concentration, anthropometric and lung function results, and clinical aspects were compared with those homozygous for the Delta F508 mutation matched for sex, age and CF care centre. Major differences, most of them statistically significant, in the age at diagnosis, prevalence of pancreatic insufficiency, and other clinical signs, anthropometric and lung function measures were observed between both compound heterozygote groups and their matched Delta F508/Delta F508 groups. The mean sweat chloride concentration was also lower (close to normal values) among 3849+10kbC->T/Delta F508 patients, but not among 2789+5G->A/Delta F508 patients. In conclusion, both mutations studied here are associated with a milder course of cystic fibrosis disease. The 3849+10kbC->T and 2789+5G->A alleles are splice site mutations, leading to abnormal mRNA; however, a small amount of normally spliced transcripts can also be detected. The presence of these small amounts of normal cystic fibrosis transmembrane receptor protein in these cystic fibrosis patients is likely to be responsible for the milder severity of disease and a better life expectancy.

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63 Although only borderline significant, lung function was definitely better in the 3849+10kbC-.T/DF508 group (FEV1 83.0% and FVC 91.6% pred) than in the DF508 homozygote group (FEV1 59.9% TABLE 1 Genotypes identified among cystic fibrosis patients sharing the 3849+10kbC-.T or the 2789+5G-.A mutation Genotypes 3849+10kbC-.T 2789+5G-.A DI507 2 DF508 27 61 1525-1G-.A 1 1717-1G.A 1 2183AA.G 3 3129del4 1 3659delC 1 G542X 4 6 G551D 1 G970R 2 G1244E 2 L558S 1 M1V 1 N1303K 1 R347P 1 R553X 1 1 R1066C 1 S1251N 1 Unknown 1 6 Total 39 88 I. DUGUE´PE´ROUX AND M. DE BRAEKELEER MILD PHENOTYPE ASSOCIATED WITH TWO CFTR MUTATIONS c and FVC 76.9% pred). Login to comment

[hide] Serum zinc concentrations in cystic fibrosis patie... Biol Trace Elem Res. 2007 Oct;119(1):19-26. Van Biervliet S, Van Biervliet JP, Vande Velde S, Robberecht E
Serum zinc concentrations in cystic fibrosis patients aged above 4 years: a cross-sectional evaluation.
Biol Trace Elem Res. 2007 Oct;119(1):19-26., [PMID:17914215]

Abstract [show]
AIM: Assess the risk of zinc (Zn) deficiency in the older cystic fibrosis (CF) population. METHOD: Cross-sectional investigation of all CF patients above the age of 4 followed at the Ghent University center between 2002 and 2003. Data on age, weight, height z-score, pancreatic and pulmonary functions, chronic Pseudomonas infection, and CF transmembrane conductance regulator (CFTR) mutations were collected. Serum Zn, vitamins (vit) A and E, retinol-binding protein (RBP), albumin, sedimentation rate, total IgG, and cholesterol were determined. Serum Zn was compared with a local healthy control group (Van Biervliet et al., Biol Trace Elem Res 94:33-40, 2003) and with literature data (Hotz C, et al. Am J Clin Nutr 78:756-764, 2003). RESULTS: 101 patients (median age 16 years) were included. There was no difference in serum Zn concentration between CF patients and controls. In CF patients no difference in serum Zn concentration between pancreatic-sufficient or pancreatic-insufficient patients was seen. Serum Zn was not associated to nutritional status or height z-score. A significant association serum Zn to serum albumin (p < 0.0005) and to vit A (p < 0.01) was seen. No associations of serum Zn to serum vit E, RBP, cholesterol, or CFTR were present, but there is a significant association serum Zn to forced vital capacity (p < 0.01). Serum Zn was not associated to inflammatory parameters or chronic Pseudomonas infection. CONCLUSION: Comparison of CF patients with local controls revealed no significant differences. However, because persisting steatorrhea increases Zn loss (Easley et al., J Pediatr Gastroenterol Nutr 26:136-139, 1998) and 12.6% of our population has a serum Zn below the p value of 2.5 of the NHANES II study (Hotz C, et al. Am J Clin Nutr 78:756-764, 2003), there could remain an increased risk of Zn deficiency in some CF patients. Furthermore, the association with pulmonary function needs more investigation.

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73 Table 1 Genotype of the 101 CF Patients: Details of the CF Mutations and Classification into Two Groups Genotype Groups Genotype No of Patients A ΔF508/ΔF508 47 ΔF508/E60X 1 ΔF508/G542X 7 ΔF508/N1303K 3 ΔF508/Q493X 1 ΔF508/1717-1G→A 1 ΔF508/Y1092X 1 ΔF508/394delTT 1 ΔF508/R785X 1 ΔF508/R553X 1 ΔF508/ΔI507 1 394delTT/394delTT 1 N1303K/N1303K 2 B ΔF508/3849+10kbC-T 1 ΔF508/306ΔTAGA 1 ΔF508/S1251N 8 ΔF508/L927P 1 G458V/1717-1G→A 1 ΔF508/I336K 2 G542X/622-2 A→C 1 ΔF508/G970R 3 ΔF508/3272-26A→G 2 ΔF508/R117H 2 ΔF508/2789+5G→A 2 1717-1G->A/S1251N 1 G542X/G970R 1 394delTT/Y913C 1 N1303K/deletion exon 19 1 Unidentified/unidentified 2 3600+2insTA/2005 del T 1 ΔF508/1898+1G→A 1 Deletion exon 2/del exon 2 1 There was no difference according to gender or age. Login to comment

[hide] Atomic model of human cystic fibrosis transmembran... Cell Mol Life Sci. 2008 Aug;65(16):2594-612. Mornon JP, Lehn P, Callebaut I
Atomic model of human cystic fibrosis transmembrane conductance regulator: membrane-spanning domains and coupling interfaces.
Cell Mol Life Sci. 2008 Aug;65(16):2594-612., [PMID:18597042]

Abstract [show]
We describe herein an atomic model of the outward-facing three-dimensional structure of the membrane-spanning domains (MSDs) and nucleotide-binding domains (NBDs) of human cystic fibrosis transmembrane conductance regulator (CFTR), based on the experimental structure of the bacterial transporter Sav1866. This model, which is in agreement with previous experimental data, highlights the role of some residues located in the transmembrane passages and directly involved in substrate translocation and of some residues within the intracellular loops (ICL1-ICL4) making MSD/NBD contacts. In particular, our model reveals that D173 ICL1 and N965 ICL3 likely interact with the bound nucleotide and that an intricate H-bond network (involving especially the ICL4 R1070 and the main chain of NBD1 F508) may stabilize the interface between MSD2 and the NBD1F508 region. These observations allow new insights into the ATP-binding sites asymmetry and into the molecular consequences of the F508 deletion, which is the most common cystic fibrosis mutation.

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250 G178R (involving ICL1) and G970R (involving ICL3) are two CF-causing mutations. Login to comment
251 The G178R mutant exhibits impaired anion translocation capacity [73] and the G970R mutant is probably involved in obtaining or maintaining the open state of the transporter [74]. Login to comment
255 Other CF-associated mutations of interest in ICL1 and ICL3 are (i) E193K, a mutation of an ICL1 residue that exhibits, similarly to G178R, impaired anion translocation capacity [73], and (ii) S945L, H949Yand G970R, which affect ICL3 residues and are probably involved (as G970R) in obtaining or maintaining the open state of the transporter [74]. Login to comment

[hide] Mutation-specific potency and efficacy of cystic f... J Pharmacol Exp Ther. 2009 Sep;330(3):783-91. Epub 2009 Jun 2. Caputo A, Hinzpeter A, Caci E, Pedemonte N, Arous N, Di Duca M, Zegarra-Moran O, Fanen P, Galietta LJ
Mutation-specific potency and efficacy of cystic fibrosis transmembrane conductance regulator chloride channel potentiators.
J Pharmacol Exp Ther. 2009 Sep;330(3):783-91. Epub 2009 Jun 2., [PMID:19491324]

Abstract [show]
Cystic fibrosis (CF) is caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) Cl(-) channel. The mutations G551D and G1349D, which affect the nucleotide-binding domains (NBDs) of CFTR protein, reduce channel activity. This defect can be corrected pharmacologically by small molecules called potentiators. CF mutations residing in the intracellular loops (ICLs), connecting the transmembrane segments of CFTR, may also reduce channel activity. We have investigated the extent of loss of function caused by ICL mutations and the sensitivity to pharmacological stimulation. We found that E193K and G970R (in ICL1 and ICL3, respectively) cause a severe loss of CFTR channel activity that can be rescued by the same potentiators that are effective on NBD mutations. We compared potency and efficacy of three different potentiators for E193K, G970R, and G551D. The 1,4-dihydropyridine felodipine and the phenylglycine PG-01 [2-[(2-1H-indol-3-yl-acetyl)-methylamino]-N-(4-isopropylphenyl)-2-phenylac etamide] were strongly effective on the three CFTR mutants. The efficacy of sulfonamide SF-01 [6-(ethylphenylsulfamoyl)-4-oxo-1,4-dihydroquinoline-3-carboxylic acid cycloheptylamide], another CFTR potentiator, was instead significantly lower than felodipine and PG-01 for the E193K and G970R mutations, and almost abolished for G551D. Furthermore, SF-01 modified the response of G551D and G970R to the other two potentiators, an effect that may be explained by an allosteric antagonistic effect. Our results indicate that CFTR potentiators correct the basic defect caused by CF mutations residing in different CFTR domains. However, there are differences among potentiators, with felodipine and PG-01 having a wider pharmacological activity, and SF-01 being more mutation specific. Our observations are useful in the prioritization and development of drugs targeting the CF basic defect.

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5 We found that E193K and G970R (in ICL1 and ICL3, respectively) cause a severe loss of CFTR channel activity that can be rescued by the same potentiators that are effective on NBD mutations. Login to comment
6 We compared potency and efficacy of three different potentiators for E193K, G970R, and G551D. Login to comment
8 The efficacy of sulfonamide SF-01 [6-(ethylphenylsulfamoyl)-4-oxo-1,4-dihydroquinoline-3-carboxylic acid cycloheptylamide], another CFTR potentiator, was instead significantly lower than felodipine and PG-01 for the E193K and G970R mutations, and almost abolished for G551D. Login to comment
9 Furthermore, SF-01 modified the response of G551D and G970R to the other two potentiators, an effect that may be explained by an allosteric antagonistic effect. Login to comment
91 To this respect, we considered I148T, I175V, Q179K, and E193K in ICL1 (Seibert et al., 1997) and G970R in ICL3 (Seibert et al., 1996). Login to comment
97 E193K and G970R showed the most severe defect, with more than 10-fold decreased activity relative to wild-type CFTR (Fig. 1A). Login to comment
98 D1152H was significantly more active than E193K and G970R but approximately five times less than the wild-type protein. Login to comment
116 E193K, G970R, and D1152H. Login to comment
118 However, a significant exception was represented by G970R, which was less responsive to potentiators and, in particular, to SF-01. Login to comment
127 To confirm the results obtained with the functional assay, and to determine precisely the potency and maximal effect for each potentiator, we generated stable transfectants for E193K and G970R, the two ICL mutants having the most severe deficit in cAMP response. Login to comment
144 On the contrary, SF-01 potency was not significantly different between E193K and G970R. Login to comment
151 In all experiments, CFTRinh-172 reduced the G970R current by only 79 Ϯ 2%, whereas for the other mutants and for wild-type CFTR the inhibition was greater than 95% (98 Ϯ 1% for E193K, p Ͻ 0.01). Login to comment
161 Second, its potency, although difficult to measure because of the small size of the currents, was not different from that measured for E193K and G970R (Table 1). Login to comment
164 Kd Imax nH n ␮M ␮A/cm2 E193K PG-01 0.22 Ϯ 0.03 37.4 Ϯ 3.6 1.5 Ϯ 0.2 6 SF-01 0.74 Ϯ 0.19 20.6 Ϯ 2.7 1.3 Ϯ 0.1 9 Felodipine 0.67 Ϯ 0.14 32.7 Ϯ 2.4 1.4 Ϯ 0.1 9 G970R PG-01 0.45 Ϯ 0.07** 60.2 Ϯ 8.1 1.4 Ϯ 0.2 10 SF-01 0.45 Ϯ 0.07ns 17.6 Ϯ 2.7 1.6 Ϯ 0.2 10 Felodipine 2.03 Ϯ 0.39** 75.7 Ϯ 7.4 1.2 Ϯ 0.1 9 G551D PG-01 1.94 Ϯ 0.54*† 21.5 Ϯ 4.4 1.4 Ϯ 0.2 8 SF-01 1.10 Ϯ 0.12ns 5.9 Ϯ 0.7 1.8 Ϯ 0.3 15 Felodipine 10.22 Ϯ 1.12**†† 68.4 Ϯ 5.4 2.2 Ϯ 0.4 9 ns, nonsignificant. Login to comment
168 the same potentiator in G970R. Login to comment
180 Accordingly, the poor effectiveness of SF-01 on G551D or G970R could be explained by the prevalence of inhibitory over stimulatory activities. Login to comment
189 We found that, in G970R cells, the addition of SF-01 caused a significant reduction of the currents elicited by the subsequent application of PG-01 with a shift of the dose-response relationship. Login to comment
191 The dose response of felodipine was also altered in G970R cells by the presence of SF-01 (Fig. 6B). Login to comment
205 In G551D cells, this type of experiment produced results that were in part different from those found in G970R cells. Login to comment
206 The activity of PG-01 was altered by SF-01 as in G970R; the apparent Kd was increased by more than 3-fold (from 1.94 Ϯ 0.54 to 7.42 Ϯ 2.15 ␮M, n ϭ 7-8, p Ͻ 0.05), and the maximal response was reduced by 50% (Fig. 6C). Login to comment
220 We took into consideration various mutations in ICL1, G970R in ICL3, and D1152H, which lies between the last transmembrane segment and NBD2. Login to comment
221 Our results show that E193K, G970R, and, to a lesser extent, D1152H cause a marked decrease in CFTR activity. Login to comment
229 We focused our study on E193K and G970R, the two ICL mutants having the most severe loss in CFTR activity, and, for comparison, on G551D. Login to comment
247 The second hypothesis is that SF-01, PG-01, and felodipine have a unique binding site as potentiators but the efficacy of SF-01 is reduced relative to the other two potentiators, in particular, for G970R and G551D mutants. Login to comment
252 We found that the presence of SF-01 caused an alteration in the dose-response relationships for PG-01 and felodipine in G970R, and for PG-01 alone in G551D. Login to comment
262 This seems supported by the fact that the Kd for PG-01 and felodipine is increased by the same extent in G970R (ϳ2-fold) and in G551D (ϳ10-fold) with respect to E193K, whereas the apparent potency of SF-01 does not change. Login to comment
264 Another interesting observation regarding the G970R mutant is the noncomplete inhibition produced by CFTRinh-172. Login to comment
266 It is possible that the G970R mutation alters the CFTR activity so that it becomes partially refractory to CFTRinh-172. Login to comment

[hide] Comparison of the gating behaviour of human and mu... J Physiol. 1998 Apr 15;508 ( Pt 2):379-92. Lansdell KA, Delaney SJ, Lunn DP, Thomson SA, Sheppard DN, Wainwright BJ
Comparison of the gating behaviour of human and murine cystic fibrosis transmembrane conductance regulator Cl- channels expressed in mammalian cells.
J Physiol. 1998 Apr 15;508 ( Pt 2):379-92., 1998-04-15 [PMID:9508803]

Abstract [show]
1. To investigate the function of the murine cystic fibrosis transmembrane conductance regulator (CFTR), a full-length cDNA encoding wild-type murine CFTR was assembled and stably expressed in Chinese hamster ovary (CHO) cells. 2. Like human CFTR, murine CFTR formed Cl- channels that were regulated by cAMP-dependent phosphorylation and intracellular ATP. However, murine CFTR Cl- channels had a reduced single-channel conductance and decreased open probability (Po) compared with those of human CFTR. 3. Analysis of the dwell time distributions of single channels suggested that the reduced Po of murine CFTR was caused by both decreased residence in the open state and transitions to a new closed state, described by an intermediate closed time constant. 4. For both human and murine CFTR, ATP and ADP regulated the rate of exit from the long-lived closed state. 5. 5'-Adenylylimidodiphosphate (AMP-PNP) and pyrophosphate, two compounds that disrupt cycles of ATP hydrolysis, stabilized the open state of human CFTR. However, neither agent locked murine CFTR Cl- channels open, although AMP-PNP increased the Po of murine CFTR. 6. The data indicate that although human and murine CFTR have many properties in common, some important differences in function are observed. These differences could be exploited in future studies to provide new understanding about CFTR.

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218 Consistent with this latter possibility, deletion of nineteen residues from the second intracellular loop (ICL2) promoted transitions to a subconductance state, while the I-V relationships of the mutations S945L and G970R located in ICL3 showed weak outward rectification in contrast to that of wild-type CFTR (Xie, Drumm, Ma & Davis, 1995; Seibert, Linsdell, Loo, Hanrahan, Riordan & Clarke, 1996b). Login to comment

[hide] Structure and function of the CFTR chloride channe... Physiol Rev. 1999 Jan;79(1 Suppl):S23-45. Sheppard DN, Welsh MJ
Structure and function of the CFTR chloride channel.
Physiol Rev. 1999 Jan;79(1 Suppl):S23-45., [PMID:9922375]

Abstract [show]
Structure and Function of the CFTR Chloride Channel. Physiol. Rev. 79, Suppl.: S23-S45, 1999. - The cystic fibrosis transmembrane conductance regulator (CFTR) is a unique member of the ABC transporter family that forms a novel Cl- channel. It is located predominantly in the apical membrane of epithelia where it mediates transepithelial salt and liquid movement. Dysfunction of CFTR causes the genetic disease cystic fibrosis. The CFTR is composed of five domains: two membrane-spanning domains (MSDs), two nucleotide-binding domains (NBDs), and a regulatory (R) domain. Here we review the structure and function of this unique channel, with a focus on how the various domains contribute to channel function. The MSDs form the channel pore, phosphorylation of the R domain determines channel activity, and ATP hydrolysis by the NBDs controls channel gating. Current knowledge of CFTR structure and function may help us understand better its mechanism of action, its role in electrolyte transport, its dysfunction in cystic fibrosis, and its relationship to other ABC transporters.

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168 Although, Xenopus CFTR hadships of the mutations S945L and G970R in ICL3 showed weak outward rectification in contrast to that of wild-type a pattern of gating similar to human CFTR, the human-Xenopus CFTR chimera hX1-6 showed a pattern of gatingCFTR (114, 148). Login to comment

[hide] Ivacaftor potentiation of multiple CFTR channels w... J Cyst Fibros. 2012 May;11(3):237-45. doi: 10.1016/j.jcf.2011.12.005. Epub 2012 Jan 30. Yu H, Burton B, Huang CJ, Worley J, Cao D, Johnson JP Jr, Urrutia A, Joubran J, Seepersaud S, Sussky K, Hoffman BJ, Van Goor F
Ivacaftor potentiation of multiple CFTR channels with gating mutations.
J Cyst Fibros. 2012 May;11(3):237-45. doi: 10.1016/j.jcf.2011.12.005. Epub 2012 Jan 30., [PMID:22293084]

Abstract [show]
BACKGROUND: The investigational CFTR potentiator ivacaftor (VX-770) increased CFTR channel activity and improved lung function in subjects with CF who have the G551D CFTR gating mutation. The aim of this in vitro study was to determine whether ivacaftor potentiates mutant CFTR with gating defects caused by other CFTR gating mutations. METHODS: The effects of ivacaftor on CFTR channel open probability and chloride transport were tested in electrophysiological studies using Fischer rat thyroid (FRT) cells expressing different CFTR gating mutations. RESULTS: Ivacaftor potentiated multiple mutant CFTR forms with defects in CFTR channel gating. These included the G551D, G178R, S549N, S549R, G551S, G970R, G1244E, S1251N, S1255P and G1349D CFTR gating mutations. CONCLUSION: These in vitro data suggest that ivacaftor has a similar effect on all CFTR forms with gating defects and support investigation of the potential clinical benefit of ivacaftor in CF patients who have CFTR gating mutations beyond G551D.

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4 These included the G551D, G178R, S549N, S549R, G551S, G970R, G1244E, S1251N, S1255P and G1349D CFTR gating mutations. Login to comment
23 Other known CFTR gating mutations include G178R, G551S, G970R, G1244E, S1255P, and G1349D [9-11]. Login to comment
39 These included G551D-, G178R-, S549N-, S549R-, G551S-, G970R-, G1244E-, S1251N-, S1255P-, and G1349D-CFTR [4,7,9-11]. Login to comment
46 This analysis showed that, as expected for known CFTR gating mutations (G551D, G178R, G551S, G970R, G1244E, S1255P, and G1349D) [5,9-11], the amount of CFTR delivered to the cell surface was generally similar between CFTR with gating defects and normal CFTR. Login to comment
50 Ivacaftor increased the channel gating of mutant CFTR with defective channel gating The effect of ivacaftor on CFTR channel gating was monitored by quantifying the channel open probability by patch-clamp electrophysiology using membrane patches excised from FRT cells expressing the known CFTR gating mutations, G551D-, G178R-, G551S-, G970R-, G1244E-, S1255P-, or G1349D-CFTR. Login to comment
52 Under these conditions, the baseline CFTR channel open probability of G551D-, G178R-, G551S-, G970R-, G1244E-, S1255P-, and G1349D-CFTR was ≤5% of normal CFTR (Fig. 2, B; Table 1). Login to comment
53 For most mutant CFTR forms, the single channel current amplitude, a measure of channel conductance, was similar to normal CFTR (between 77% and 122% of normal CFTR), although a small but statistically significant difference in single channel current amplitude was observed for S1255P-CFTR (Table 1). Login to comment
58 Ivacaftor enhanced chloride transport through mutant CFTR with defective channel gating The impact of the increase in CFTR channel gating by ivacaftor on total chloride transport was assessed in Ussing chamber studies using FRT cells expressing the known CFTR gating mutations, G551D-, G178R-, G551S-, G970R-, G1244E-, S1255P-, and G1349D-CFTR. Login to comment
71 Patch-clamp studies confirmed that the channel open probability of S549N-, S549R-, and S1251N-CFTR was b5% of normal CFTR, whereas the single channel current amplitude Normal F508del G551D G178R S549N S549R G551S G970R G1244E S1251N S1255P G1349D 0 50 100 150 200 CFTRmRNA (%NormalCFTR) None F508del G551D G178R S549N S549R G551S G970R G1244E S1251N S1255P G1349D 0.0 0.2 0.4 0.6 0.8 1.0 ** * CFTRMaturation (Mature/Total) None F508del G551D G178R S549N S549R G551S G970R G1244E S1251N S1255P G1349D 0 100 200 300 400 ** * * * CFTR Mutations MatureCFTR (%NormalCFTR) A B D C Mature Immature Fig. 1. Login to comment
96 Taken together, these in vitro results provide a rationale for testing the potential benefit of ivacaftor in individuals with CF who have a CFTR gating mutation other than G551D, including the G178R-, S549N-, S549R-, G551S-, G970R-, G1244E-, S1251N-, S1255P, and G1349D CFTR gating mutations. Login to comment
97 Evaluation of CF-associated CFTR mutations that were expected to cause protein alterations in the ATP-binding sites formed by the NBDs indicated that S549N- and S1251N-CFTR also shared similar in vitro functional characteristics with G551D-CFTR and could be classified as CFTR gating mutations. Login to comment
99 The partial reduction in S549R-CFTR maturation was ~27% of A Normal G551D G178R S549N S549R G551S G970R G1244E S1251N S1255P G1349D 0.0 0.2 0.4 0.6 0.8 1.0 0 50 100 150 200 250 Baseline With 10 µM Ivacaftor * * * * * * * * * * * CFTR Mutation ChannelOpenProbability ChannelOpenProbability (%NormalCFTR) B 1pA 3sec + 10 µM Ivacaftor G1349D S1255P G970R G551S G178R G1244E Baseline Normal G551D S1251N S549N S549R Fig. 2. Login to comment
122 These included derivatives of 1,4-dihydropyridine and phenylglycine which potentiated G551D-, G970R-, and G1349D-CFTR to a similar extent as ivacaftor [23,25-26]. Login to comment
123 In contrast, sulfamoyl-4-oxoquinoline-3-carboxamides were weakly effective on G551D-, G970R-, and G1349D-CFTR [26] and phloxine B strongly potentiated G551D-CFTR, but not G1349D-CFTR [22]. Login to comment
128 Single channel current amplitude at 80 mV CFTR channel open probability Baseline With 10 μM ivacaftor Baseline With 10 μM ivacaftor Mutation pA % Normal pA % Normal Po % Normal Po % Normal Normal 0.57±0.03 100 0.63±0.02 111 0.400±0.04 100 0.800±0.04 a 200 G551D 0.46±0.06 81 0.46±0.03 81 0.019±0.01 b 5 0.121±0.035 a 30 G178R 0.59±0.11 103 0.66±0.08 116 0.005±0.001 b 1 0.228±0.022 a 57 S549N 0.55±0.02 97 0.61±0.02 108 0.003±0.010 b 1 0.396±0.119 a 99 S549R 0.45±0.01 b 79 0.55±0.02 a 96 0.004±0.010 b 1 0.143±0.031 a 36 G551S 0.57±0.13 100 0.64±0.02 113 0.010±0.001 b 3 0.337±0.110 a 84 G970R 0.55±0.03 96 0.55±0.03 97 0.001±0.001 b 0 0.245±0.042 a 61 G1244E 0.44±0.11 77 0.54±0.08 94 0.011±0.010 b 3 0.470±0.122 a 118 S1251N 0.54±0.07 95 0.63±0.04 111 0.003±0.010 b 1 0.350±0.03 a 88 S1255P 0.70±0.03 b 122 0.71±0.02 125 0.018±0.016 b 5 0.468±0.168 a 117 G1349D 0.49±0.08 85 0.63±0.06 111 0.019±0.015 b 5 0.315±0.110 a 79 a Significantly different (Pb0.05; paired t-test, n=3-5) compared to baseline levels for each CFTR mutation. Login to comment
130 0 100 200 300 400 -9 -8 -7 -6 -5 -4 G178R G551D G551S 0 S549N S549R Ivacaftor [Log M] 0 100 200 300 400 0 50 100 150 200 -9 -8 -7 -6 -5 -4 G970R G1244E S1255P G1349D 0 S1251N Ivacaftor [Log M] ChlorideTransport (%NormalCFTR) Normal Forskolin G178R G551S G970R G1244E 50 2 1 min S1255P Normal F508del G551D G178R S549N S549R G551S G970R G1244E S1251N S1255P G1349D 0 100 200 300 400 0 50 100 150 200 * * * * * * * * * * * * * CFTR Mutation ChlorideTransport(µA/cm2)ChlorideTransport(µA/cm2) ChlorideTransport(A/cm2) ChlorideTransport (%NormalCFTR) B G1349D G551D A F508del C S549N S549R S1251N Baseline Baseline present study, cause protein alterations in the ATP binding pockets formed by the two NBDs required for normal CFTR channel gating (Fig. 4) [2]. Login to comment
131 The G178R and G970R CFTR gating mutations alter the intracellular cytoplasmic loops that are believed to link the ATP-driven conformational changes in the NBDs to the opening of the CFTR channel pore formed by the membrane spanning domains [27]. Login to comment
144 The in vitro data presented here suggest that ivacaftor has a similar effect on all CFTR forms with gating defects and support the investigation of ivacaftor in patients with CF who have CFTR gating mutations beyond G551D, including G178R, S549N, S549R, G551S, G970R, G1244E, S1251N, S1255P, and G1349D. Login to comment
24 Other known CFTR gating mutations include G178R, G551S, G970R, G1244E, S1255P, and G1349D [9-11]. Login to comment
40 These included G551D-, G178R-, S549N-, S549R-, G551S-, G970R-, G1244E-, S1251N-, S1255P-, and G1349D-CFTR [4,7,9-11]. Login to comment
47 This analysis showed that, as expected for known CFTR gating mutations (G551D, G178R, G551S, G970R, G1244E, S1255P, and G1349D) [5,9-11], the amount of CFTR delivered to the cell surface was generally similar between CFTR with gating defects and normal CFTR. Login to comment
51 Ivacaftor increased the channel gating of mutant CFTR with defective channel gating The effect of ivacaftor on CFTR channel gating was monitored by quantifying the channel open probability by patch-clamp electrophysiology using membrane patches excised from FRT cells expressing the known CFTR gating mutations, G551D-, G178R-, G551S-, G970R-, G1244E-, S1255P-, or G1349D-CFTR. Login to comment
59 Ivacaftor enhanced chloride transport through mutant CFTR with defective channel gating The impact of the increase in CFTR channel gating by ivacaftor on total chloride transport was assessed in Ussing chamber studies using FRT cells expressing the known CFTR gating mutations, G551D-, G178R-, G551S-, G970R-, G1244E-, S1255P-, and G1349D-CFTR. Login to comment
72 Patch-clamp studies confirmed that the channel open probability of S549N-, S549R-, and S1251N-CFTR was b5% of normal CFTR, whereas the single channel current amplitude Normal F508del G551D G178R S549N S549R G551S G970R G1244E S1251N S1255P G1349D 0 50 100 150 200 CFTR mRNA (% Normal CFTR) None F508del G551D G178R S549N S549R G551S G970R G1244E S1251N S1255P G1349D 0.0 0.2 0.4 0.6 0.8 1.0 ** * CFTR Maturation (Mature/Total) None F508del G551D G178R S549N S549R G551S G970R G1244E S1251N S1255P G1349D 0 100 200 300 400 ** * * * CFTR Mutations Mature CFTR (% Normal CFTR) A B D C Mature Immature Fig. 1. Login to comment
100 The partial reduction in S549R-CFTR maturation was ~27% of A Normal G551D G178R S549N S549R G551S G970R G1244E S1251N S1255P G1349D 0.0 0.2 0.4 0.6 0.8 1.0 0 50 100 150 200 250 Baseline With 10 &#b5;M Ivacaftor * * * * * * * * * * * CFTR Mutation Channel Open Probability Channel Open Probability (% Normal CFTR) B 1pA 3sec + 10 &#b5;M Ivacaftor G1349D S1255P G970R G551S G178R G1244E Baseline Normal G551D S1251N S549N S549R Fig. 2. Login to comment
124 In contrast, sulfamoyl-4-oxoquinoline-3-carboxamides were weakly effective on G551D-, G970R-, and G1349D-CFTR [26] and phloxine B strongly potentiated G551D-CFTR, but not G1349D-CFTR [22]. Login to comment
129 Single channel current amplitude at 80 mV CFTR channel open probability Baseline With 10 bc;M ivacaftor Baseline With 10 bc;M ivacaftor Mutation pA % Normal pA % Normal Po % Normal Po % Normal Normal 0.57&#b1;0.03 100 0.63&#b1;0.02 111 0.400&#b1;0.04 100 0.800&#b1;0.04 a 200 G551D 0.46&#b1;0.06 81 0.46&#b1;0.03 81 0.019&#b1;0.01 b 5 0.121&#b1;0.035 a 30 G178R 0.59&#b1;0.11 103 0.66&#b1;0.08 116 0.005&#b1;0.001 b 1 0.228&#b1;0.022 a 57 S549N 0.55&#b1;0.02 97 0.61&#b1;0.02 108 0.003&#b1;0.010 b 1 0.396&#b1;0.119 a 99 S549R 0.45&#b1;0.01 b 79 0.55&#b1;0.02 a 96 0.004&#b1;0.010 b 1 0.143&#b1;0.031 a 36 G551S 0.57&#b1;0.13 100 0.64&#b1;0.02 113 0.010&#b1;0.001 b 3 0.337&#b1;0.110 a 84 G970R 0.55&#b1;0.03 96 0.55&#b1;0.03 97 0.001&#b1;0.001 b 0 0.245&#b1;0.042 a 61 G1244E 0.44&#b1;0.11 77 0.54&#b1;0.08 94 0.011&#b1;0.010 b 3 0.470&#b1;0.122 a 118 S1251N 0.54&#b1;0.07 95 0.63&#b1;0.04 111 0.003&#b1;0.010 b 1 0.350&#b1;0.03 a 88 S1255P 0.70&#b1;0.03 b 122 0.71&#b1;0.02 125 0.018&#b1;0.016 b 5 0.468&#b1;0.168 a 117 G1349D 0.49&#b1;0.08 85 0.63&#b1;0.06 111 0.019&#b1;0.015 b 5 0.315&#b1;0.110 a 79 a Significantly different (Pb0.05; paired t-test, n=3-5) compared to baseline levels for each CFTR mutation. Login to comment
132 The G178R and G970R CFTR gating mutations alter the intracellular cytoplasmic loops that are believed to link the ATP-driven conformational changes in the NBDs to the opening of the CFTR channel pore formed by the membrane spanning domains [27]. Login to comment
145 The in vitro data presented here suggest that ivacaftor has a similar effect on all CFTR forms with gating defects and support the investigation of ivacaftor in patients with CF who have CFTR gating mutations beyond G551D, including G178R, S549N, S549R, G551S, G970R, G1244E, S1251N, S1255P, and G1349D. Login to comment

[hide] Stimulation of murine intestinal secretion by dail... Cell Physiol Biochem. 2011;28(2):239-50. Epub 2011 Aug 16. Al-Nakkash L, Batia L, Bhakta M, Peterson A, Hale N, Skinner R, Sears S, Jensen J
Stimulation of murine intestinal secretion by daily genistein injections: gender-dependent differences.
Cell Physiol Biochem. 2011;28(2):239-50. Epub 2011 Aug 16., [PMID:21865731]

Abstract [show]
Background/Aims: The effect of daily injections with genistein (naturally occurring phytoestrogen) on intestinal chloride (Cl(-)) secretion was measured with Ussing chamber short circuit current (I(sc), muA/cm(2)), in C57BL/6J male and female mice, using 600 mg/kg genistein/day (600G), 300 mg/kg genistein/day (300G), 150 mg/kg genistein/day (150G) or genistein-free vehicle control (0G) for 1- or 2-weeks. Methods and Results: Injecting with 600G elicited significant increases in basal I(sc) in females after 1-week (n70 muA/cm(2), n=15, p < 0.05) and in males after 2-weeks (n80 muA/cm(2), n=5, p < 0.05) compared to their 0G counterparts. Chloride-free ringer significantly reduced basal I(sc) by 65% in 600G males and 72% in 600G females, suggesting that Cl(-) was the major anion comprising the genistein-stimulated secretion. The forskolin-stimulated (10 muM) I(sc) was significantly inhibited by the CFTR chloride channel inhibitors, glibenclamide (500 muM) and CFTR(inh)-172 (100 muM) in 600G males and females, suggesting some contribution by genistein-dependent CFTR-mediated Cl(-) secretion. We found no associated changes in intestinal morphology, nor change in total CFTR protein with 600G. There was a 5% increase in apical/subapical ratio in 600G males compared to controls (no change in females). Conclusion: These data suggest that male and female mice both exhibit increased Cl- secretion with 600G, however, the mechanisms mediating this are gender-dependent.

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239 The idea of mutation specific correctors was verified by Caputo et al. [51] whose results suggested that felodipine and the phenyglycine PG-01, exerted a wider pharmacological effect (acting on CFTR mutations E193K, G970R and G551D) compared to the lesser potentiative sulfonamide SF-01. Login to comment

[hide] Validation of high-resolution DNA melting analysis... J Mol Diagn. 2008 Sep;10(5):424-34. Epub 2008 Aug 7. Audrezet MP, Dabricot A, Le Marechal C, Ferec C
Validation of high-resolution DNA melting analysis for mutation scanning of the cystic fibrosis transmembrane conductance regulator (CFTR) gene.
J Mol Diagn. 2008 Sep;10(5):424-34. Epub 2008 Aug 7., [PMID:18687795]

Abstract [show]
High-resolution melting analysis of polymerase chain reaction products for mutation scanning, which began in the early 2000s, is based on monitoring of the fluorescence released during the melting of double-stranded DNA labeled with specifically developed saturation dye, such as LC-Green. We report here the validation of this method to scan 98% of the coding sequence of the cystic fibrosis transmembrane conductance regulator (CFTR) gene. We designed 32 pairs of primers to amplify and analyze the 27 exons of the gene. Thanks to the addition of a small GC-clamp at the 5' ends of the primers, one single melting domain and one identical annealing temperature were obtained to co-amplify all of the fragments. A total of 307 DNA samples, extracted by the salt precipitation method, carrying 221 mutations and 21 polymorphisms, plus 20 control samples free from variations (confirmed by denaturing high-performance liquid chromatography analysis), was used. With the conditions described in this study, 100% of samples that carry heterozygous mutations and 60% of those with homozygous mutations were identified. The study of a cohort of 136 idiopathic chronic pancreatitis patients enabled us to prospectively evaluate this technique. Thus, high-resolution melting analysis is a robust and sensitive single-tube technique for screening mutations in a gene and promises to become the gold standard over denaturing high-performance liquid chromatography, particularly for highly mutated genes such as CFTR, and appears suitable for use in reference diagnostic laboratories.

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63 Continued Exon Primer Sequences GC length Amplicon length (bp) Introns Number of heterozygous- positive controls Number of homozygous- positive controls Recommended control 16 LSCFE16Fmod 5Ј-CCGCTGAATGCGTCTACTGTGATCCA-3Ј 3 299 bp 77 6 G970R LSCFE16Rmod 5Ј-CCGTAGACAGGACTTCAA CCCTCAATCAA-3Ј 3 87 3120ϩ1GϾA 17a LSCFE17AFmod 5Ј-CCGCCGGACACACTTTG TCCACTT-3Ј 6 286 bp 49 13 3121-1GϾA LSCFE17ARmod 5Ј-CCGCCGTCAAATAGCTCTTATAGCTTTTTT ACAAGATG-3Ј 6 25 I1027T 17b LSCF17BAFmod 5Ј-CCGCCGCCCCGCCGTCAGGTACA AGATATTATG-3Ј 14 56 11 3272-26AϾG LSCF17BARmod 5Ј-CCGCCGCCGCAGTGTTGACAGGT ACAAGAAC-3Ј 7 247 bp A1067T LSCF17BBFmod 5Ј-CCGCCCTTACTTTGAAACTCTGTT CCACAAAGC-3Ј 4 247 bp T1095T LSCF17BBRmod 5Ј-CCGCCGTTGATAACCTATAGAATG CAG-3Ј 6 62 E1104X 18 LSCFE18Fmod 5Ј-CCGCCGAGTCGTTCACAGAAGA GAGAAATAAC-3Ј 6 236 bp 34 2 D1152H LSCFE18Rmod 5Ј-CCGCCGCCGCGGTACTTTGTT ACTTGTCTGAATTTTTTT-3ЈCATAA 12 25 3547delA 19 LSCF19i5mod 5Ј-CCGCCGCCGCGCATCAAACTA ATTGTGAAATTGTCTGCC-3Ј 10 408 bp 73 10 S1235R LSCF19i3mod 5Ј-CCGCCGCCGCACACATTGCT TCAGGCTACTGGGA-3Ј 11 49 R1162L 20 LSCF20i5mod 5Ј-CCGCCGCCGCCGCTACTGAATTATGT TTATGGCATGG-3Ј 13 323 bp 44 13 W1282X LSCF20i3mod 5Ј-CCGCCGCCGCTCTTGAGTACAAGTA TCAAATAGCAG-3Ј 10 50 4005ϩ33GϾA 21 LSCFe21F 5Ј-CCGCCGCCGCGCAAGTTATTCATA CTTTCTTCTTCTTT-3Ј 12 217 bp 15 5 1 N1303K LSCFe21R 5Ј-CCGCCGCCGCTATATCAGCCA TTTGTG-3Ј 8 47 Q1313X 22 LSCFe22FmodC LSCFe22 RmodD 5Ј-CCGCCGAGAATGTCAAC TGCTTGAGTGT-3Ј 6 311 bp 41 2 R1358S 5Ј-CCGCCGGCAGGCATAATGA TTCTGTTCCCAC-3Ј 10 51 I1366T 23 LSCFE23Fmod 5Ј-CCGCCGCCGCAAGGTAAAT ACAGATCAT-3Ј 9 259 bp 44 3 4374ϩ1GϾT 4374ϩ13AϾG LSCFE23Rmod: 5Ј-CCGGCAGGAACTATCACAT GTGAGATTG-3Ј 3 53 24 LSCFE24FmodB 5Ј-CCGCCGCTTTGAGCCTGT GCCAGTTTCTGT-3Ј 6 378 bp 58 5 1 Q1463Q LSE24RmodB 5Ј-CCGCCGACGAGCTCCAATTC CATGAGGTGA-3Ј 6 62 Y1424Y the same technique: the majority of our samples were extracted by a classical saline technique or an automated extraction and their quality was adequate. Login to comment

[hide] Spectrum of CFTR mutations in cystic fibrosis and ... Hum Mutat. 2000;16(2):143-56. Claustres M, Guittard C, Bozon D, Chevalier F, Verlingue C, Ferec C, Girodon E, Cazeneuve C, Bienvenu T, Lalau G, Dumur V, Feldmann D, Bieth E, Blayau M, Clavel C, Creveaux I, Malinge MC, Monnier N, Malzac P, Mittre H, Chomel JC, Bonnefont JP, Iron A, Chery M, Georges MD
Spectrum of CFTR mutations in cystic fibrosis and in congenital absence of the vas deferens in France.
Hum Mutat. 2000;16(2):143-56., [PMID:10923036]

Abstract [show]
We have collated the results of cystic fibrosis (CF) mutation analysis conducted in 19 laboratories in France. We have analyzed 7, 420 CF alleles, demonstrating a total of 310 different mutations including 24 not reported previously, accounting for 93.56% of CF genes. The most common were F508del (67.18%; range 61-80), G542X (2.86%; range 1-6.7%), N1303K (2.10%; range 0.75-4.6%), and 1717-1G>A (1.31%; range 0-2.8%). Only 11 mutations had relative frequencies >0. 4%, 140 mutations were found on a small number of CF alleles (from 29 to two), and 154 were unique. These data show a clear geographical and/or ethnic variation in the distribution of the most common CF mutations. This spectrum of CF mutations, the largest ever reported in one country, has generated 481 different genotypes. We also investigated a cohort of 800 French men with congenital bilateral absence of the vas deferens (CBAVD) and identified a total of 137 different CFTR mutations. Screening for the most common CF defects in addition to assessment for IVS8-5T allowed us to detect two mutations in 47.63% and one in 24.63% of CBAVD patients. In a subset of 327 CBAVD men who were more extensively investigated through the scanning of coding/flanking sequences, 516 of 654 (78. 90%) alleles were identified, with 15.90% and 70.95% of patients carrying one or two mutations, respectively, and only 13.15% without any detectable CFTR abnormality. The distribution of genotypes, classified according to the expected effect of their mutations on CFTR protein, clearly differed between both populations. CF patients had two severe mutations (87.77%) or one severe and one mild/variable mutation (11.33%), whereas CBAVD men had either a severe and a mild/variable (87.89%) or two mild/variable (11.57%) mutations.

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105 d G149R, S489X, S492F, S549R, 1898+1G>A, 2622+1G>A, G970R, R1066H, W1204X, 3850-1G>A, Q1313X. Login to comment

[hide] Cytoplasmic loop three of cystic fibrosis transmem... J Biol Chem. 1996 Nov 1;271(44):27493-9. Seibert FS, Linsdell P, Loo TW, Hanrahan JW, Riordan JR, Clarke DM
Cytoplasmic loop three of cystic fibrosis transmembrane conductance regulator contributes to regulation of chloride channel activity.
J Biol Chem. 1996 Nov 1;271(44):27493-9., [PMID:8910333]

Abstract [show]
To examine the contribution of the large cytoplasmic loops of the cystic fibrosis transmembrane conductance regulator (CFTR) to channel activity, the three point-mutations (S945L, H949Y, G970R) were characterized that have been detected in the third cytoplasmic loop (CL3, residues 933-990) in patients with cystic fibrosis. Chinese hamster ovary cell lines stably expressing wild-type CFTR or mutant G970R-CFTR yielded polypeptides with apparent masses of 170 kDa as the major products, whereas the major products of mutants S945L-CFTR and H949Y-CFTR had apparent masses of 150 kDa. The 150-kDa forms of CFTR were sensitive to endoglycosidase H digestion, indicating that these mutations interfered with maturation of the protein. Increased levels of mature CFTR (170 kDa) could be obtained for mutant H949Y when cells were grown at a lower temperature (26 degrees C) or incubated in the presence of 10% glycerol. For all mutants, the open probability (P0) of the CFTR channels was significantly altered. S945L-CFTR and G970R-CFTR showed a severe reduction in the P0, whereas the H949Y mutation doubled the P0 relative to wild-type. The changes in P0 predominantly resulted from an alteration of the mean burst durations which suggests that CL3 is involved in obtaining and/or maintaining stability of the open state. In addition, mutants S945L and G970R had current-voltage relationships that were not completely linear over the range +/-80 mV, but showed slight outward rectification. The fact that CL3 mutations can have subtle effects on channel conductance indicates that this region may be physically close to the inner mouth of the pore.

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0 Cytoplasmic Loop Three of Cystic Fibrosis Transmembrane Conductance Regulator Contributes to Regulation of Chloride Channel Activity* (Received for publication, May 3, 1996, and in revised form, August 22, 1996) Fabian S. Seibert‡, Paul Linsdell§¶, Tip W. Loo, John W. Hanrahan§ʈ, John R. Riordan**‡‡, and David M. Clarke§§ From the Medical Research Council Group in Membrane Biology, Departments of Medicine and Biochemistry, University of Toronto, Toronto, Ontario, Canada, M5S 1A8, the §Department of Physiology, McGill University, Montreal, Quebec, Canada, H3G 1Y6, and the **Mayo Graduate School of Medicine and Department of Biochemistry and Molecular Biology, S. C. Johnson Medical Research Center, Mayo Clinic Scottsdale, Scottsdale, Arizona 85259 To examine the contribution of the large cytoplasmic loops of the cystic fibrosis transmembrane conductance regulator (CFTR) to channel activity, the three point-mutations (S945L, H949Y, G970R) were characterized that have been detected in the third cytoplasmic loop (CL3, residues 933-990) in patients with cystic fibrosis. Login to comment
1 Chinese hamster ovary cell lines stably expressing wild-type CFTR or mutant G970R-CFTR yielded polypeptides with apparent masses of 170 kDa as the major products, whereas the major products of mutants S945L-CFTR and H949Y-CFTR had apparent masses of 150 kDa. Login to comment
5 S945L-CFTR and G970R-CFTR showed a severe reduction in the P0, whereas the H949Y mutation doubled the P0 relative to wild-type. Login to comment
7 In addition, mutants S945L and G970R had current-voltage relationships that were not completely linear over the range ؎80 mV, but showed slight outward rectification. Login to comment
35 The aim of the present study was to examine the functional significance of a previously uninvestigated domain, CL3 (predicted residues: 933-990, connecting TMs 8 and 9 of CFTR; Fig. 1), by characterizing the three different point-mutations that have been identified in CL3 from patients with CF (S945L (Claustres et al., 1993), H949Y (Ghanem et al., 1994), and G970R (Cuppens et al., 1993)). Login to comment
54 Western blotting with the CFTR-specific monoclonal antibody M3A7 (Kartner et al., 1992) demonstrated that wild-type and G970R-mutant CFTRs yielded fully mature protein (170 kDa, band C) as the major product, whereas mutants S945L and H949Y yielded little of the mature form (Fig. 2). Login to comment
71 For G970R-CFTR, a forskolin-induced efflux was almost absent, despite the large amounts of complex glycosylated protein observed in Western blotting. Login to comment
79 It was apparent that G970R allowed the production of fully glycosylated CFTR, but that there was little anion channel activity in the cells expressing this mutant. Login to comment
81 Using this approach, it was observed that similar amounts of mature forms of G970R-CFTR and wild-type protein were biotinylated (Fig. 5). Login to comment
83 This showed that G970R-CFTR did reach the cell surface and therefore must be severely impaired in function to explain the very low level of iodide efflux observed. Login to comment
84 The absence of function is likely to be the cause of the CF symptoms in patients affected by the G970R mutation. Login to comment
90 Therefore, the loss of CFTR activity observed with the mutation G970R appears to be due to the presence of a positive charge at this site. Login to comment
116 For each mutant, however, the level of channel activity was clearly different from wild-type CFTR (Fig. 7); both S945L and G970R channels showed a lower level of activity than wild-type, while for H949Y-CFTR activity appeared to be higher than wild-type. Login to comment
117 This was confirmed by channel mean open probability (P0) measurements; S945L-CFTR and G970R-CFTR had significantly lower mean P0 values than wild-type channels, and the mean P0 of H949Y channels was significantly greater than observed for wild-type (Fig. 8A). Login to comment
122 Both S945L and G970R mutants, however, had I-V relationships which were not completely linear over this voltage range, but instead showed slight outward rectification (Fig. 9, A and C). Login to comment
123 In S945L-CFTR, this outward rectification was due to a significant reduction in current at negative membrane potentials compared to the wild-type channel (Fig. 9, A and D), while in G970R outward rectification resulted from increased current at positive potentials (Fig. 9, C and D). Login to comment
125 The reasons for the outward rectification seen in both S945L and G970R are unclear; however, the fact that CL3 mutations can have subtle effects on channel conductance suggests that this region may be physically located close to the inner mouth of the CFTR chloride channel pore. Login to comment
128 The most striking effect due to the amino acid substitutions was a drastically altered P0 of the mutant CFTRs relative to wild-type CFTR, with S945L and G970R decreasing the P0 of the channel and H949Y doubling its P0. Login to comment
131 Within the framework of this model, the altered duration of the open state observed in the present study indicates that mutations in CL3 can affect events at NBF2 or affect communication from NBF2 to the pore. Mutations within CL3 can have opposite effects of either prolonging (H949Y) or dramatically decreasing (S945L, G970R) the duration of the open state. Login to comment
145 tances due to mutations S945L and G970R show that mutagenesis of residues in CL3 has a subtle influence on pore properties, suggesting that CL3 may contribute to a region around the inner mouth of the pore. Login to comment
161 Examples of wild-type, S945L, H949Y, and G970R CFTR channel currents recorded from inside-out patches at a membrane potential of -30 mV. Login to comment
168 iodide efflux provides an efficient tool to identify gross alterations in CFTR channel activity, but the quantitative details are best evaluated by more subtle techniques such as single-channel patch-clamping. However, for low activity channels such as G970R-CFTR, which give little iodide efflux, the P0 may somewhat overestimate residual channel activity since only open channels can be observed electrophysiologically whereas channels which never open during the course of the experiment will be missed. Login to comment
174 The significant decrease in CFTR function due to the G970R mutation is consistent with this point of view, since the loss of activity was due to the charge rather than size of the introduced Arg. Login to comment
175 This, and the observation that mature G970R-CFTR is properly trafficked to the plasma membrane, suggests that G970R affects activity through an altered electrostatic interaction within the protein or with other molecules rather than a gross change in CFTR structure. Login to comment
34 The aim of the present study was to examine the functional significance of a previously uninvestigated domain, CL3 (predicted residues: 933-990, connecting TMs 8 and 9 of CFTR; Fig. 1), by characterizing the three different point-mutations that have been identified in CL3 from patients with CF (S945L (Claustres et al., 1993), H949Y (Ghanem et al., 1994), and G970R (Cuppens et al., 1993)). Login to comment

[hide] Sensitivity of single-strand conformation polymorp... Hum Mol Genet. 1994 May;3(5):801-7. Ravnik-Glavac M, Glavac D, Dean M
Sensitivity of single-strand conformation polymorphism and heteroduplex method for mutation detection in the cystic fibrosis gene.
Hum Mol Genet. 1994 May;3(5):801-7., [PMID:7521710]

Abstract [show]
The gene responsible for cystic fibrosis (CF) contains 27 coding exons and more than 300 independent mutations have been identified. An efficient and optimized strategy is required to identify additional mutations and/or to screen patient samples for the presence of known mutations. We have tested several different conditions for performing single-stranded conformation polymorphism (SSCP) analysis in order to determine the efficiency of the method and to identify the optimum conditions for mutation detection. Each exon and corresponding exon boundaries were amplified. A panel of 134 known CF mutations were used to test the efficiency of detection of mutations. The SSCP conditions were varied by altering the percentage and cross-linking of the acrylamide, employing MDE (an acrylamide substitute), and by adding sucrose and glycerol. The presence of heteroduplexes could be detected on most gels and in some cases contributed to the ability to distinguish certain mutations. Each analysis condition detected 75-98% of the mutations, and all of the mutations could be detected by at least one condition. Therefore, an optimized SSCP analysis can be used to efficiently screen for mutations in a large gene.

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121 1078delT (35), L327R (Ravnik-Glavac a al., unpublished), R334W (36), D36K (31), R347L (26), R347P (14), A349V (26), R352Q (30), 1221delCT (34); Exon 8: W401X (31), 1342-1G-C (25); Exon 9: G458V (37), 1525 -1G-A (38); Exon 10: S492F (34), Q493X (39), 1609delCA (40,17), deltaI507 (39,41), deltaF5O8 (3), 1717-1G-A (39,42); Exon 11: G542X (39), S549N, G551D, R553X (43), R553Q (44), A559T (43), R560K (Fine et al., pers. comm.), R560T (39); Exon 12: Y563N (39), 1833delT (Schwartz et al., pers. comm.), P574H (39), 1898 + 1G-C (31), 1898+3A-G (Ferrari et al., pers. comm.); Exon 13: G628R(G-C) (31), Q685X (Firec et al., pers. comm.), K716X (26), L719X (Dork etal., pers. comm.), 2522insC (15), 2556insAT (45), E827X (34); Exon 14a: E831X (Ffrec et al., pers. comm.), R851X (29), 2721delll (31), C866Y (Audrezet et al., pers. comm.); Exon 14b: 2789+5G-A (Highsmith et al., pers. comm.); Exon 15: 2907denT (21), 2991del32 (Dark and TQmmler, pers. comm.), G970R (31); Exon 16: S977P, 3100insA (D6rk et al., pers. comm.); Exon 17a: I1005R (Dork and TQmmler, pers. comm.), 3272-1G-A (46); Exon 17b: H1054D (F6rec et al., pers. comm.), G1061R (Fdrec et al., pers. comm.), 332Oins5, R1066H, A1067T (34), R1066L (Fe"rec etal., pers. comm.), R1070Q (46), E1104X (Zielenski el al., pers. comm.), 3359delCT (46), L1077P (Bozon « a/., pers. comm.), H1085R (46), Y1092X (Bozon etal., pers. comm.), W1098R, M1101K (Zielenski et al., pers. comm.); Exon 18: D1152H (Highsmith et al., pers. comm.); Exon 19:R1162X (36), 3659delC (39), 3662delA (25), 3667del4 (Chillon et al., pers. comm.), 3737ddA (35), 3821ddT (15), I1234V (35), S1235R (31), Q1238X (26), 3849G-A (25), 385O-3T-G (38); Exon20:3860ins31 (Chillon etal., pers. comm.), S1255X (47), 3898insC (26), 3905insT (Malik et al., pers. comm.), D127ON (48), W1282X (49), Q1291R (Dork et al., pers. comm.), Exon 21: N1303H (35), N13O3K (50), W1316X (43); Exon 22: 11328L/4116delA (Dork and TQmmler, pers. comm.), E1371X (25); Exon 23: 4374+ 1G-T (38); Exon 24: 4382delA (Claustres et al., pers. comm.). Login to comment

[hide] CFTR haplotype backgrounds on normal and mutant CF... Hum Mol Genet. 1994 Apr;3(4):607-14. Cuppens H, Teng H, Raeymaekers P, De Boeck C, Cassiman JJ
CFTR haplotype backgrounds on normal and mutant CFTR genes.
Hum Mol Genet. 1994 Apr;3(4):607-14., [PMID:7520797]

Abstract [show]
Ten polymorphic loci, located in a 1 Mb interval across the cystic fibrosis locus, were analyzed on normal and mutant CFTR genes. A different distribution of haplotype backgrounds among normal and mutant CFTR genes was observed. With exception of the D7S8 locus, the three most common mutations, delta F508, G542X and N1303K, were found on an identical haplotype background. In agreement with the observed linkage equilibrium between the Q1463Q and D7S8 loci, both alleles at the D7S8 locus were found on delta F508 CFTR genes. However, the G542X and N1303K mutations, which have been estimated to be at least 35000 years old, were found to be associated with a single allele at the D7S8 locus. Absence of recombination between the D7S8 and Q1463Q loci was also observed on normal CFTR genes with this haplotype background. At the Tn locus in intron 8, allele 9 known to result in very efficient splicing was associated with the most frequent mutations. At the M470V locus, located in a conserved region of the first nucleotide binding fold, the amino acid methionine was found to be associated with the frequent mutations, in particular with mutations located in one of the two nucleotide binding folds which are generally known as severe mutations with regard to exocrine pancreatic function. On mutant CFTR gene, this locus was in complete association with the centromeric D9 locus, in the absence of a complete association with the intervening loci.(ABSTRACT TRUNCATED AT 250 WORDS)

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34 Distribution of alleles at 10 polymorphic loci Locus Allele Normal Mutant Mutations XV2c KM19 D9 1 2 1 2 1 2 58 (0.492) 60 (0.508) 84 (0.622) 51 (0.378) 78 (0.586) 55 (0.414) 146 (0.918) 13 (0.082) 19(0.109) 156 (0.891) 15 (0.085) 161 (0.915) 1001 + llC/T Tn 115 (0.927) R 9 (0.073) 5 7 (0.057) 7 102 (0.836) 9 13 (0.107) M470V C 62 (0.496) R 63 (0.504) 1898+15 2T/A C 84(0.641) R 47 (0.359) T854T Q1463Q D7S8 C 82 (0.636) R 47 (0.364) C 90 (0.692) R 40 (0.308) 1 38 (0.317) 2 82 (0.683) 33 (0.192) 139 (0.808) 0 (0.000) 32 (0.190) 136 (0.810) 156 (0.902) 17 (0.098) 163 (0.926) 13 (0.074) 162 (0.926) 13 (0.074) 162 (0.931) 12 (0.069) 91 (0.569) 69 (0.431) E60X, 622-2A-C, A455E, AF508 (98.3%), 1717-1G-A, G542X, 0.479 63.54 G628R(G-C)/S1235R,2183AA-G, G970R, W1282X, N1303K p<10~ G458V, AI5O7, AF508 (1.7%), 1898 + 1G-C, E73OX, 3272-26A-G, W1310X, 4218insT, UA, UB, UC I336K, W401X, 2T2ldelll, Y1092X, 3659delC, S1251N: not included (5%) E60X, 622-2A-C, W401X, G458V, AF5O8 (1.6%), 1898+ 1G-C, -0.541 90.63 G628R(G-Q/S1235R, E730X, G970R, 3272-26A-G (50.0%), p<10" Y1092X, 3659delC, S1251N, W1310X, UB, UTC A455E, AI507, AF5O8 (98.4%), 1717- 1G-A, G542X, 2183AA-G, 3272-26A-G (50.0%), W1282X, N13O3K, 4218insT, UA 1336K, 2721delU: not included (1%) E60X, 622-2A-C, W401X, G458V, 1898 +1G-C, E730X, G970R, -0.541 90.46 Y1092X, 3659delC, S1251N, W1310X, UB, UC p<10" A455E, AI507, AF508, 1717- 1G-A, G542X, G628R(G-Q/S1235R, 2183AA-G, 3272-26A-G, W1282X, N13O3K, 4218insT, UA I336K, 2721delll: not included (1%) E60X, 622-2A-C, I336K, W401X, G458V, AI507, 1717- 1G-A, -0.726 155.94 1898 + 1G-C, G628R(G-C)/S1235R, 2183AA-G, E730X, 2721delll, p< 10" G970R, 3272-26A-G, Y1092X, 3659delC, S1251N, W1282X, W1310X, 4218insT, UA, UB, UC A455E, AF5O8, G542X, N13O3K E60X, 622-2A-C, I336K, W401X, G458V, AI507, 1717-1G-A, 1898 + 1G-C, G628R(G-C)/S1235R, 2183AA-G, E730X, 2721delll, G970R, 3272-26A-G, Y1092X, 3659delC, S1251N, W1282X, W1310X, 4218insT, UA, UB, UC A455E, AF5O8, G542X, N13O3K A455E, AI5O7, AF508, 1717-1G-A, G542X, G628R(G-Q/S1235R, 2183AA-G, 3272-26A-G, W1282X, N13O3K, 4218insT, UA E60X, 622-2A-C, W401X, G458V, 1898 + 1G-C, E730X, G970R, Y1092X, 3659delC, S1251N, W1310X, UB, UC 1336K, midclll: not included (1%) E60X, 622-2A-C, W401X, A455E, G458V, AF508 (99.2%), G542X, 1898 + 1G-C, 2183AA-G, E730X, G970R, Y1092X, 3659delC, S1251N, N1303K, W1310X, UB, UC AI507, AF5O8 (0.8%), 1717-1G-A, G628R(G-Q/S1235R, 3272-26A-G, W1282X, 4218insT, UA I336K, 2721delU: not included (1%) E60X, 622-2A-C, W401X, A455E, G458V, AF508 (99.2%), G542X, 1898+1G-C, 2183AA-G, E730X, G970R, Y1092X, 3659delC,S1251N, N13O3K, W1310X, UB, UC AI507, AF508 (0.8%), 1717-1G-A, G628R(G-C)/S1235R, 3272-26A-G, W1282X, 4218insT, UA 1336K, midelll: not included (1%) E60X, 622-2A-C, W401X, A455E, G458V, AF5O8 (99.2%), G542X, G628R(G-Q/S1235R, 2183AA-G, E730X, G970R, Y1092X, 3659delC, S1251N,N1303K, W1310X, UC AI507, AF5O8 (0.8%), 1717-1G-A, 1898 + 1G-C, 3272-26A-G, W1282X, 4218insT 1336K, 2721del11. Login to comment
35 UA, UB: not included (2%) A455E, AF508 (61.2%), 1717-1G-A (66.7%), G542X, G628R(G-C)/S1235R, 3272-26A-G, S1251N, W1282X, W1310X E60X, 622-2A-C, W401X, G458V, AJ507, AF5O8 (38.8%), 1717- 1G-A (33.3%), 1898 +1G-C, 2183AA-G, E730X, G970R, Y1092X, 3659delC, N13O3K, 4218insT, UA, UB, UC 1336K, 2721delll: not included (1%) -0.694 139.81 p<10~ 0.452 60.83 p<10" 0.355 38.77 p<10" 0.360 39.44 p<10~7 0.314 29.91 0.250 17.54 p<10"4 The observed CFTR genes associated with a particular allele are given, proportions are given between brackets. Not all the mutations were informative for each of the tested loci, which were therefore not included. For the Tn locus the standardized linkage disequilibrium coefficient was calculated for the group of the non-T9 alleles and the T9 alleles. Login to comment
72 Extragenic (XV2c/KM19/D9) haplotypes Haplotype Normal Mutant Mutations 111 211 121 112 212 122 222 23 (0.204) 43 (0.381) 2 (0.018) 6 (0.053) 0 (0.000) 22 (0.195) 17 (0.150) 4 (0.026) E60X, 622-2A-C, G970R 6 (0.039) G458V, 1898+1G-C, E73OX, W1310X, UB, UC 0 (0.000) 3 (0.019) AF5O8 (1.7%), G628R(G-Q/S1235R 1 (0.006) 3272-26A-G (50.0%) 134 (0.870) A455E, AF508 (96.5%), 1717-1G-A, G542X, 2183AA-G, W1282X, N13O3K 6 (0.039) AI507, AF508 (1.8%), 3272-26A-G (50.0%), 4218insT, UA p<10"3 p<10"7 p<10~7 p<10"2 The observed CFTR genes associated with a particular haplotype are given, proportions are given between brackets. Login to comment
103 CFTR haplocypes I II ma mb rv V VI Haplotype C7RCCC 211C7RCCC1 111C7RCCC1 /11C7RCCC1 211C7RCCC2 111C7RCCC2 /11C7RCCC2 122C7RCCC2 121C7RCCC2 C5CRRR 122C5CRRR1 211C5CRRR2 222C5CRRR2 C7CRRR 122C7CRRR1 222C7CRRR1 212C7CRRR1 122C7CRRR2 222C7CRRR2 122C7CRRR/ C9CRRR 211C9CRRR1 R9CCCC 122R9CCCC1 222R9CCCC1 /22R9CCCC1 112R9CCCC1 122R9CCCC2 222R9CCCC2 112R9CCCC2 R9CRRR 122R9CRRR1 C7CRRC 112C7CRRC1 112C7CRRC2 C9CRRC 211C9CRRC1 C7CCCC 211C7CCCC1 222C7CCCC1 122C7CCCC2 C7RCCR 211C7RCCR2 Normal 0.524 (43) 0.085 0.073 0.195 0.146 0.012 0.012 0.049 (4) 0.012 0.024 0.012 0.220 (18) 0.024 0.073 0.000 0.073 0.049 0.012 (1) 0.012 0.073 (6) 0.000 0.000 0.000 0.061 0.012 0.000 0.000 (0) 0.000 0.061 (5) 0.000 0.061 0.012 (1) 0.012 0.037 (3) 0.012 0.024 0.000 0.012 (1) 0.012 Mutant 0.080 (IS) 0.005 0.000 0.020 0.015 0.020 0.020 0.000 0.000 0.000 (0) 0.000 0.000 0.000 Mutations p<10"7 W1310X S1251N G458V, E730X, UC E60X, 622-2A-C, G970R W401X, Y1092X, 3659delC 0.055 (9) p<10"2 0.017 0.005 0.005 0.008 0.010 0.010 0.000 (0) 0.000 1717-1G-A (66.7%) 50.0% of 3272-26A-G 50.0% of 3272-26A-G 1717-1G-A(33.3%) AI507, 4218insT W1282X 0.819 (130) p<10~7 0.466 0.007 0.010 0.007 0.312 0.007 0.007 0.005 (1) 0.005 0.005 (1) 0.005 0.000 0.000 (0) 0.000 0.010 (2) 0.000 0.000 0.010 0.005 (1) 0.005 56.7% of AF508, G542X 1% of AF5O8 A455E 1% of AF5O8 38.1% of AF508, N1303K 1.0% of AF5O8 1% of AF508 1% of AF508 G628R(G-Q/S1235R 2183AA-G 1898+1G-C The proportion of CFTR genes associated with a particular haplotype, and the mutations found to be associated with that haplotype are given. Login to comment

[hide] Detection of 98.5% of the mutations in 200 Belgian... Genomics. 1993 Dec;18(3):693-7. Cuppens H, Marynen P, De Boeck C, Cassiman JJ
Detection of 98.5% of the mutations in 200 Belgian cystic fibrosis alleles by reverse dot-blot and sequencing of the complete coding region and exon/intron junctions of the CFTR gene.
Genomics. 1993 Dec;18(3):693-7., [PMID:7508414]

Abstract [show]
We have previously shown that about 85% of the mutations in 194 Belgian cystic fibrosis alleles could be detected by a reverse dot-blot assay. In the present study, 50 Belgian chromosomes were analyzed for mutations in the cystic fibrosis transmembrane conductance regulator gene by means of direct solid phase automatic sequencing of PCR products of individual exons. Twenty-six disease mutations and 14 polymorphisms were found. Twelve of these mutations and 3 polymorphisms were not described before. With the exception of one mutant allele carrying two mutations, these mutations were the only mutations found in the complete coding region and their exon/intron boundaries. The total sensitivity of mutant CF alleles that could be identified was 98.5%. Given the heterogeneity of these mutations, most of them very rare, CFTR mutation screening still remains rather complex in our population, and population screening, whether desirable or not, does not appear to be technically feasible with the methods currently available.

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43 TABLE 1 Mutations (and Their Frequencies) Identified in This Study Predicted amino Mutation Nucleotide change~ acid change Location Frequencyb Reference E60X G --~ T at 310 (TAGATAGCT) Glu --~ Stop at 60 Malone et al. in (21); this study G --~ A at 482 (GAACACTCT) (8) A --~ C at 622-2 (TTTTCGACT) This study T --~ A at 1139 (AAAAAATTC) This study G --~ A at 1335 (TCTGAGAGG) This study C --~ A at 1496 (TTGGAGGTT) (14) G -~ T at 1505 (GCTGTATCC) (6) Deletion of ATC from 1651 (14); Schwarz et al. (TATC_TTTG) in (21) Deletion of CTT from 1653 145 (13) (TCAT_TGGT) G --~ A at 1717-1 (AATAAGACA) G --~ T at 1756 (TCTTTGAGA) G --~ C at 1898 + 1 (AAAGCTATG) G --~ C at 2014 (TTATCGGAC Deletion of A at 2184; A --~ G at 2183 (AAAAG CAAT) G --~ T at 2320 (TGATTAGCC Deletion of 11 nucleotides from 2721 (TGCT_TAGT) G --~ C at 3040 (AGCACGTAC A --~ G at 3272-26 (TGCAGTGTT) C --~ A at 3408 (TGTAACTGT) Deletion of C at 3659 (CCTA_CAAG) T --~ G at 3837 (TAAGGCCTG G --* A at 3884 (AAGAATACT G --~ A at 3978 (AGTGAAGGA' C --~ G at 4041 (AAAAGTTGG G -~ A at 4061 (CAGTAGAGT Insertion of T after 4218 (CAGTTAAGG) R117H 622-2A --~ C I336K W401X A455E G458V AI507 AF508 1717-1G -~ A G542X 1898+ 1G-~C G628R(G -~ C) 2184delA plus A -~ G at 2183 E730X 2721de111 G970R 3272-26A --~ G Y1092X 3659delc $1235R $1251N W1282X N1303K W1310X 4218insT Exon 3 2 (1.0%) Arg --~ His at 117 Exon 4 c 3' splice signal Intron 4 1 (0.5%) Ile -~ Lys at 336 Exon 7 1 (0.5%) Trp --~ Stop at 401 Exon 8 2 (1.0%) Ala --~ Glu at 455 Exon 9 2 (1.0%) Gly --* Val at 458 Exon 9 1 (0.5%) Deletion of Ile 507 Exon 10 1 (0.5%) Deletion of Phe 508 Exon 10 (72.5%) 3' splice signal Intron 10 5 (2.5%) Gly --* Stop at 542 Exon 11 11 (5.5%) 5' splice signal Intron 12 1 (0.5%) Gly -~ Arg at 628 Exon 13 1 (0.5%) Frameshift Exon 13 2 (1.0%) Glu --~ Stop at 730 Exon 13 1 (0.5%) Frameshift Exon 14a I (0.5%) Gly --~ Arg at 970 Exon 15 1 (0.5%) 5' splice signal? Login to comment
88 The I336K mutation further substantiates the observation that mutations in the first transmembrane regions result in a mild CF phenotype (8, 19). Login to comment
89 Finally, the G970R mutation is located in the second transmembrane region. Login to comment
42 TABLE 1 Mutations (and Their Frequencies) Identified in This Study Predicted amino Mutation Nucleotide change~ acid change Location Frequencyb Reference E60X G --~ T at 310 (TAGATAGCT) Glu --~ Stop at 60 Malone et al. in (21); this study G --~ A at 482 (GAACACTCT) (8) A --~ C at 622-2 (TTTTCGACT) This study T --~ A at 1139 (AAAAAATTC) This study G --~ A at 1335 (TCTGAGAGG) This study C --~ A at 1496 (TTGGAGGTT) (14) G -~ T at 1505 (GCTGTATCC) (6) Deletion of ATC from 1651 (14); Schwarz et al. (TATC_TTTG) in (21) Deletion of CTT from 1653 145 (13) (TCAT_TGGT) G --~ A at 1717-1 (AATAAGACA) G --~ T at 1756 (TCTTTGAGA) G --~ C at 1898 + 1 (AAAGCTATG) G --~ C at 2014 (TTATCGGAC Deletion of A at 2184; A --~ G at 2183 (AAAAG CAAT) G --~ T at 2320 (TGATTAGCC Deletion of 11 nucleotides from 2721 (TGCT_TAGT) G --~ C at 3040 (AGCACGTAC A --~ G at 3272-26 (TGCAGTGTT) C --~ A at 3408 (TGTAACTGT) Deletion of C at 3659 (CCTA_CAAG) T --~ G at 3837 (TAAGGCCTG G --* A at 3884 (AAGAATACT G --~ A at 3978 (AGTGAAGGA' C --~ G at 4041 (AAAAGTTGG G -~ A at 4061 (CAGTAGAGT Insertion of T after 4218 (CAGTTAAGG) R117H 622-2A --~ C I336K W401X A455E G458V AI507 AF508 1717-1G -~ A G542X 1898+ 1G-~C G628R(G -~ C) 2184delA plus A -~ G at 2183 E730X 2721de111 G970R 3272-26A --~ G Y1092X 3659delc $1235R $1251N W1282X N1303K W1310X 4218insT Exon 3 2 (1.0%) Arg --~ His at 117 Exon 4 c 3' splice signal Intron 4 1 (0.5%) Ile -~ Lys at 336 Exon 7 1 (0.5%) Trp --~ Stop at 401 Exon 8 2 (1.0%) Ala --~ Glu at 455 Exon 9 2 (1.0%) Gly --* Val at 458 Exon 9 1 (0.5%) Deletion of Ile 507 Exon 10 1 (0.5%) Deletion of Phe 508 Exon 10 (72.5%) 3' splice signal Intron 10 5 (2.5%) Gly --* Stop at 542 Exon 11 11 (5.5%) 5' splice signal Intron 12 1 (0.5%) Gly -~ Arg at 628 Exon 13 1 (0.5%) Frameshift Exon 13 2 (1.0%) Glu --~ Stop at 730 Exon 13 1 (0.5%) Frameshift Exon 14a I (0.5%) Gly --~ Arg at 970 Exon 15 1 (0.5%) 5' splice signal? Login to comment

[hide] Cystic fibrosis: the 'bicarbonate before chloride'... Curr Biol. 2001 Jun 26;11(12):R463-6. Wine JJ
Cystic fibrosis: the 'bicarbonate before chloride' hypothesis.
Curr Biol. 2001 Jun 26;11(12):R463-6., [PMID:11448786]

Abstract [show]
The specific effects of some mutations that cause cystic fibrosis suggest that reduced HCO(3)(-) transport is the key to understanding cystic fibrosis pathology. But there is a puzzling discrepancy between measures of CFTR-mediated chloride conductance in expression systems and the sweat chloride values of patients.

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52 Ion transport (% WT) 42 41 69 75 >100 >100 98 + 103 100 + + 120 Pancreatic sufficient Pancreatic insufficient Bicarbonate Chloride - intermediate Chloride - high Unknown WT D648V R117H R1070Q H949Y G551S H620Q I148T A1067T G178R G970R S1255P G1244E G551D G1349D 0 0.5 1 1.5 2 2.5 Current Biology ࢞F508 Dispatch R absence of the vas deferens [16]. Login to comment
76 Critical information was provided by Thilo D&#f6;rk (H620Q); R. Moss (R117H & G551D homozygotes); David Kessler, Theresa Grebe and Elizabeth Perkett (D648V); Monica Brooks and contributors to the Cystic Fibrosis Foundation Registry (G178R and G1244E); Aleksey Savov and Luba Kalaydjieva (R1070Q); and Christiane De Boeck and Harry Cuppens (G970R). Login to comment

[hide] [Mucoviscidosis: CFTR mutation-specific therapy: a... Arch Pediatr. 2013 Jan;20(1):63-73. doi: 10.1016/j.arcped.2012.10.018. Epub 2012 Nov 27. Leonard A, Leal T, Lebecque P
[Mucoviscidosis: CFTR mutation-specific therapy: a ray of sunshine in a cloudy sky].
Arch Pediatr. 2013 Jan;20(1):63-73. doi: 10.1016/j.arcped.2012.10.018. Epub 2012 Nov 27., [PMID:23199563]

Abstract [show]
There is a need to find a cure for pulmonary disease in cystic fibrosis (CF), though full benefit of this approach will be restricted to those patients with well-preserved lungs. The most promising route is currently that of a pharmacological mutation-specific approach aiming at correcting the mechanism by which mutations lead to impairment of chloride conductance across respiratory epithelial cells. In the past 14years, 7 candidate drugs (CPX, 4PBA, gentamicin, PTC124, VX-770 or Ivacaftor, VX-809 or Lumacaftor, and Miglustat) have been investigated in CF patients. A postulate of 14 out of the 15 published studies has been that an effective agent had to improve total chloride secretion as assessed in vivo by nasal potential difference measurements. The present review casts a critical look at these studies. Apparent inconsistencies are discussed as well as possible limitations of nasal potential difference measurements as outcome parameters in these trials. Primarily targeting a mutation carried by less than 2% of French CF patients, the 2 Ivacaftor studies could well be a milestone on the long road toward a cure for CF. However, further data on safety and long-term efficacy are obviously needed and the current price of this medication in the US would make it unaffordable for European patients.

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178 De re &#b4;centes donne &#b4;es in vitro sugge `rent que cette me &#b4;dication soit e &#b4;galement efficace sur 9 autres mutations de la me c6;me classe (G178R, S549N, S549R, G551S, G970R, G1244E, S1251N, G1349D) [50,51]. Login to comment

[hide] Managing the underlying cause of cystic fibrosis: ... Paediatr Drugs. 2013 Oct;15(5):393-402. doi: 10.1007/s40272-013-0035-3. Galietta LJ
Managing the underlying cause of cystic fibrosis: a future role for potentiators and correctors.
Paediatr Drugs. 2013 Oct;15(5):393-402. doi: 10.1007/s40272-013-0035-3., [PMID:23757197]

Abstract [show]
Cystic fibrosis (CF), a severe genetic disease, is caused by mutations that alter the structure and function of CFTR, a plasma membrane channel permeable to chloride and bicarbonate. Defective anion transport in CF irreversibly damages the lungs, pancreas, liver, and other organs. CF mutations cause loss of CFTR function in multiple ways. In particular, class 3 mutations such as p.Gly551Asp strongly decrease the time spent by CFTR in the open state (gating defect). Instead, class 2 mutations impair the maturation of CFTR protein and its transport from the endoplasmic reticulum to the plasma membrane (trafficking defect). The deletion of phenylalanine 508 (p.Phe508del), the most frequent mutation among CF patients (70-90 %), destabilizes the CFTR protein, thus causing both a trafficking and a gating defect. These two defects can be overcome with drug-like molecules generically called correctors and potentiators, respectively. The potentiator Kalydeco (also known as Ivacaftor or VX-770), developed by Vertex Pharmaceuticals, has been recently approved by the US FDA and the European Medicines Agency (EMA) for the treatment of CF patients carrying at least one CFTR allele with the p.Gly551Asp mutation (2-5 % of all patients). In contrast, the corrector VX-809, which significantly improves p.Phe508del-CFTR trafficking in vitro, is still under study in clinical trials. Because of multiple defects caused by the p.Phe508del mutation, it is probable that rescue of the mutant protein will require combined treatment with correctors having different mechanisms of action. This review evaluates the status of experimental and clinical research in pharmacotherapy for the CF basic defect.

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108 There are several studies describing the discovery of very effective potentiators, in many cases with nanomolar potency, that can rescue channel activity not only of p.Phe508del, but also of p.Gly551Asp, p.Gly1349Asp, p.Glu193Lys, p.Gly970Arg, p.Asp1152His, and other mutations [51, 52]. Login to comment

[hide] Effect of ivacaftor on CFTR forms with missense mu... J Cyst Fibros. 2014 Jan;13(1):29-36. doi: 10.1016/j.jcf.2013.06.008. Epub 2013 Jul 23. Van Goor F, Yu H, Burton B, Hoffman BJ
Effect of ivacaftor on CFTR forms with missense mutations associated with defects in protein processing or function.
J Cyst Fibros. 2014 Jan;13(1):29-36. doi: 10.1016/j.jcf.2013.06.008. Epub 2013 Jul 23., [PMID:23891399]

Abstract [show]
BACKGROUND: Ivacaftor (KALYDECO, VX-770) is a CFTR potentiator that increased CFTR channel activity and improved lung function in patients age 6 years and older with CF who have the G551D-CFTR gating mutation. The aim of this in vitro study was to evaluate the effect of ivacaftor on mutant CFTR protein forms with defects in protein processing and/or channel function. METHODS: The effect of ivacaftor on CFTR function was tested in electrophysiological studies using a panel of Fischer rat thyroid (FRT) cells expressing 54 missense CFTR mutations that cause defects in the amount or function of CFTR at the cell surface. RESULTS: Ivacaftor potentiated multiple mutant CFTR protein forms that produce functional CFTR at the cell surface. These included mutant CFTR forms with mild defects in CFTR processing or mild defects in CFTR channel conductance. CONCLUSIONS: These in vitro data indicated that ivacaftor is a broad acting CFTR potentiator and could be used to help stratify patients with CF who have different CFTR genotypes for studies investigating the potential clinical benefit of ivacaftor.

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28 These include the most common CFTR gating mutation, G551D, as well as the G178R, S549N, S549R, G551S, G970R, G1244E, S1251N, S1255P, and G1349D mutations [12]. Login to comment

[hide] Ivacaftor: a review of its use in patients with cy... Drugs. 2013 Sep;73(14):1595-604. doi: 10.1007/s40265-013-0115-2. Deeks ED
Ivacaftor: a review of its use in patients with cystic fibrosis.
Drugs. 2013 Sep;73(14):1595-604. doi: 10.1007/s40265-013-0115-2., [PMID:24030637]

Abstract [show]
Ivacaftor (Kalydeco) is a potentiator of the cystic fibrosis transmembrane conductance regulator (CFTR) and is the first drug that treats an underlying cause of cystic fibrosis to be licensed for use. Ivacaftor increases the open probability (i.e. gating) of CFTR channels with the G551D mutation, thus enhancing chloride transport, and is indicated in a number of countries for the treatment of cystic fibrosis in patients aged >/=6 years who carry this mutation. This review focuses on pharmacological, clinical efficacy and tolerability data relevant to the use of ivacaftor in this indication. In two 48-week, double-blind, phase III trials in patients aged >/=12 (STRIVE) or 6-11 (ENVISION) years with cystic fibrosis and the G551D mutation, oral ivacaftor 150 mg every 12 h significantly improved lung function relative to placebo, when used in combination with standard care. Significant improvements in pulmonary exacerbation risk (in STRIVE) as well as bodyweight and some aspects of health-related quality of life (both studies) were also seen with the drug versus placebo. Moreover, the beneficial effects of ivacaftor on parameters such as lung function and bodyweight were maintained over up to 96 weeks of treatment in an ongoing open-label extension of these studies. Ivacaftor was generally well tolerated, with headache, oropharyngeal pain, upper respiratory tract infection and nasal congestion being among the most common adverse events. Thus, ivacaftor expands the current treatment options for patients with cystic fibrosis who have the G551D mutation. Its potential for use in patients with other CFTR mutations is also of interest.

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35 For example, in rodent cells expressing G551D/S, G178R, S549N/R, G970R, G1244E, S1251N, S1255P or G1349D CFTR, ivacaftor increased channel open probability from B5 % of normal at baseline to 30-118 % of normal and increased chloride transport C16- fold (EC50 124-594 nmol/L). Login to comment

[hide] Sinonasal manifestations of cystic fibrosis: a cor... J Cyst Fibros. 2014 Jul;13(4):442-8. doi: 10.1016/j.jcf.2013.10.011. Epub 2013 Nov 5. Berkhout MC, van Rooden CJ, Rijntjes E, Fokkens WJ, el Bouazzaoui LH, Heijerman HG
Sinonasal manifestations of cystic fibrosis: a correlation between genotype and phenotype?
J Cyst Fibros. 2014 Jul;13(4):442-8. doi: 10.1016/j.jcf.2013.10.011. Epub 2013 Nov 5., [PMID:24210900]

Abstract [show]
BACKGROUND: Patients with Cystic Fibrosis are prone to develop sinonasal disease. Studies in genotype-phenotype correlations for sinonasal disease are scarce and inconclusive. METHODS: In this observational study several aspects of sinonasal disease were investigated in 104 adult patients with CF. In each patient a disease specific quality of life questionnaire (RSOM-31), nasal endoscopy and a CT scan of the paranasal sinuses were performed. Patients were divided into two groups, class I-III mutations and class IV-V mutations, based on their CFTR mutations. RESULTS: The prevalence of rhinosinusitis in adult patients with CF was 63% and the prevalence of nasal polyps 25%. Patients with class I-III mutations had significantly smaller frontal sinuses, sphenoid sinuses, more opacification in the sinonasal area and more often osteitis/neoosteogenesis of the maxillary sinus wall compared to patients with class IV and V mutations. CONCLUSION: These data suggest more severe sinonasal disease in patients with class I-III mutations compared to patients with class IV-V mutations.

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163 Genotype Frequency; N (%) Class of mutation F508del/F508del 61 (58.7) I-III F508del/3849 + 10kbC 2 (1.9) IV-V F508del/N1303K 2 (1.9) I-III F508del/R1162X 2 (1.9) I-III F508del/A455E 12 (11.5) IV-V F508del/3272-26A N G 5 (4.8) IV-V F508del/E528X 1 (1.0) I-III F508del/S1251N 3 (2.9) IV-V F508del/R75Q 1 (1.0) IV-V F508del/G542X 2 (1.9) I-III F508del/1717-1G N A 1 (1.0) I-III F508del/Ser489X 1 (1.0) I-III F508del/4382delA 1 (1.0) -a F508del/L1077 1 (1.0) I-III F508del/1813insC 1 (1.0) -b A455E/S1251N 1 (1.0) IV-V A455E/E60X 1 (1.0) IV-V 3272-26A N G/G970R 1 (1.0) IV-V 3272-26A N G/R1162X 1 (1.0) IV-V F508del/UNK 2 (1.9) -c R117H-7T/UNK 1 (1.0) -d UNK/UNK 1 (1.0) -e Total 104 (100.4) One patient with pancreatic sufficiency and diagnosed at 46 years of age (class IV-V). Login to comment

[hide] The relative frequency of CFTR mutation classes in... J Cyst Fibros. 2014 Jul;13(4):403-9. doi: 10.1016/j.jcf.2013.12.003. Epub 2014 Jan 16. De Boeck K, Zolin A, Cuppens H, Olesen HV, Viviani L
The relative frequency of CFTR mutation classes in European patients with cystic fibrosis.
J Cyst Fibros. 2014 Jul;13(4):403-9. doi: 10.1016/j.jcf.2013.12.003. Epub 2014 Jan 16., [PMID:24440181]

Abstract [show]
More than 1900 different mutations in the CFTR gene have been reported. These are grouped into classes according to their effect on the synthesis and/or function of the CFTR protein. CFTR repair therapies that are mutation or mutation class specific are under development. To progress efficiently in the clinical phase of drug development, knowledge of the relative frequency of CFTR mutation classes in different populations is useful. Therefore, we describe the mutation class spectrum in 25,394 subjects with CF from 23 European countries. In 18/23 countries, 80% or more of the patients had at least one class II mutation, explained by F508del being by far the most frequent mutation. Overall 16.4% of European patients had at least one class I mutation but this varied from 3 countries with more than 30% to 4 countries with less than 10% of subjects. Overall only respectively 3.9, 3.3 and 3.0% of European subjects had at least one mutation of classes III, IV and V with again great variability: 14% of Irish patients had at least one class III mutation, 7% of Portuguese patients had at least one class IV mutation, and in 6 countries more than 5% of patients had at least one class V mutation.

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56 Class Type of defect List of mutations attributed to this class Class I Defective protein production Nonsense mutations Large deletions and insertions 1078delT; 1717-1G࢐A; 3659delC; 621+1G࢐T Class II Defective protein processing G85E, F508del, I507del, R560T, N1303K Class III Defective protein regulation ('gating`) G178R, S549N, S549R, G551D, G551S, G970R, G1244E, S1251N, S1255P, G1349D Class IV Defective protein conductance R117H, R334W, R347P Class V Reduced amount of functioning protein 2789+5G࢐A, 3849+10KbC࢐T, A455E Unclassified All other mutations, including those unknown. Login to comment

[hide] Genetics of cystic fibrosis: CFTR mutation classif... Int J Biochem Cell Biol. 2014 Jul;52:94-102. doi: 10.1016/j.biocel.2014.02.023. Epub 2014 Mar 12. Fanen P, Wohlhuter-Haddad A, Hinzpeter A
Genetics of cystic fibrosis: CFTR mutation classifications toward genotype-based CF therapies.
Int J Biochem Cell Biol. 2014 Jul;52:94-102. doi: 10.1016/j.biocel.2014.02.023. Epub 2014 Mar 12., [PMID:24631642]

Abstract [show]
Cystic fibrosis (CF) is an autosomal recessive disease caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene, which encodes an epithelial anion channel. Since the identification of the disease in 1938 and up until 2012, CF patients have been treated exclusively with medications aimed at bettering their respiratory, digestive, inflammatory and infectious symptoms. The identification of the CFTR gene in 1989 gave hopes of rapidly finding a cure for the disease, for which over 1950 mutations have been identified. Since 2012, recent approaches have enabled the identification of small molecules targeting either the CFTR protein directly or its key processing steps, giving rise to novel promising therapeutic tools. This review presents the current CFTR mutation classifications according to their clinical consequences and to their effect on the structure and function of the CFTR channel. How these classifications are essential in the establishment of mutation-targeted therapeutic strategies is then discussed. The future of CFTR-targeted treatment lies in combinatory therapies that will enable CF patients to receive a customized treatment.

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116 Other class III mutations such as the frequent mutations p.Arg560Thr or p.Gly970Arg are listed in Fig. 3 (Seibert et al., 1996). Login to comment

[hide] Personalised medicine in cystic fibrosis is unaffo... Paediatr Respir Rev. 2014 Jun;15 Suppl 1:2-5. doi: 10.1016/j.prrv.2014.04.003. Epub 2014 Apr 13. Balfour-Lynn IM
Personalised medicine in cystic fibrosis is unaffordable.
Paediatr Respir Rev. 2014 Jun;15 Suppl 1:2-5. doi: 10.1016/j.prrv.2014.04.003. Epub 2014 Apr 13., [PMID:24832698]

Abstract [show]
Personalised medicine refers to a tailored approach to treatment of an individual based on molecular analysis of genes, proteins or metabolites, and commonly involves a companion diagnostic test. It usually applies to small subsets of patients, often with rare diseases. In cystic fibrosis (CF), the best example is the CFTR (CF transmembrane conductance regulator) potentiator, ivacaftor, relevant to the 5% of cystic fibrosis patients with the p.Gly551Asp gene mutation. However the cost of personalised medicine is too high, making it unaffordable in the long term for many healthcare systems. Society needs to find a way to make personalised medicine affordable in order to not deny life-changing treatments from patients.

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37 It is currently licensed for use only in those with the p.Gly551Asp mutation; but a further license has been recently approved in the USA for use in other rarer gating mutations (G178R, G551S, S549N, S549R, G970R, G1244E, S1251N, S1255P, or G1349D). Login to comment

[hide] New pharmacological approaches for cystic fibrosis... Pharmacol Ther. 2015 Jan;145:19-34. doi: 10.1016/j.pharmthera.2014.06.005. Epub 2014 Jun 14. Bell SC, De Boeck K, Amaral MD
New pharmacological approaches for cystic fibrosis: promises, progress, pitfalls.
Pharmacol Ther. 2015 Jan;145:19-34. doi: 10.1016/j.pharmthera.2014.06.005. Epub 2014 Jun 14., [PMID:24932877]

Abstract [show]
With the discovery of the CFTR gene in 1989, the search for therapies to improve the basic defects of cystic fibrosis (CF) commenced. Pharmacological manipulation provides the opportunity to enhance CF transmembrane conductance regulator (CFTR) protein synthesis and/or function. CFTR modulators include potentiators to improve channel gating (class III mutations), correctors to improve abnormal CFTR protein folding and trafficking (class II mutations) and stop codon mutation read-through drugs relevant for patients with premature stop codons (most class I mutations). After several successful clinical trials the potentiator, ivacaftor, is now licenced for use in adults and children (>six years), with CF bearing the class III G551D mutation and FDA licence was recently expanded to include 8 additional class III mutations. Alternative approaches for class I and class II mutations are currently being studied. Combination drug treatment with correctors and potentiators appears to be required to restore CFTR function of F508del, the most common CFTR mutation. Alternative therapies such as gene therapy and pharmacological modulation of other ion channels may be advantageous because they are mutation-class independent, however progress is less well advanced. Clinical trials for CFTR modulators have been enthusiastically embraced by patients with CF and health care providers. Whilst novel trial end-points are being evaluated allowing CFTR modulators to be efficiently tested, many challenges related to the complexity of CFTR and the biology of the epithelium still need to be overcome.

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547 Class Type of defect List of mutations attributed to this class Class I Defective protein production Nonsense mutations: G542X, R1162X, RW1282X Deletions and insertions: CFTRdele2,3; 1078delT; 1717-1G ࢐ A; 3659delC; 621+1G N T Class II Defective protein processing G85E, F508del, I507del, R560T, A561E, R1066C, N1303K Class III Defective protein regulation (gating) G178R, S549N, S549R, G551D, G551S, G970R, G1244E, S1251N, S1255P, G1349D Class IV Defective protein conductance R334W, R347P, R117H Class V Reduced amount of functioning protein 2789+5G ࢐ A, 3272-26ANG, 3849+10KbC ࢐ T, A455E Class VI Reduced cell surface stability Rescued F508del, c.120del23 Unclassified All other mutations, including those unknown a F508del-CFTR pocket (at NBD1:ICL4 interface) (Farinha et al., 2013). Login to comment

[hide] CFTR Modulators for the Treatment of Cystic Fibros... P T. 2014 Jul;39(7):500-11. Pettit RS, Fellner C
CFTR Modulators for the Treatment of Cystic Fibrosis.
P T. 2014 Jul;39(7):500-11., [PMID:25083129]

Abstract [show]
Defects in a single gene lead to the defective proteins that cause cystic fibrosis, making the disease an ideal candidate for mutation-targeted therapy. Although ivacaftor is currently the only FDA-approved CFTR modifier, others are in development.

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36 At 48 weeks, 67% of patients in the ivacaftor group had not had a pulmonary exacerbation compared with 41% in the Table 2 Ivacaftor Clinical Trials Reference Design CFTR Mutation Population Treatment Duration Results Ramsey(2011)30 STRIVE: Randomized, double-blind, placebo-controlled G551D Age 12-53 years N = 161 FEV1 40-90% IVA 150 mg b.i.d. or PBO b.i.d. 48 wks ߦ Percent change in FEV1 from baseline to 24 wks (P < 0.001): IVA, 10.4%; PBO, -0.2% ߦ Percent change in FEV1 from baseline to 48 wks compared with PBO (P < 0.001): IVA, 10.5% ߦ Percent of patients pulmonary exacerbation-free at 48 wks: IVA, 67%; PBO, 41% ߦ Change in body weight from baseline to 48 wks: IVA, 3.1 kg; PBO, 0.4 kg ߦ Sweat chloride change from baseline to 48 wks compared with PBO (P < 0.001): IVA, -48.1 mmol/L ߦ Change in CFQ-R respiratory domain from baseline to 48 wks (P < 0.001): IVA, 5.9 pts; PBO, -2.7 pts Davies (2013)29 ENVISION: Randomized, double-blind, placebo-controlled G551D Age 6-11 years N = 52 FEV1 40-105% IVA 150 mg b.i.d. or PBO b.i.d. 48 wks ߦ Absolute change in FEV1 percentage from baseline at 48 wks compared with PBO (P < 0.001): IVA, 10% ߦ Absolute change in FEV1 percentage from baseline at 24 wks (P < 0.001): IVA, 12.6%; PBO, 0.1% ߦ Mean change in sweat chloride from baseline to 48 wks compared with PBO (P < 0.001): IVA, -54.3 mmol/L ߦ Body weight change from baseline to 48 wks compared with PBO (P < 0.001): IVA, 2.8 kg ߦ Absolute CFQ-R change from baseline to 24 wks compared with PBO (P = 0.109): IVA, 6.1 pts McKone (2013)31 PERSIST: Open-label extension G551D Age ࣙ 6 years Patients had completed 48 wks of either ENVISION or STRIVE IVA 150 mg b.i.d. 96 wks (patients received 96 wks or 144 wks of IVA depending on ENVISION or STRIVE randomization) ߦ Absolute change in percent predicted FEV1: &#b0; &#b0; STRIVE (IVA ࢐ IVA) Study start (48 wks of prior treatment): 9.4 &#b1; 8.3 &#b0; &#b0; STRIVE (IVA ࢐ IVA) 144 wks: 9.4 &#b1; 10.8 &#b0; &#b0; STRIVE (PBO ࢐ IVA) Study start: -1.2 &#b1; 7.8 &#b0; &#b0; STRIVE (PBO ࢐ IVA) 96 wks: 9.5 &#b1; 11.2 &#b0; &#b0; ENVISION (IVA ࢐ IVA) Study start (48 wks of prior treatment): 10.2 &#b1; 15.7 &#b0; &#b0; ENVISION (IVA ࢐ IVA) 144 wks: 10.3 &#b1; 12.4 &#b0; &#b0; ENVISION (PBO ࢐ IVA) Study start: -0.6 &#b1; 10.1 &#b0; &#b0; ENVISION (PBO ࢐ IVA) 96 wks: 10.5 &#b1; 11.5 ߦ Absolute change in weight (kg): &#b0; &#b0; STRIVE (IVA ࢐ IVA) Study start (48 wks of prior treatment): 3.4 &#b1; 4.9 &#b0; &#b0; STRIVE (IVA ࢐ IVA) 144 wks: 4.1 &#b1; 7.1 &#b0; &#b0; STRIVE (PBO ࢐ IVA) Study start: 0.3 &#b1; 2.2 &#b0; &#b0; STRIVE (PBO ࢐ IVA) 96 wks: 3 &#b1; 4.2 &#b0; &#b0; ENVISION (IVA ࢐ IVA) Study start (48 wks of prior treatment): 6.1 &#b1; 2.9 &#b0; &#b0; ENVISION (IVA ࢐ IVA) 144 wks: 14.8 &#b1; 5.7 &#b0; &#b0; ENVISION (PBO ࢐ IVA) Study start: 2.9 &#b1; 1.8 &#b0; &#b0; ENVISION (PBO ࢐ IVA) 96 wks: 10.1 &#b1; 4.1 ߦ Absolute change in CFQ-R respiratory domain: &#b0; &#b0; STRIVE (IVA ࢐ IVA) Study start (48 wks of prior treatment): 6.4 &#b1; 16.8 &#b0; &#b0; STRIVE (IVA ࢐ IVA) 144 wks: 6.8 &#b1; 19.6 &#b0; &#b0; STRIVE (PBO ࢐ IVA) Study start: -3.6 &#b1; 14.1 &#b0; &#b0; STRIVE (PBO ࢐ IVA) 96 wks: 9.8 &#b1; 16.2 &#b0; &#b0; ENVISION (IVA ࢐ IVA) Study start (48 wks of prior treatment): 7.4 &#b1; 17.4 &#b0; &#b0; ENVISION (IVA ࢐ IVA) 144 wks: 10.6 &#b1; 18.9 &#b0; &#b0; ENVISION (PBO ࢐ IVA) Study start: 0.8 &#b1; 18.4 &#b0; &#b0; ENVISION (PBO ࢐ IVA) 96 wks: 10.8 &#b1; 12.8 CFTR Modulators for the Treatment of Cystic Fibrosis Table 2 Ivacaftor Clinical Trials Reference Design CFTR Mutation Population Treatment Duration Results Davies (2013)32 Placebo-controlled, double-blind, crossover study G551D Age > 6 years N = 17 FEV1 > 90% LCI > 7.4 Sequence 1: PBO ࢐ WO ࢐ IVA 150 mg b.i.d. Sequence 2: IVA 150 mg b.i.d. ࢐ WO ࢐ PBO 28-day treatment and WO periods ߦ Average change in LCI from baseline compared with PBO (P < 0.0001): IVA, -2.16 (95% CI, -2.88 to -1.44) ߦ Average change in FEV1 from baseline compared with PBO (P = 0.0103): IVA, 8.67 (95% CI, 2.36 to 14.97) ߦ Average change in FEF25-75 from baseline compared with PBO (P = 0.0237): IVA, 16.56 (95% CI, 2.30 to 27.71) Barry (2013)34 Retrospective review G551D Age 20-31 in IVA group N = 21 FEV1 < 40% IVA 150 mg b.i.d. (n = 21); matched controls (n = 35) Median duration, 237 days ߦ Absolute FEV1 change from baseline (P = 0.0075): IVA, 0.125 L; CON, 0.01 L ߦ Percent predicted FEV1 change from baseline (P = 0.0092): IVA, 12.7%, CON, 2.2% ߦ Median weight increase from baseline: IVA, 1.8 kg; CON, 0.1 kg ߦ Median inpatient days per year decreased from 23 days to 0 days in the IVA group (P = 0.001) ߦ Median total intravenous antibiotic days per year decreased from 74 days to 38 days in the IVA group (P = 0.002) De Boeck (2013)37 KONNECTION: Randomized, double-blind, crossover, placebo-controlled Non-G551D gating mutations G178R, G551S, S549N, S549R, G970R, G1244E, S1251N, S1255P, G1349D Age ࣙ 6 years N = 39 FEV1 ࣙ 40% Treatment sequence 1: IVA 150 mg b.i.d. ࢐ WO ࢐ PBO ࢐ open-label Treatment sequence 2: PBO ࢐ WO ࢐ IVA 150 mg b.i.d. ࢐ open-label 8 wks of IVA or PBO; 4-8 wks WO period; 16 wks open label ߦ Absolute change from baseline percent predicted FEV1 (P < 0.0001): IVA, 7.49%; PBO, -3.19% ߦ Absolute change from baseline BMI (P < 0.0001): IVA, 0.68; PBO, 0.02 ߦ Absolute change from baseline in CFQ-R respiratory domain (P = 0.0004): IVA, 8.94 pts; PBO, -0.67 pts ߦ Absolute change from baseline in sweat chloride (mmol/L): IVA, -52.28; PBO, -3.11 Flume (2011)35 Randomized, double-blind, placebo-controlled, parallel group with open-label extension Homozygous F508del Age ࣙ 12 years Part 1: N = 140 Part 2: N = 33 42 patients were eligible for part 2 if change in FEV1 ࣙ 10% or sweat chloride decreased by at least 15 mmol/L at day 15 and week 8 Part 1: IVA 150 mg b.i.d. or PBO 16 wks Part 2: Open label IVA 150 mg b.i.d. 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[hide] Full-open and closed CFTR channels, with lateral t... Cell Mol Life Sci. 2015 Apr;72(7):1377-403. doi: 10.1007/s00018-014-1749-2. Epub 2014 Oct 7. Mornon JP, Hoffmann B, Jonic S, Lehn P, Callebaut I
Full-open and closed CFTR channels, with lateral tunnels from the cytoplasm and an alternative position of the F508 region, as revealed by molecular dynamics.
Cell Mol Life Sci. 2015 Apr;72(7):1377-403. doi: 10.1007/s00018-014-1749-2. Epub 2014 Oct 7., [PMID:25287046]

Abstract [show]
In absence of experimental 3D structures, several homology models, based on ABC exporter 3D structures, have provided significant insights into the molecular mechanisms underlying the function of the cystic fibrosis transmembrane conductance regulator (CFTR) protein, a chloride channel whose defects are associated with cystic fibrosis (CF). Until now, these models, however, did not furnished much insights into the continuous way that ions could follow from the cytosol to the extracellular milieu in the open form of the channel. Here, we have built a refined model of CFTR, based on the outward-facing Sav1866 experimental 3D structure and integrating the evolutionary and structural information available today. Molecular dynamics simulations revealed significant conformational changes, resulting in a full-open channel, accessible from the cytosol through lateral tunnels displayed in the long intracellular loops (ICLs). At the same time, the region of nucleotide-binding domain 1 in contact with one of the ICLs and carrying amino acid F508, the deletion of which is the most common CF-causing mutation, was found to adopt an alternative but stable position. Then, in a second step, this first stable full-open conformation evolved toward another stable state, in which only a limited displacement of the upper part of the transmembrane helices leads to a closure of the channel, in a conformation very close to that adopted by the Atm1 ABC exporter, in an inward-facing conformation. These models, supported by experimental data, provide significant new insights into the CFTR structure-function relationships and into the possible impact of CF-causing mutations.

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355 Second, CF-causing mutations in the ICLs involve residues located at the base of the four-helix bundle assembling the four internal ICL helices (symmetric positions in ICL1 (G178E G178R) and ICL3 (G970R), which cannot be substituted by any other amino acid because of steric hindrance reasons (Fig. 7c; Online Resource 2). Login to comment

[hide] Improving newborn screening for cystic fibrosis us... Genet Med. 2015 Feb 12. doi: 10.1038/gim.2014.209. Baker MW, Atkins AE, Cordovado SK, Hendrix M, Earley MC, Farrell PM
Improving newborn screening for cystic fibrosis using next-generation sequencing technology: a technical feasibility study.
Genet Med. 2015 Feb 12. doi: 10.1038/gim.2014.209., [PMID:25674778]

Abstract [show]
Purpose:Many regions have implemented newborn screening (NBS) for cystic fibrosis (CF) using a limited panel of cystic fibrosis transmembrane regulator (CFTR) mutations after immunoreactive trypsinogen (IRT) analysis. We sought to assess the feasibility of further improving the screening using next-generation sequencing (NGS) technology.Methods:An NGS assay was used to detect 162 CFTR mutations/variants characterized by the CFTR2 project. We used 67 dried blood spots (DBSs) containing 48 distinct CFTR mutations to validate the assay. NGS assay was retrospectively performed on 165 CF screen-positive samples with one CFTR mutation.Results:The NGS assay was successfully performed using DNA isolated from DBSs, and it correctly detected all CFTR mutations in the validation. Among 165 screen-positive infants with one CFTR mutation, no additional disease-causing mutation was identified in 151 samples consistent with normal sweat tests. Five infants had a CF-causing mutation that was not included in this panel, and nine with two CF-causing mutations were identified.Conclusion:The NGS assay was 100% concordant with traditional methods. Retrospective analysis results indicate an IRT/NGS screening algorithm would enable high sensitivity, better specificity and positive predictive value (PPV). This study lays the foundation for prospective studies and for introducing NGS in NBS laboratories.Genet Med advance online publication 12 February 2015Genetics in Medicine (2015); doi:10.1038/gim.2014.209.

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15 Correspondence: Mei W. Baker (mwbaker@wisc.edu) Improving newborn screening for cystic fibrosis using next-generation sequencing technology: a technical feasibility study Mei W. Baker, MD1,2 , Anne E. Atkins, MPH2 , Suzanne K. Cordovado, PhD3 , Miyono Hendrix, MS3 , Marie C. Earley, PhD3 and Philip M. Farrell, MD, PhD1,4 Table 1ߒ CF-causing or varying consequences mutations in the MiSeqDx IUO Cystic Fibrosis System c.1521_1523delCTT (F508del) c.2875delG (3007delG) c.54-5940_273ߙ+ߙ10250del21kb (CFTRdele2,3) c.3909C>G (N1303K) c.3752G>A (S1251N) Mutations that cause CF when combined with another CF-causing mutation c.1624G>T (G542X) c.2988ߙ+ߙ1G>A (3120ߙ+ߙ1G->A) c.3964-78_4242ߙ+ߙ577del (CFTRdele22,23) c.613C>T (P205S) c.1021T>C (S341P) c.948delT (1078delT) c.2988G>A (3120G->A) c.328G>C (D110H) c.200C>T (P67L) c.1397C>A (S466X(C>A)) c.1022_1023insTC (1154insTC) c.2989-1G>A (3121-1G->A) c.3310G>T (E1104X) c.3937C>T (Q1313X) c.1397C>G (S466X(C>G)) c.1081delT (1213delT) c.3140-26A>G (3272-26A->G) c.1753G>T (E585X) c.658C>T (Q220X) c.1466C>A (S489X) c.1116ߙ+ߙ1G>A (1248ߙ+ߙ1G->A) c.3528delC (3659delC) c.178G>T (E60X) c.115C>T (Q39X) c.1475C>T (S492F) c.1127_1128insA (1259insA) c.3659delC (3791delC) c.2464G>T (E822X) c.1477C>T (Q493X) c.1646G>A (S549N) c.1209ߙ+ߙ1G>A (1341ߙ+ߙ1G->A) c.3717ߙ+ߙ12191C>T (3849ߙ+ߙ10kbC->T) c.2491G>T (E831X) c.1573C>T (Q525X) c.1645A>C (S549R) c.1329_1330insAGAT (1461ins4) c.3744delA (3876delA) c.274G>A (E92K) c.1654C>T (Q552X) c.1647T>G (S549R) c.1393-1G>A (1525-1G->A) c.3773_3774insT (3905insT) c.274G>T (E92X) c.2668C>T (Q890X) c.2834C>T (S945L) c.1418delG (1548delG) c.262_263delTT (394delTT) c.3731G>A (G1244E) c.292C>T (Q98X) c.1013C>T (T338I) c.1545_1546delTA (1677delTA) c.3873ߙ+ߙ1G>A (4005ߙ+ߙ1G->A) c.532G>A (G178R) c.3196C>T (R1066C) c.1558G>T (V520F) c.1585-1G>A (1717-1G->A) c.3884_3885insT (4016insT) c.988G>T (G330X) c.3197G>A (R1066H) c.3266G>A (W1089X) c.1585-8G>A (1717-8G->A) c.273ߙ+ߙ1G>A (405ߙ+ߙ1G->A) c.1652G>A (G551D) c.3472C>T (R1158X) c.3611G>A (W1204X) c.1679ߙ+ߙ1.6kbA>G (1811ߙ+ߙ1.6kbA->G) c.274-1G>A (406-1G->A) c.254G>A (G85E) c.3484C>T (R1162X) c.3612G>A (W1204X) c.1680-1G>A (1812-1G->A) c.4077_4080delTGTTinsAA (4209TGTT->AA) c.2908G>C (G970R) c.349C>T (R117C) c.3846G>A (W1282X) c.1766ߙ+ߙ1G>A (1898ߙ+ߙ1G->A) c.4251delA (4382delA) c.595C>T (H199Y) c.1000C>T (R334W) c.1202G>A (W401X) c.1766ߙ+ߙ3A>G (1898ߙ+ߙ 3A->G) c.325_327delTATinsG (457TAT->G) c.1007T>A (I336K) c.1040G>A (R347H) c.1203G>A (W401X) c.2012delT (2143delT) c.442delA (574delA) c.1519_1521delATC (I507del) c.1040G>C (R347P) c.2537G>A (W846X) c.2051_2052delAAinsG (2183AA->G) c.489ߙ+ߙ1G>T (621ߙ+ߙ 1G->T) c.2128A>T (K710X) c.1055G>A (R352Q) c.3276C>A (Y1092X (C>A)) c.2052delA (2184delA) c.531delT (663delT) c.3194T>C (L1065P) c.1657C>T (R553X) c.3276C>G (Y1092X (C>G)) c.2052_2053insA (2184insA) c.579ߙ+ߙ1G>T (711ߙ+ߙ 1G->T) c.3230T>C (L1077P) c.1679G>A (R560K) c.366T>A (Y122X) c.2175_2176insA (2307insA) c.579ߙ+ߙ3A>G (711ߙ+ߙ 3A->G) c.617T>G (L206W) c.1679G>C (R560T) - c.2215delG (2347delG) c.579ߙ+ߙ5G>A (711ߙ+ߙ 5G->A) c.1400T>C (L467P) c.2125C>T (R709X) - c.2453delT (2585delT) c.580-1G>T (712-1G->T) c.2195T>G (L732X) c.223C>T (R75X) - c.2490ߙ+ߙ1G>A (2622ߙ+ߙ1G->A) c.720_741delAGGGAG AATGATGATGAAGTAC (852del22) c.2780T>C (L927P) c.2290C>T (R764X) - c.2583delT (2711delT) c.1364C>A (A455E) c.3302T>A (M1101K) c.2551C>T (R851X) - c.2657ߙ+ߙ5G>A (2789ߙ+ߙ5G->A) c.1675G>A (A559T) c.1A>G (M1V) c.3587C>G (S1196X) - Mutations/variants that were validated in this study are in bold. CF, cystic fibrosis. Table 1ߒ Continued on next page reduce carrier detection and potentially improve the positive predictive value (PPV), the NBS goals of equity and the highest possible sensitivity become more difficult to achieve. Login to comment

[hide] The improvement of the best practice guidelines fo... Eur J Hum Genet. 2015 May 27. doi: 10.1038/ejhg.2015.99. Girardet A, Viart V, Plaza S, Daina G, De Rycke M, Des Georges M, Fiorentino F, Harton G, Ishmukhametova A, Navarro J, Raynal C, Renwick P, Saguet F, Schwarz M, SenGupta S, Tzetis M, Roux AF, Claustres M
The improvement of the best practice guidelines for preimplantation genetic diagnosis of cystic fibrosis: toward an international consensus.
Eur J Hum Genet. 2015 May 27. doi: 10.1038/ejhg.2015.99., [PMID:26014425]

Abstract [show]
Cystic fibrosis (CF) is one of the most common indications for preimplantation genetic diagnosis (PGD) for single gene disorders, giving couples the opportunity to conceive unaffected children without having to consider termination of pregnancy. However, there are no available standardized protocols, so that each center has to develop its own diagnostic strategies and procedures. Furthermore, reproductive decisions are complicated by the diversity of disease-causing variants in the CFTR (cystic fibrosis transmembrane conductance regulator) gene and the complexity of correlations between genotypes and associated phenotypes, so that attitudes and practices toward the risks for future offspring can vary greatly between countries. On behalf of the EuroGentest Network, eighteen experts in PGD and/or molecular diagnosis of CF from seven countries attended a workshop held in Montpellier, France, on 14 December 2011. Building on the best practice guidelines for amplification-based PGD established by ESHRE (European Society of Human Reproduction and Embryology), the goal of this meeting was to formulate specific guidelines for CF-PGD in order to contribute to a better harmonization of practices across Europe. Different topics were covered including variant nomenclature, inclusion criteria, genetic counseling, PGD strategy and reporting of results. The recommendations are summarized here, and updated information on the clinical significance of CFTR variants and associated phenotypes is presented.European Journal of Human Genetics advance online publication, 27 May 2015; doi:10.1038/ejhg.2015.99.

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79 (unknown) Q39X c.115C4T p.Gln39* P67L c.200C4T p.Pro67Leu R75X c.223C4T p.Arg75* 405+1G4A c.273+1G4A 406-1G4A c.274-1G4A E92X c.274G4T p.Glu92* E92K c.274G4A p.Glu92Lys Q98X c.292C4T p.Gln98* 457TAT4G c.325_327delTATinsG p.Tyr109Glyfs*4 D110H c.328G4C p.Asp110His R117C c.349C4T p.Arg117Cys Y122X c.366 T4A p.Tyr122* 574delA c.442delA p.Ile148Leufs*5 444delA c.313delA p.Ile105Serfs*2 663delT c.531delT p.Ile177Metfs*12 G178R c.532G4A p.Gly178Arg 711+3 A4G c.579+3 A4G 711+5G4A c.579+5G4A 712-1G4T c.580-1G4T H199Y c.595C4T p.His199Tyr P205S c.613C4T p.Pro205Ser L206W c.617 T4G p.Leu206Trp Q220X c.658C4T p.Gln220* 852del22 c.720_741delAGGGAGAAT GATGATGAAGTAC p.Gly241Glufs*13 1078delT c.948delT p.Phe316Leufs*12 G330X c.988G4T p.Gly330* Table 1 (Continued ) HGVS nomenclature Legacy name cDNA nucleotide name Protein name R334W c.1000C4T p.Arg334Trp I336K c.1007 T4A p.Ile336Lys T338I c.1013C4T p.Thr338Ile 1154insTC c.1021_1022dupTC p.Phe342Hisfs*28 S341P c.1021 T4C p.Ser341Pro R347H c.1040G4A p.Arg347His 1213delT c.1081delT p.Trp361Glyfs*8 1248+1G4A c.1116+1G4A 1259insA c.1130dupA p.Gln378Alafs*4 W401X(TAG) c.1202G4A p.Trp401* W401X(TGA) c.1203G4A p.Trp401* 1341+1G4A c.1209+1G4A 1461ins4 c.1329_1330insAGAT p.Ile444Argfs*3 1525-1G4A c.1393-1G4A S466X c.1397C4A or c.1397C4G p.Ser466* L467P c.1400 T4C p.Leu467Pro S489X c.1466C4A p.Ser489* S492F c.1475C4T p.Ser492Phe 1677delTA c.1545_1546delTA p.Tyr515* V520F c.1558G4T p.Val520Phe 1717-1G4A c.1585-1G4A 1717-8G4A c.1585-8G4A S549R c.1645 A4C p.Ser549Arg S549N c.1646G4A p.Ser549Asn S549R c.1647 T4G p.Ser549Arg Q552X c.1654C4T p.Gln552* A559T c.1675G4A p.Ala559Thr 1811+1.6kbA4G c.1680-886 A4G 1812-1G4A c.1680-1G4A R560K c.1679G4A p.Arg560Lys E585X c.1753G4T p.Glu585* 1898+3 A4G c.1766+3 A4G 2143delT c.2012delT p.Leu671* 2184insA c.2052_2053insA p.Gln685Thrfs*4 2184delA c.2052delA p.Lys684Asnfs*38 R709X c.2125C4T p.Arg709* K710X c.2128 A4T p.Lys710* 2307insA c.2175dupA p.Glu726Argfs*4 L732X c.2195 T4G p.Leu732* 2347delG c.2215delG p.Val739Tyrfs*16 R764X c.2290C4T p.Arg764* 2585delT c.2453delT p.Leu818Trpfs*3 E822X c.2464G4T p.Glu822* 2622+1G4A c.2490+1G4A E831X c.2491G4T p.Glu831* W846X c.2537G4A p.Trp846* W846X (2670TGG4TGA) c.2538G4A p.Trp846* R851X c.2551C4T p.Arg851* 2711delT c.2583delT p.Phe861Leufs*3 S945L c.2834C4T p.Ser945Leu 2789+2insA c.2657+2_2657+3insA Q890X c.2668C4T p.Gln890* L927P c.2780 T4C p.Leu927Pro 3007delG c.2875delG p.Ala959Hisfs*9 G970R c.2908G4C p.Gly970Arg 3120G4A c.2988G4A function variants that cause CF disease when paired together; (ii) variants that retain residual CFTR function and are compatible with milder phenotypes such as CFTR-RD; (iii) variants with no clinical consequences; and (iv) variants of unproven or uncertain clinical relevance. Login to comment

[hide] New and Emerging Treatments for Cystic Fibrosis. Drugs. 2015 Jul;75(11):1165-75. doi: 10.1007/s40265-015-0424-8. Barry PJ, Jones AM
New and Emerging Treatments for Cystic Fibrosis.
Drugs. 2015 Jul;75(11):1165-75. doi: 10.1007/s40265-015-0424-8., [PMID:26091951]

Abstract [show]
Recently, a significant number of additional key medications have become licensed in Europe for the treatment of patients with cystic fibrosis (CF), including a number of inhaled antibiotics, such as nebulised aztreonam and dry powder versions of colistin and tobramycin for inhalation; dry powder inhaled mannitol, an agent to improve airway hydration and aid airway clearance; and ivacaftor, an oral therapy that directly acts on dysfunctional CFTR to correct the basic defect encountered in CF patients with the G551D CF gene mutation. The marked success of ivacaftor both in clinical trials and in post-licensing evaluation studies in treating patients with G551D and other gating mutations has greatly encouraged the ongoing development of similar therapies that can directly target the underlying cause of CF. Other therapies, including a number of anti-infectives, anti-inflammatories and replacement pancreatic enzymes, are currently undergoing clinical studies. This article reviews those treatments that have been recently licensed for CF and highlights some of the exciting emerging therapies presently under evaluation in clinical trials. In addition, it discusses some of the potential challenges being encountered by research and clinical teams in developing and delivering treatments for this condition.

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58 Improvements were seen for patients with all mutations with the exception of G970R, leading to licensing of ivacaftor for a further eight mutations. Login to comment
59 The finding of G970R as an outlier merits further investigation due to strong pre-clinical data suggesting this mutation would be responsive to CFTR potentiation. Login to comment

[hide] Targeted therapies to improve CFTR function in cys... Genome Med. 2015 Sep 24;7(1):101. doi: 10.1186/s13073-015-0223-6. Brodlie M, Haq IJ, Roberts K, Elborn JS
Targeted therapies to improve CFTR function in cystic fibrosis.
Genome Med. 2015 Sep 24;7(1):101. doi: 10.1186/s13073-015-0223-6., [PMID:26403534]

Abstract [show]
Cystic fibrosis is the most common genetically determined, life-limiting disorder in populations of European ancestry. The genetic basis of cystic fibrosis is well established to be mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene that codes for an apical membrane chloride channel principally expressed by epithelial cells. Conventional approaches to cystic fibrosis care involve a heavy daily burden of supportive treatments to combat lung infection, help clear airway secretions and maintain nutritional status. In 2012, a new era of precision medicine in cystic fibrosis therapeutics began with the licensing of a small molecule, ivacaftor, which successfully targets the underlying defect and improves CFTR function in a subgroup of patients in a genotype-specific manner. Here, we review the three main targeted approaches that have been adopted to improve CFTR function: potentiators, which recover the function of CFTR at the apical surface of epithelial cells that is disrupted in class III and IV genetic mutations; correctors, which improve intracellular processing of CFTR, increasing surface expression, in class II mutations; and production correctors or read-through agents, which promote transcription of CFTR in class I mutations. The further development of such approaches offers great promise for future therapeutic strategies in cystic fibrosis.

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167 Subgroup analysis confirmed these findings for individual genotypes, with the exception of patients with the Gly970Arg mutation, in which there was a substantially less pronounced reduction in sweat chloride levels. Login to comment