ABCMdb

ABCC7 p.Arg334Gln

ClinVar:	c.1000C>T , p.Arg334Trp D , Pathogenic c.1001G>T , p.Arg334Leu ? , not provided c.1001G>A , p.Arg334Gln ? , not provided
CF databases:	c.1000C>T , p.Arg334Trp D , CF-causing ; CFTR1: This mutation has been found in two Spanish CF chromosomes. One of the patients has the [delta]F508 mutation in the other chromosome and the other patient does not. We have not found this mutation on 30 normal chromosomes with the same haplotype, and in 88 CF chromosomes without the [delta]F508, and in 24 with the [delta]F508. The mutation destroys a MapI site and is easily identified by agarose gel electrophoresis after PCR with intron primers. c.1001G>A , p.Arg334Gln (CFTR1) ? , The above mutation was found by DGGE and direct sequencing in Caucasian patients. c.1001G>T , p.Arg334Leu (CFTR1) D , Missense mutation E334L was detected in a German CBAVD patient who is compound heterozygous for the R334L and I336K mutations.
Predicted by SNAP2:	A: D (91%), C: D (95%), D: D (95%), E: D (95%), F: D (95%), G: D (95%), H: D (91%), I: D (95%), K: D (85%), L: D (95%), M: D (95%), N: D (95%), P: D (95%), Q: D (91%), S: D (91%), T: D (95%), V: D (95%), W: D (95%), Y: D (95%),
Predicted by PROVEAN:	A: N, C: D, D: N, E: N, F: D, G: N, H: N, I: D, K: N, L: N, M: N, N: N, P: N, Q: N, S: N, T: N, V: D, W: D, Y: D,

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Publications
[hide] Insight in eukaryotic ABC transporter function by ... FEBS Lett. 2006 Feb 13;580(4):1064-84. Epub 2006 Jan 19. Frelet A, Klein M
Insight in eukaryotic ABC transporter function by mutation analysis.
FEBS Lett. 2006 Feb 13;580(4):1064-84. Epub 2006 Jan 19., 2006-02-13 [PMID:16442101]

Abstract [show]
With regard to structure-function relations of ATP-binding cassette (ABC) transporters several intriguing questions are in the spotlight of active research: Why do functional ABC transporters possess two ATP binding and hydrolysis domains together with two ABC signatures and to what extent are the individual nucleotide-binding domains independent or interacting? Where is the substrate-binding site and how is ATP hydrolysis functionally coupled to the transport process itself? Although much progress has been made in the elucidation of the three-dimensional structures of ABC transporters in the last years by several crystallographic studies including novel models for the nucleotide hydrolysis and translocation catalysis, site-directed mutagenesis as well as the identification of natural mutations is still a major tool to evaluate effects of individual amino acids on the overall function of ABC transporters. Apart from alterations in characteristic sequence such as Walker A, Walker B and the ABC signature other parts of ABC proteins were subject to detailed mutagenesis studies including the substrate-binding site or the regulatory domain of CFTR. In this review, we will give a detailed overview of the mutation analysis reported for selected ABC transporters of the ABCB and ABCC subfamilies, namely HsCFTR/ABCC7, HsSUR/ABCC8,9, HsMRP1/ABCC1, HsMRP2/ABCC2, ScYCF1 and P-glycoprotein (Pgp)/MDR1/ABCB1 and their effects on the function of each protein.

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394 They are positively charged amino acids [171], conserved across species and associated with CF: R334Q/W and R347C/H/L/P. Login to comment

[hide] Complete and rapid scanning of the cystic fibrosis... Hum Genet. 2001 Apr;108(4):290-8. Le Marechal C, Audrezet MP, Quere I, Raguenes O, Langonne S, Ferec C
Complete and rapid scanning of the cystic fibrosis transmembrane conductance regulator (CFTR) gene by denaturing high-performance liquid chromatography (D-HPLC): major implications for genetic counselling.
Hum Genet. 2001 Apr;108(4):290-8., [PMID:11379874]

Abstract [show]
More than 900 mutations and more than 200 different polymorphisms have now been reported in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. Ten years after the cloning of the CFTR gene, the complete scanning of the 27 exons to identify known and novel mutations remains challenging. Rapid accurate identification of mutated alleles is important for prenatal diagnosis, for cascade screening in families at risk of cystic fibrosis (CF) and for understanding the correlation between genotype and phenotype. In this study, we report the successful use of denaturing ion-pair reverse-phase high performance liquid chromatography (D-HPLC) to analyse rapidly the complete coding sequence of the CFTR gene. With 27 pairs of polymerase chain reaction primers, we optimised the temperature conditions required for the analysis of each amplicon and validated thetest conditions on samples from a panel of 1552 CF patients who came from France and other European countries and who had mutations and polymorphisms located in the various melting domains of the gene. D-HPLC identified 415 mutated alleles previously characterised by denaturing gradient gel electrophoresis and DNA sequencing, plus 74 novel mutations reported here. This new technique for screening DNA for sequence variation was extremely accurate (it identified 100% of the CFTR alleles tested so far) and rapid (the complete CFTR gene could be analysed in less than a week). Our approach should reduce the number of untyped CF alleles in populations and thus decrease the residual risk in couples at risk of CF. This technique may be important not only for CF,but also for many other genes with a high frequency of point mutations at a variety of sites.

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114 At 56°C, the profiles of ∆F508 and M470V are identical 295 Table 2 Novel nucleotide changes identified in the CFTR gene and detected by D-HPLC Exon/ intron Mutant name Nucleic acid change Amino acid change Effect on amino acid sequence Patient 1 185+1 G to T G to T at 185+1 Splicing CF patient 2 186 - 13 C to G C to G at 186-13 Silent CF patient 2 211 Del G Deletion of G at 211 Frameshift CF patient 2 237 Ins A Insertion A at 237 Frameshift CF patient 2 296+2 T to C 296+2 T to C Splicing CF patient 3 W 57 X2 G to A at 303 Trp to Stop at 57 (TGG to TGA) Nonsense CF patient 3 306 InsA Insertion of A at 306 Frameshift CF patient 3 306 Ins C Insertion of C at 306 Frameshift CF patient 3 W 79 X G to A at 368 Trp to Stop at 79 (TGG to TAG) Nonsense CF patient 4 A 96 E C to A at 419 Ala to Glu at 96 (GCA to GAA) Missense CF patient 4 L 127 X T to G at 512 Nonsense CF patient 4 541 Del CTCC Deletion of CTCC at 541 Leu to Stop at 127 (TTA to TGA) Frameshift CF patient 5 L 165 S T to C at 626 Leu to Ser at 165 (TTA to TCA) Missense CF patient 5 R 170 C C to T at 640 Arg to Cys at 170 (CGT to TGT) Missense Control 6a L 206 F G to T at 750 Leu to Phe at 206 (TTG to TTT) Missense CF patient 6a A 209 S G to T at 757 Ala to Ser at 209 (GCA toTCA) Missense CF patient 6a A 209 A A to G at 759 Ala to Ala at 209 (GCA to GCG) Silent CF patient 6a C 225 X T to A at 807 Cys to Stop at 225 (TGT to TGA) Nonsense CF patient 6a G 241 R G to A at 852 Gly to Arg at 241 (GGG to AGG) Missense CF patient 6b 905 Del G Deletion of Gat 905 Frameshift CF patient 7 A 309 A C to G at 1059 Ala to Ala at 309 (GCC to GCG) Silent Control 7 V 322 M G to A at 1096 Val to Met at 322 (GTG to ATG) Silent CF patient 7 R 334 Q G to A at 1133 Arg to Gln at 334 (CGG toCAG) Missense Control 7 Q 353 H A to C at 1191 Gln to His at 353 (CAA to CAC) Missense CF patient 7 1248+1 G to C G to C at 1248+1 Splicing CF patient 8 L 383 L G to A at 1281 Leu to Leu at 383 (TTG to TTA) Silent Control 8 W 401 X G to A at 1334 Trp to Stop at 401 (TGG to TAG) Nonsense CF patient 8 E 403 D G to C at 1341 Glu to Asp at 403 (GAG to CAG) Missense CF patient 9 1367 Del C Frameshift CF patient 10 1525 - 2 A to G Deletion of C at 1367 Splicing CF patient 10 G 480 G T to C at 1572 Gly to Gly at 480 (GGT to GGC) Silent CF patient 10 1576 Ins T Insertion of T at 1576 Frameshift CF patient 10 H 484 R A to G at 1583 His to Arg at 484 (CAC to CGC) Missense Neonatal hypertrypsinaemia 10 I506 V A to G at 1648 Ileto Val at 506 (ATC to GTC) Silent Control 11 1717 - 19 T to C T to C at 1717-19 Splicing ? Login to comment

[hide] CFTR: covalent and noncovalent modification sugges... J Gen Physiol. 2001 Oct;118(4):407-31. Smith SS, Liu X, Zhang ZR, Sun F, Kriewall TE, McCarty NA, Dawson DC
CFTR: covalent and noncovalent modification suggests a role for fixed charges in anion conduction.
J Gen Physiol. 2001 Oct;118(4):407-31., [PMID:11585852]

Abstract [show]
The goal of the experiments described here was to explore the possible role of fixed charges in determining the conduction properties of CFTR. We focused on transmembrane segment 6 (TM6) which contains four basic residues (R334, K335, R347, and R352) that would be predicted, on the basis of their positions in the primary structure, to span TM6 from near the extracellular (R334, K335) to near the intracellular (R347, R352) end. Cysteines substituted at positions 334 and 335 were readily accessible to thiol reagents, whereas those at positions 347 and 352 were either not accessible or lacked significant functional consequences when modified. The charge at positions 334 and 335 was an important determinant of CFTR channel function. Charge changes at position 334--brought about by covalent modification of engineered cysteine residues, pH titration of cysteine and histidine residues, and amino acid substitution--produced similar effects on macroscopic conductance and the shape of the I-V plot. The effect of charge changes at position 334 on conduction properties could be described by electrodiffusion or rate-theory models in which the charge on this residue lies in an external vestibule of the pore where it functions to increase the concentration of Cl adjacent to the rate-limiting portion of the conduction path. Covalent modification of R334C CFTR increased single-channel conductance determined in detached patches, but did not alter open probability. The results are consistent with the hypothesis that in wild-type CFTR, R334 occupies a position where its charge can influence the distribution of anions near the mouth of the pore.

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187 MTSES, MTSET, or MTSEA (100 ␮M or 1 mM) were added to the perfusate of oocytes expressing R334A or R334Q CFTR and produced no discernible effect on conductance (unpublished data). Login to comment
313 The conductance of oocytes expressing R334Q CFTR was independent of pH and was not greatly altered by NEM. Login to comment
317 Exposure of oocytes expressing R334Q CFTR to MTSHE produced only small changes in conductance. Login to comment

[hide] Molecular determinants and role of an anion bindin... J Physiol. 2003 Jun 1;549(Pt 2):387-97. Epub 2003 Apr 4. Gong X, Linsdell P
Molecular determinants and role of an anion binding site in the external mouth of the CFTR chloride channel pore.
J Physiol. 2003 Jun 1;549(Pt 2):387-97. Epub 2003 Apr 4., 2003-06-01 [PMID:12679372]

Abstract [show]
Chloride permeation through the cystic fibrosis transmembrane conductance regulator (CFTR) Cl- channel is blocked by highly lyotropic permeant anions which bind tightly within the pore. Here we show that several different substitutions of a positively charged amino acid residue, arginine R334, in the putative outer mouth of the CFTR pore, greatly reduce the block caused by lyotropic Au(CN)2- ions applied to the intracellular side of the channel. Fixed positive charge at this site appears to play a role in Au(CN)2- binding, as judged by multiple substitutions of differently charged amino acid side chains and also by the pH dependence of block conferred by the R334H mutant. However, non-charge-dependent effects also appear to contribute to Au(CN)2- binding. Mutation of R334 also disrupts the apparent electrostatic interaction between intracellular Au(CN)2- ions and extracellular permeant anions, an interaction which normally acts to relieve channel block. All six mutations studied at R334 significantly weakened this interaction, suggesting that arginine possesses a unique ability to coordinate ion-ion interactions at this site in the pore. Our results suggest that lyotropic anions bind tightly to a site in the outer mouth of the CFTR pore that involves interaction with a fixed positive charge. Binding to this site is also involved in coordination of multiple permeant anions within the pore, suggesting that anion binding in the outer mouth of the pore is an important aspect in the normal anion permeation mechanism.

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53 Block of wild-type, R334C-, R334E-, R334H-, R334K-, R334L- and R334Q-CFTR by 100 mM and 1 mM intracellular Au(CN)2 _ are compared in Fig. 4B. Login to comment

[hide] Mutations of the CFTR gene in Turkish patients wit... Hum Reprod. 2004 May;19(5):1094-100. Epub 2004 Apr 7. Dayangac D, Erdem H, Yilmaz E, Sahin A, Sohn C, Ozguc M, Dork T
Mutations of the CFTR gene in Turkish patients with congenital bilateral absence of the vas deferens.
Hum Reprod. 2004 May;19(5):1094-100. Epub 2004 Apr 7., [PMID:15070876]

Abstract [show]
BACKGROUND: Mutations of the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) can cause congenital bilateral absence of the vas deferens (CBAVD) as a primarily genital form of cystic fibrosis. The spectrum and frequency of CFTR mutations in Turkish males with CBAVD is largely unknown. METHODS: We investigated 51 Turkish males who had been diagnosed with CBAVD at the Hacettepe University, Ankara, for the presence of CFTR gene mutations by direct sequencing of the coding region and exon/intron boundaries. RESULTS: We identified 27 different mutations on 72.5% of the investigated alleles. Two-thirds of the patients harboured CFTR gene mutations on both chromosomes. Two predominant mutations, IVS8-5T and D1152H, accounted for more than one-third of the alleles. Five mutations are described for the first time. With one exception, all identified patients harboured at least one mutation of the missense or splicing type. Presently available mutation panels would have uncovered only 7-12% of CFTR alleles in this population cohort. CONCLUSIONS: Although cystic fibrosis is relatively rare in Turkey, CFTR mutations are responsible for the majority of CBAVD in Turkish males. Because of a specific mutation profile, a population-specific panel should be recommended for targeted populations such as CBAVD in Turkey or elsewhere.

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No. Sentence Comment
42 2 (2.0)a This study R74W Exon 3 C®T at 352 Amino acid substitution 1 (1.0) Claustres et al. 1993b 359insT Exon 3 Insertion of T within 360±365 Truncation 1 (1.0) Claustres et al. 1995* A349V Exon 7 C®T at 1178 Amino acid substitution 1 (1.0) Audrezet et al. 1993 R334Q Exon 7 G®A at 1133 Amino acid substitution 1 (1.0) Ferec et al. 1994* T388M Exon 8 C®T at 1295 Amino acid substitution 1 (1.0) Zielenski et al. 1996 IVS8-6T Intron 8 Deletion of T between 1342±12 and 1342±6 Aberrant splicing? Login to comment
47 *The following mutations were previously reported as personal communications to the CF Genetic Analysis Consortium (http://www.genet.sickkids.on.ca): 359insT by Claustres M, Desgeorges M, Romey M-C; R334Q by FeÂrec C, Quere I, Verlingue C, Raguenes O, AudreÂzet M-P, Mercier B; T388M by Zielenski J, Markiewicz D, Tsui L-C, Rawashdeh M, Khateeb M; E831X by FeÂrec C, Quere I, Audrezet MP, Verlingue C, Guillermit H, Mercier B; M952I by Girodon E, Costes B, Cazeneuve C, Ghanem N, Goossens M; R1070W by Macek M Jr, Sedriks S, Kiesewetter S, Cutting GR; D1152H by Highsmith WE Jr, Burch L, Friedman KJ, Wood BM, Spock A, Silverman LM, Knowles MR. Login to comment
72 CFTR genotypes in 51 patients with congenital bilateral absence of the vas deferens Mutation genotypes IVS8-(TG)mTn M470V n (%) Two mutations detected: D1152H/D1152H (TG)11 7T/ (TG)11 7T V/V 5 (9.8) IVS8-5T/IVS8-5T (TG)13 5T/ (TG)13 5T M/M 2 (3.9) (TG)12 5T/ (TG)13 5T M/V 1 (1.9) (TG)12 5T/ (TG)12 5T V/V 1 (1.9) IVS8-5T/D1152H (TG)12 5T/ (TG)11 7T V/V 2 (3.9) IVS8-5T/DF508 (TG)12 5T/ (TG)10 9T M/V 2 (3.9) IVS8-5T/2789+5G®A (TG)12 5T/ (TG)10 7T M/V 2 (3.9) IVS8-5T/365insT (TG)13 5T/ (TG)11 7T M/V 1 (1.9) IVS8-5T/D110H (TG)12 5T/ (TG)11 7T M/V 1 (1.9) IVS8-5T/E585X (TG)12 5T/ (TG)10 7T M/V 1 (1.9) IVS8-5T/2752-15C®G (TG)12 5T/ (TG)11 7T V/V 1 (1.9) IVS8-5T/M952I (TG)12 5T/ (TG)10 7T M/V 1 (1.9) IVS8-5T/3120+1G®A (TG)12 5T/ (TG)11 7T V/V 1 (1.9) D1152H/A349V (TG)10 7T/ (TG)11 7T M/V 1 (1.9) D1152H/2789+5G®A (TG)10 7T/ (TG)11 7T M/V 1 (1.9) D1152H/G1130A (TG)10 7T/ (TG)11 7T M/V 1 (1.9) CFTRdele2(ins186)/ IVS8-6T (TG)13 6T/ (TG)11 7T M/V 1 (1.9) CFTRdele2(ins186)/D110H (TG)11 7T/ (TG)11 7T V/V 1 (1.9) E831X/D110H (TG)11 7T/ (TG)11 7T V/V 1 (1.9) E831X/1677delTA (TG)11 7T/ (TG)11 7T V/V 1 (1.9) R334Q/R347H (TG)11 7T/ (TG)11 7T V/V 1 (1.9) 1767del6/1767del6 (TG)11 7T/ (TG)11 7T V/V 1 (1.9) 3041-15T®G/3041-15T®G (TG)12 7T/ (TG)12 7T M/M 1 (1.9) 3041-13del7/3041-13del7 (TG)10 7T/ (TG)10 7T M/M 1 (1.9) R1070W/3272-26A®G (TG)10 7T/ (TG)11 7T M/V 1 (1.9) I853F/L997F (TG)11 7T/ (TG)10 9T V/V 1 (1.9) One mutation detected: L997F/? Login to comment

[hide] Cystic fibrosis carriers have higher neonatal immu... Am J Med Genet A. 2005 Jun 1;135(2):142-4. Castellani C, Picci L, Scarpa M, Dechecchi MC, Zanolla L, Assael BM, Zacchello F
Cystic fibrosis carriers have higher neonatal immunoreactive trypsinogen values than non-carriers.
Am J Med Genet A. 2005 Jun 1;135(2):142-4., 2005-06-01 [PMID:15832355]

Abstract [show]
Following cystic fibrosis (CF) neonatal screening implementation, a high frequency of heterozygotes has been reported among neonates with elevated immunoreactive trypsinogen (IRT) and normal sweat chloride levels. We studied the relationship between normal IRT values and CF heterozygosity: 10,000 neonates were screened for CF by IRT measurement and tested for 40 CF mutations; the 294 carriers detected were coupled with newborns negative to the same genetic testing, and the two groups' IRT levels compared. Heterozygotes had higher IRT levels than their controls (mean 35.32 vs. 27.58 microg/L, P<0.001). Even within normal trypsinogen range, the probability of being a CF carrier increases with neonatal IRT concentration.

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23 A similar comparison was made between two subgroups including, respectively, 247 carriers of class I, II, and III mutations (in fact the same as in the pancreatic insufficiency mutation group) and 43 carriers of class IV and V mutations [Welsh and Smith, 1993]; mutation R334Q was not included because of difficulties in allocating it to a specific class. Login to comment
40 Distribution and Classification of the Tested Mutations in the Normal IRT Heterozygote Population Under Study Mutations Type of mutation Class of mutation Number of cases F508del Severe II 161 N1303K Severe II 19 G542X Severe I 19 711 þ 5G > A - V 15 R117H Mild IV 13 R1162X Severe I 13 R553X Severe I 11 G85E - IV 8 2183AA > G Severe I 8 1717-1G > A Severe I 8 R334Q Mild - 4 Q552X Severe I 4 W1282X Severe I 3 2789 þ 5G > A Mild V 2 1898 þ 3A > G Mild V 2 T338I Mild IV 1 R709X Severe I 1 R347H Mild IV 1 3849 þ 10KbC > T Mild V 1 Total 294 Other tested mutations: 1078delTn1609delCAn1717-8g/an394delTTn457TAT> Gn541delCn621 þ 1g/tn711 þ 1g/tnA559TnDI507nG551DnR1158XnR334Wn R347PnR352QnS549InS549NnS549Ra/cn2790-2G > An1811 þ 1.2KbA > G; 711þ5G > A and G85E not categorized in type of mutation; R334Q not categorized in class of mutation. Login to comment

[hide] Pharmacological induction of CFTR function in pati... Pediatr Pulmonol. 2005 Sep;40(3):183-96. Kerem E
Pharmacological induction of CFTR function in patients with cystic fibrosis: mutation-specific therapy.
Pediatr Pulmonol. 2005 Sep;40(3):183-96., [PMID:15880796]

Abstract [show]
CFTR mutations cause defects of CFTR protein production and function by different molecular mechanisms. Mutations can be classified according to the mechanisms by which they disrupt CFTR function. This understanding of the different molecular mechanisms of CFTR dysfunction provides the scientific basis for the development of targeted drugs for mutation-specific therapy of cystic fibrosis (CF). Class I mutations are nonsense mutations that result in the presence of a premature stop codon that leads to the production of unstable mRNA, or the release from the ribosome of a short, truncated protein that is not functional. Aminoglycoside antibiotics can suppress premature termination codons by disrupting translational fidelity and allowing the incorporation of an amino acid, thus permitting translation to continue to the normal termination of the transcript. Class II mutations cause impairment of CFTR processing and folding in the Golgi. As a result, the mutant CFTR is retained in the endoplasmic reticulum (ER) and eventually targeted for degradation by the quality control mechanisms. Chemical and molecular chaperones such as sodium-4-phenylbutyrate can stabilize protein structure, and allow it to escape from degradation in the ER and be transported to the cell membrane. Class III mutations disrupt the function of the regulatory domain. CFTR is resistant to phosphorylation or adenosine tri-phosphate (ATP) binding. CFTR activators such as alkylxanthines (CPX) and the flavonoid genistein can overcome affected ATP binding through direct binding to a nucleotide binding fold. In patients carrying class IV mutations, phosphorylation of CFTR results in reduced chloride transport. Increases in the overall cell surface content of these mutants might overcome the relative reduction in conductance. Alternatively, restoring native chloride pore characteristics pharmacologically might be effective. Activators of CFTR at the plasma membrane may function by promoting CFTR phosphorylation, by blocking CFTR dephosphorylation, by interacting directly with CFTR, and/or by modulation of CFTR protein-protein interactions. Class V mutations affect the splicing machinery and generate both aberrantly and correctly spliced transcripts, the levels of which vary among different patients and among different organs of the same patient. Splicing factors that promote exon inclusion or factors that promote exon skipping can promote increases of correctly spliced transcripts, depending on the molecular defect. Inconsistent results were reported regarding the required level of corrected or mutated CFTR that had to be reached in order to achieve normal function.

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58 C-D565G II DF508 D1507 S549R S549I S549N S549R S945D S945L H1054D G1061R L1065P R1066C R1066M L1077P H1085R N1303K G85E III G551D S492F V520F R553G R560T R560S Y569D IV R117H, R117C, R117P, R117L D1152H, L88S, G91R, E92K, Q98R, P205S, L206W, L227R, F311L, G314E, R334W, R334Q, I336K, T338I, L346P, R347C, R347H, R347L, R347P, L927P, R1070W, R1070Q V 3849 þ 10 kb C ! Login to comment

[hide] Gender-sensitive association of CFTR gene mutation... Mol Hum Reprod. 2005 Aug;11(8):607-14. Epub 2005 Aug 26. Morea A, Cameran M, Rebuffi AG, Marzenta D, Marangon O, Picci L, Zacchello F, Scarpa M
Gender-sensitive association of CFTR gene mutations and 5T allele emerging from a large survey on infertility.
Mol Hum Reprod. 2005 Aug;11(8):607-14. Epub 2005 Aug 26., [PMID:16126774]

Abstract [show]
Human infertility in relation to mutations affecting the cystic fibrosis transmembrane regulator (CFTR) gene has been investigated by different authors. The role of additional variants, such as the possible forms of the thymidine allele (5T, 7T and 9T) of the acceptor splice site of intron 8, has in some instances been considered. However, a large-scale analysis of the CFTR gene and number of thymidine residues, alone and in combination, in the two sexes had not yet been addressed. This was the aim of this study. Two groups were compared, a control group of 20,532 subjects being screened for perspective reproduction, and the patient group represented by 1854 idiopathically infertile cases. Analyses involved PCR-based CFTR mutations assessment, reverse dot-blot IVS8-T polymorphism analyses, denaturing gradient gel electrophoresis (DGGE) and DNA sequencing. The expected 5T increase in infertile men was predominantly owing to the 5/9 genotypic class. The intrinsic rate of 5T fluctuated only slightly among groups, but some gender-related differences arose when comparing their association. Infertile men showed a significantly enriched 5T + CFTR mutation co-presence, distributed in the 5/9 and 5/7 classes. In contrast, females, from both the control and the infertile groups, showed a trend towards a pronounced reduction of such association. The statistical significance of the difference between expected and observed double occurrence of 5T + CFTR traits in women suggests, in line with other reports in the literature, a possible survival-hampering effect. Moreover, regardless of the 5T status, CFTR mutations appear not to be involved in female infertility. These results underline the importance of (i) assessing large sample populations and (ii) considering separately the two genders, whose genotypically opposite correlations with these phenomena may otherwise tend to mask each other.

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47 CFTR gene alterations were first scored by PCR and reverse dot blot (Chehab and Wall, 1992), targeted to the detection of the following mutations: ∆F508, G85E, 541∆C, D110H, R117H, 621+1G→T, 711+5G→A, R334W, R334Q, T338I, 1078∆T, R347H, R352Q, ∆I507, 1609∆CA, E527G, 1717-1G→A, 1717-8G→A, G542X, R347P, S549N, S549R A→C, Q552X, R553X, A559T, D579G, Y577F, E585X, 1898+3A→G, 2183AA→G, R709X, 2789+5G→A, 3132∆TG, 3272-26A→G, L1077P, L1065P, R1070Q, R1066H, M1101K, D1152H, R1158X, R1162X, 3849+10KbC→T, G1244E, W1282R, W1282X, N1303K and 4016∇T. Login to comment
79 Concerning instead the mutations found in the male group, besides ∆F508 the following have been found: 2789+5 g/a, 711+5 g/a, D1152H, G85E, N1303K, Q552X, R1158X, R117H, R334Q, R334W and R553X. Login to comment
101 Mutations Women (987) Men (867) N IVS8-T genotype N IVS8-T genotype ∆F508 16 15(7/9); 1(9/9) 26 15(7/9)*; 11(5/9) N1303K 4 4(7/9) 1 7/7 3849+10KbC→T 1 5/7 1 5/7 G542X 2 7/9 1 7/9† 2183AA→G 2 7/7 4 7/7 R553X 2 7/7 0 - R1162X 2 7/7 6 5(7/7)‡; 1(7/9) D1152H 0 - 3 2(7/7); 7/9† 711+5G→A 0 - 3 7/7 1717-8G→A 0 - 1 5/7 1717-1G→A 1 7/7 0 - Y577F 0 - 1 7/7 R117H 1 7/7 1 7/9* 621+3A→G 1 7/9 0 - W1282X 1 7/7 0 - deltaI1507 1 7/7 0 - T3381 1 7/7 1 7/9 R1066H 0 - 1 7/7§ R334Q 0 - 1 7/9 2789+5G→A 1 7/7 2 7/7‡§ Total 36¶ 53¶ records, all these mutations are normally found in trans with respect of 5T. Login to comment

[hide] Direct and indirect effects of mutations at the ou... J Membr Biol. 2007 Apr;216(2-3):129-42. Epub 2007 Aug 3. Zhou JJ, Fatehi M, Linsdell P
Direct and indirect effects of mutations at the outer mouth of the cystic fibrosis transmembrane conductance regulator chloride channel pore.
J Membr Biol. 2007 Apr;216(2-3):129-42. Epub 2007 Aug 3., [PMID:17673962]

Abstract [show]
The cystic fibrosis transmembrane conductance regulator (CFTR) Cl(-) channel pore is thought to contain multiple binding sites for permeant and impermeant anions. Here, we investigate the effects of mutation of different positively charged residues in the pore on current inhibition by impermeant Pt(NO(2)) (4) (2-) and suramin anions. We show that mutations that remove positive charges (K95, R303) influence interactions with intracellular, but not extracellular, Pt(NO(2))(4)(2-) ions, consistent with these residues being situated within the pore inner vestibule. In contrast, mutation of R334, supposedly located in the outer vestibule of the pore, affects block by both extracellular and intracellular Pt(NO(2))(4)(2-). Inhibition by extracellular Pt(NO(2))(4)(2-) requires a positive charge at position 334, consistent with a direct electrostatic interaction resulting in either open channel block or surface charge screening. In contrast, inhibition by intracellular Pt(NO(2))(4)(2-) is weakened in all R334-mutant forms of the channel studied, inconsistent with a direct interaction. Furthermore, mutation of R334 had similar effects on block by intracellular suramin, a large organic molecule that is apparently unable to enter deeply into the channel pore. Mutation of R334 altered interactions between intracellular Pt(NO(2))(4)(2-) and extracellular Cl(-) but not those between intracellular Pt(NO(2))(4)(2-) and extracellular Pt(NO(2))(4)(2-). We propose that while the positive charge of R334 interacts directly with extracellular anions, mutation of this residue also alters interactions with intracellular anions by an indirect mechanism, due to mutation-induced conformational changes in the protein that are propagated some distance from the site of the mutation in the outer mouth of the pore.

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72 Neutralization of a third pore-forming positive charge, in the R334Q mutant, was also associated with significant weakening of the blocking effects of internal Pt(NO2)4 2À (Figs. 1, 2). Login to comment
74 However, unlike K95Q and R303Q, the R334Q mutant weakened Pt(NO2)4 2À block at low, but not high, extracellular ClÀ concentration (Fig. 2). Login to comment
75 This difference likely results from the fact that the R334Q mutation also apparently removes the sensitivity of block to extracellular ClÀ concentration (Figs. 1c, 2). Login to comment
81 Mean of data from three to eight patches. Fitted lines are to equation 1, with the following parameters: wild type 4 mM external ClÀ , Kd(0) = 85.8 lM, zd = À0.201; wild type 154 mM external ClÀ , Kd(0) = 387 lM, zd = À0.344; K95Q 4 mM external ClÀ , Kd(0) = 403 lM, zd = À0.130; K95Q 154 mM external ClÀ , Kd(0) = 978 lM, zd = À0.227; R303Q 4 mM external ClÀ , Kd(0) = 300 lM, zd = À0.096; R303Q 154 mM external ClÀ , Kd(0) = 904 lM, zd = À0.197; R334Q 4 mM external ClÀ , Kd(0) = 286 lM, zd = À0.330; R334Q 154 mM external ClÀ , Kd(0) = 256 lM, zd = À0.307. Login to comment
85 Figure 3 shows the blocking effects of internally applied Pt(NO2)4 2À in six different channel mutants (R334C, R334E, R334H, R334K, R334L, R334Q) under conditions of both low (Fig. 3a) and high (Fig. 3b) extracellular ClÀ concentration. Login to comment
91 With elevated extracellular ClÀ , the Kd(0) was significantly increased only in R334C and R334E; not significantly altered in R334K, R334L and R334Q; and significantly decreased in R334H (Fig. 5b). Login to comment
93 These R334 mutations also exhibited a weakened sensitivity of blocker voltage dependence (quantified as -zd, Fig. 5) to external ClÀ concentration (Fig. 5c), although because of the small magnitude of this effect only R334C, R334H and R334Q reached a level of statistical significance (Fig. 5c). Login to comment
106 Comparison of the mean Kd estimated for suramin (at 0 mV) shows that R334C, R334E, R334K, R334L and R334Q were all associated with weakened suramin block, with only R334H failing to significantly affect suramin block (Fig. 7). Login to comment
110 As shown in Figure 8, although block by internal Pt(NO2)4 2À is significantly weakened in R334Q, this blocking effect is still sensitive to the presence of Pt(NO2)4 2À ions in the extracellular solution. Login to comment
111 In wild type, addition of 8 mM Pt(NO2)4 2À to the extracellular solution increased mean Kd(0) for intracellular Pt(NO2)4 2À approximately 2.7-fold without significantly altering -zd, while in R334Q this concentration of extracellular Pt(NO2)4 2À increased mean Kd(0) 2.5-fold, again with no significant change in -zd (Fig. 8c). Login to comment
112 Thus, the R334Q mutation practically abolishes the dependence of intracellular Pt(NO2)4 2À block on external ClÀ (Figs. 1c, 2, 5c) without significantly altering its dependence on external Pt(NO2)4 2À (Fig. 8). Login to comment
129 Mean of data from three to eight patches. Fitted lines are to equation 1 as described in Figure 1 for wild type and R334Q and with the following parameters for other channel variants: R334C 4 mM external ClÀ , Kd(0) = 1362 lM, zd = À0.295; R334C 154 mM external ClÀ , Kd(0) = 836 lM, zd = À0.219; R334E 4 mM external ClÀ , Kd(0) = 759 lM, zd = À0.376; R334E 154 mM external ClÀ , Kd(0) = 564 lM, zd = À0.173; R334H 4 mM external ClÀ , Kd(0) = 140 lM, zd = À0.166; R334H 154 mM external ClÀ , Kd(0) = 119 lM, zd = À0.149; R334K 4 mM external ClÀ , Kd(0) = 143 lM, zd = À0.314; R334K 154 mM external ClÀ , Kd(0) = 317 lM, zd = À0.374; R334L 4 mM external ClÀ , Kd(0) = 176 lM, zd = À0.258; R334L 154 mM external ClÀ , Kd(0) = 284 lM, zd = À0.366 extracellular Pt(NO2)4 2À by normalizing current amplitude at the hyperpolarized extreme of the voltage range studied, -80 mV (Fig. 10b). Login to comment
159 These plots represent mean data from four to seven patches. Fitted lines are to equation 1 with the following parameters: wild type, Kd(0) = 2.51 lM, zd = À0.042; R334C, Kd(0) = 18.5 lM, zd = À0.056; R334E, Kd(0) = 25.0 lM, zd = À0.107; R334H, Kd(0) = 3.10 lM, zd = À0.085; R334K, Kd(0) = 6.31 lM, zd = À0.232; R334L, Kd(0) = 4.08 lM, zd = À0.061; R334Q, Kd(0) = 6.64 lM, zd = À0.239 with our previous suggestion that intracellular Au(CN)2 À blocks the channel by interacting directly with R334, several reasons prompt us to suggest that Pt(NO2)4 2À does not interact directly with the arginine side chain at this position. Login to comment
171 a Example leak-subtracted macroscopic current-voltage relationships recorded with 8 mM K2Pt(NO2)4 2À present in the extracellular solution for wild type (left) and R334Q (right), recorded before (control) and after (+ Pt[NO2]4) addition of 300 lM K2Pt(NO2)4 to the intracellular solution. Login to comment
173 Mean of data from three to eight patches. Fitted lines are to equation 1 with the following parameters: wild type (), Kd(0) = 85.8 lM, -zd = 0.201; wild type (d), Kd(0) = 205 lM, - zd = 0.248; R334Q (), Kd(0) = 286 lM, -zd = 0.330; R334Q (d), Kd(0) = 704 lM, -zd = 0.401. c Mean Kd(0) and -zd calculated under these conditions, without extracellular Pt(NO2)4 2À (white bars) and with 8 mM Pt(NO2)4 2À (black bars). Login to comment
214 Furthermore, we suggest that external Pt(NO2)4 2À and external ClÀ destabilize the binding of internal blockers by different mechanisms since the effects of ClÀ , but not Pt(NO2)4 2À , are lost in R334Q. Login to comment
228 ), R334E (5), R334H (j), R334K (), R334L (h), R334Q (u); c wild type (d), K95Q (m), R303Q (Å). Login to comment

[hide] A 10-year large-scale cystic fibrosis carrier scre... J Cyst Fibros. 2010 Jan;9(1):29-35. Epub 2009 Nov 7. Picci L, Cameran M, Marangon O, Marzenta D, Ferrari S, Frigo AC, Scarpa M
A 10-year large-scale cystic fibrosis carrier screening in the Italian population.
J Cyst Fibros. 2010 Jan;9(1):29-35. Epub 2009 Nov 7., [PMID:19897426]

Abstract [show]
BACKGROUND: Cystic Fibrosis (CF) is one of the most common autosomal recessive genetic disorders, with the majority of patients born to couples unaware of their carrier status. Carrier screenings might help reducing the incidence of CF. METHODS: We used a semi-automated reverse-dot blot assay identifying the 47 most common CFTR gene mutations followed by DGGE/dHPLC analysis. RESULTS: Results of a 10-year (1996-2006) CF carrier screening on 57,999 individuals with no prior family history of CF are reported. Of these, 25,104 were couples and 7791 singles, with 77.9% from the Italian Veneto region. CFTR mutations were found in 1879 carriers (frequency 1/31), with DeltaF508 being the most common (42.6%). Subjects undergoing medically assisted reproduction (MAR) had significantly (p<0.0001) higher CF carrier frequency (1/22 vs 1/32) compared to non-MAR subjects. CONCLUSIONS: If coupled to counselling programmes, CF carrier screening tests might help reducing the CF incidence.

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48 Forty-seven different CFTR mutations/gene alterations were chosen and analysed: ΔF508, G85E, 541delC, D110H, R117H, 621+1G→T, 711+5G→A, R334W, R334Q, T338I, R347H, R347P, R352Q, S466X, ΔI507, E527G, 1717-1G→A, 1717-8G→A, G542X, S549N, S549R A→C, G551D, Q552X, R553X, D579G, 1874insT, E585X, 1898+3A→G, 2183AA→G, 2184delA, R709X, 2789+5G→A, 3132delTG, 3199del6, 3272-26A→G, L1077P, L1065P, R1066H, M1101K, D1152H, R1158X, R1162X, 3849+10KbC→T, G1244E, W1282X, N1303K and 4016insT. Login to comment
97 CF mutation General adult population MAR population n=1879 n=236 ΔF508 42.6 45.7 2183AA→G 5.9 5.9 R1162X 5.7 8.2 N1303K 5.4 5.9 G542X 4.2 3.7 D1152H 3.9 5.0 R553X 3.7 3.1 R117H 3.3 1.8 711+5G→A 2.8 4.1 Q552X 2.8 0.4 2789+5G→A 2.2 3.1 1717-1G→A 2.6 2.8 E527G 2.4 - G85E 2.4 0.9 R334Q 0.9 0.4 W1282X 0.7 0.9 R334W 0.6 - 1898+3A→G 0.5 0.4 R1158X 0.4 - R1066H 0.4 0.4 T338I 0.4 1.8 3849+10Kb C→T 0.4 1.3 3272-26 A→G - 0.9 3132delTG - 0.9 3659 del C - 0.4 4016 ins T - 0.4 1717-8G→A - 0.4 R347H - 0.4 ΔI507 - 0.4 R1070Q - 0.4 Other (16) 5.4 - Table 2a List of CFTR compound heterozygotes in the adult general population. Mutation Health status Disorder Gender Age (years) Notes and refs ΔF508/A238V Infertile CBAVD M 36 (A) ΔF508/R352W Infertile CBAVD M 45 (A) R553X/R334Q M 38 ΔF508/R347H M 53 [17] S42F/D372E (1251T→G) M 39 (A) (B) ΔF508/D110H Infertile M 38 ΔF508/L1414S (4373T→C) Infertile CBAVD M 44 (A) (B) ΔF508/V201M, D1270N & R74W Infertile CBAVD M 44 (A) [18,19] 2183AA→G/L206W Infertile CBAVD M 40 (A) 711+5G→A/ L206W Infertile CBAVD M 40 (A) Table 2b List of CFTR compound heterozygotes in the population enrolled for medically assisted reproduction. Login to comment

[hide] Association of cystic fibrosis genetic modifiers w... Fertil Steril. 2010 Nov;94(6):2122-7. Epub 2010 Jan 25. Havasi V, Rowe SM, Kolettis PN, Dayangac D, Sahin A, Grangeia A, Carvalho F, Barros A, Sousa M, Bassas L, Casals T, Sorscher EJ
Association of cystic fibrosis genetic modifiers with congenital bilateral absence of the vas deferens.
Fertil Steril. 2010 Nov;94(6):2122-7. Epub 2010 Jan 25., [PMID:20100616]

Abstract [show]
OBJECTIVE: To investigate whether genetic modifiers of cystic fibrosis (CF) lung disease also predispose to congenital bilateral absence of the vas deferens (CBAVD) in association with cystic fibrosis transmembrane conductance regulator (CFTR) mutations. We tested the hypothesis that polymorphisms of transforming growth factor (TGF)-beta1 (rs 1982073, rs 1800471) and endothelin receptor type A (EDNRA) (rs 5335, rs 1801708) are associated with the CBAVD phenotype. DESIGN: Genotyping of subjects with clinical CBAVD. SETTING: Outpatient and hospital-based clinical evaluation. PATIENT(S): DNA samples from 80 subjects with CBAVD and 51 healthy male controls from various regions of Europe. This is one of the largest genetic studies of this disease to date. INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): Genotype analysis. RESULT(S): For single nucleotide polymorphism (SNP) rs 5335, we found increased frequency of the CC genotype among subjects with CBAVD. The difference was significant among Turkish patients versus controls (45.2% vs. 19.4%), and between all cases versus controls (36% vs. 15.7%). No associations between CBAVD penetrance and polymorphisms rs 1982073, rs 1800471, or rs 1801708 were observed. CONCLUSION(S): Our findings indicate that endothelin receptor type A polymorphism rs 5335 may be associated with CBAVD penetrance. To our knowledge, this is the first study to investigate genetic modifiers relevant to CBAVD.

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68 Portuguese CFTR alleles Spanish CFTR alleles Turkish CFTR alleles 5T 22 F508del 11 5T 20 F508del 14 5T 9 D1152H 14 R334W 5 D443Ya 3 D110H 3 R117H 3 G576Aa 3 F508del 2 S1235R 3 R668Ca 3 3041-11del7 2 N1303K 2 G542X 2 1767del6 2 P205S 2 R117H 2 2789þ5G>A 2 D614G 2 V232D 2 CFTRdele2(ins186) 2 G542X 1 L997F 1 3120þ1G>A 1 L206W 1 H609R 1 G1130A 1 V562I 1 N1303H 1 M952I 1 I507del 1 L206W 1 365insT 1 3272-26A>G 1 3272-26A/G 1 E585X 1 2789þ5G>A 1 L15P 1 2752-15C>G 1 G576Aa 1 R347H 1 R334Q 1 R668Ca 1 2689insG 1 R347H 1 CFTRdele2,3 1 R1070W 1 E831X 1 L1227S 1 I 1027T 1 R1070W 1 E831X 1 3272-26A>G 1 L997F 1 I853F 1 A349V 1 6T 1 Note: CFTR ¼ cystic fibrosis transmembrane conductance regulator. Login to comment

[hide] Identification of the second CFTR mutation in pati... Asian J Androl. 2010 Nov;12(6):819-26. Epub 2010 Jul 26. Giuliani R, Antonucci I, Torrente I, Grammatico P, Palka G, Stuppia L
Identification of the second CFTR mutation in patients with congenital bilateral absence of vas deferens undergoing ART protocols.
Asian J Androl. 2010 Nov;12(6):819-26. Epub 2010 Jul 26., [PMID:20657600]

Abstract [show]
Congenital bilateral absence of vas deferens (CBAVD) is a manifestation of the mildest form of cystic fibrosis (CF) and is characterized by obstructive azoospermia in otherwise healthy patients. Owing to the availability of assisted reproductive technology, CBAVD patients can father children. These fathers are at risk of transmitting a mutated allele of the CF transmembrane conductance regulator (CFTR) gene, responsible for CF, to their offspring. The identification of mutations in both CFTR alleles in CBAVD patients is a crucial requirement for calculating the risk of producing a child with full-blown CF if the female partner is a healthy CF carrier. However, in the majority of CBAVD patients, conventional mutation screening is not able to detect mutations in both CFTR alleles, and this difficulty hampers the execution of correct genetic counselling. To obtain information about the most represented CFTR mutations in CBAVD patients, we analysed 23 CBAVD patients, 15 of whom had a single CFTR mutation after screening for 36 mutations and the 5T allele. The search for the second CFTR mutation in these cases was performed by using a triplex approach: (i) first, a reverse dot-blot analysis was performed to detect mutations with regional impact; (ii) next, multiple ligation-dependent probe amplification assays were conducted to search for large rearrangements; and (iii) finally, denaturing high-performance liquid chromatography was used to search for point mutations in the entire coding region. Using these approaches, the second CFTR mutation was detected in six patients, which increased the final detection rate to 60.8%.

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58 INNO-LiPA CFTR19 INNO-LiPA CFTR17 INNO-LiPA CFTR Italian regional [delta]F508 621+1G>T 1259insA G542X 3849+10kbC>T 4016insT N1303K 2183AA>G 4382delA W1282X 394delTT 852del22 G551D 2789+5G> A R1162X D579G 1717-1G>A 3659delC G1244E R553X R117H G1349D CFTRdele2,3 (21 kb) R334W I502T [delta]I507 R347P L1065P 711+1G>T G85E R1158X 3272-26A>G 3905insT 1078delT T338I R560T A455E S549R(A>C) 1898+1G>A S1251N 2143delA 711+5G>A 991del5 I148T E60X D1152H 3199del6 3120+1G>A 2184delA 1898+3A>G, R1070Q Q552X Poli-T tract variations R1066H R347H 621+3A>G R334Q E217G Abbreviation: CFTR, cystic fibrosis transmembrane conductance regulator. 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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98 These residues are conserved across spe- because I0 blocks the pore, it appears that I0 is less per- cies, and two are the site of mutations associated with meable under some conditions, including the whole cell CF: R334Q/W and R347C/H/L/P (142). Login to comment

[hide] Clinical outcome of preimplantation genetic diagno... Eur J Hum Genet. 2007 Jul;15(7):752-8. Epub 2007 Apr 18. Keymolen K, Goossens V, De Rycke M, Sermon K, Boelaert K, Bonduelle M, Van Steirteghem A, Liebaers I
Clinical outcome of preimplantation genetic diagnosis for cystic fibrosis: the Brussels' experience.
Eur J Hum Genet. 2007 Jul;15(7):752-8. Epub 2007 Apr 18., [PMID:17440499]

Abstract [show]
Preimplantation genetic diagnosis is an alternative for prenatal diagnosis that makes it possible to perform the diagnosis of a chromosomal or monogenic disorder at the preimplantation embryo level. Cystic fibrosis is one of the monogenic diseases for which PGD can be performed. In this study, we looked at the requests and PGD cycles for this particular disorder over an 11-year period. Sixty-eight percent of the requests eventually led to at least one complete PGD cycle. In 80% of the cycles, an embryo transfer was performed and an ongoing pregnancy was obtained in 22.2% of the cycles with oocyte retrieval. After embryo transfer, a couple had 27.8% chance of giving birth to a liveborn child. No misdiagnosis was recorded. The rate of perinatal deaths/stillborn children was relatively high, but no excess of major congenital anomalies was observed in the surviving children.

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66 Table 1 Assessment of CF risk Couples with PGD (n ¼ 47) Couples without PGD (n ¼ 22) All couples (n ¼ 69)(%) CF risk assessment Affected child or foetus 23 14 37 (53.6) CBAVD (without other CF complaints) 7 3 10 (14.5) During fertility work-up (not CBAVD) 10 10 (14.5) Positive family history 3 2 5 (7.2) CF patient (with CBAVD in males) 4 4 (5.8) Unknown 2 2 (2.9) Preconceptual screening 1 1 (1.4) Table 2 Reasons for choosing PGD Couples with PGD (n ¼ 47) Couples without PGD (n ¼ 22) All couples (n ¼ 69) Reason for choosing/informing about PGD Fertility problems 24 7 31 (44.9%) Objection to abortion 15 2 17 (24.6%) History of termination of pregnancy 8 1 9 (13%) Unknown 11 11 (15.9%) Other 1 1 (1.4%) Table 3 Genotypes of the couples with PGD cycles Female partner Male partner Number of couples with this genotype p.F508del/- p.F508del/- 17 p.F508del/- p.R117H/- (7T/9T) 1 p.2789+5G4A/- p.D110H/p.D110H 1 p.G542X/- p.F508del/- 1 p.R334Q/- p.F508del/- 1 p.R553X/- p.F508del/- 2 p.1717-1G4A p.2183AA4G/5T 1 p.F508del/- p.F508del/? Login to comment

[hide] Pseudohalide anions reveal a novel extracellular s... Br J Pharmacol. 2012 Nov;167(5):1062-75. doi: 10.1111/j.1476-5381.2012.02041.x. Li MS, Cowley EA, Linsdell P
Pseudohalide anions reveal a novel extracellular site for potentiators to increase CFTR function.
Br J Pharmacol. 2012 Nov;167(5):1062-75. doi: 10.1111/j.1476-5381.2012.02041.x., [PMID:22612315]

Abstract [show]
BACKGROUND AND PURPOSE There is great interest in the development of potentiator drugs to increase the activity of the cystic fibrosis transmembrane conductance regulator (CFTR) in cystic fibrosis. We tested the ability of several anions to potentiate CFTR activity by a novel mechanism. EXPERIMENTAL APPROACH Patch clamp recordings were used to investigate the ability of extracellular pseudohalide anions (Co(CN)(6) (3-) , Co(NO(2) )(6) (3-) , Fe(CN)(6) (3-) , IrCl(6) (3-) , Fe(CN)(6) (4-) ) to increase the macroscopic conductance of mutant CFTR in intact cells via interactions with cytoplasmic blocking anions. Mutagenesis of CFTR was used to identify a possible molecular mechanism of action. Transepithelial short-circuit current recordings from human airway epithelial cells were used to determine effects on net anion secretion. KEY RESULTS Extracellular pseudohalide anions were able to increase CFTR conductance in intact cells, as well as increase anion secretion in airway epithelial cells. This effect appears to reflect the interaction of these substances with a site on the extracellular face of the CFTR protein. CONCLUSIONS AND IMPLICATIONS Our results identify pseudohalide anions as increasing CFTR function by a previously undescribed molecular mechanism that involves an interaction with an extracellular site on the CFTR protein. Future drugs could utilize this mechanism to increase CFTR activity in cystic fibrosis, possibly in conjunction with known intracellularly-active potentiators.

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37 In some experiments, additional mutations (R334Q, K892Q, R899Q) were introduced into this background using the QuikChange site-directed mutagenesis system. Login to comment
104 Examples of the macroscopic I-V relationships for R334Q, K892Q, R899Q and K892Q/R899Q (all in an E1371Q background) are shown in Figure 5A. Login to comment
105 Apparent block in intact cells was weak in R334Q and was not significantly weakened further by inclusion of 10 mM Co(CN)6 3- (Figure 5D) or Co(NO2)6 3- (Figure 5E) in the pipette solution. Login to comment
113 Each of these mutants (R334Q, K892Q, R899Q, K892Q/R899Q) also abolished the sensitivity of current inhibition in intact cells to extracellular Cl- ions (Figure 6). Login to comment
207 This suggestion of a non-pore-mediated effect is further strengthened by the effects of mutations that remove positive charges from the extracellular face of the CFTR protein. Thus the R334Q mutant, which neutralizes a pore lining positive charge that is known to attract extracellular anions into the outer mouth of the pore (Smith et al., 2001; Gong and Linsdell, 2003c; Zhou et al., 2007), did affect the ability of Co(CN)6 3- and Co(NO2)6 3- to weaken apparent channel block in intact cells (Figures 5, 7). Login to comment
208 However, this apparent lack of pseudohalide sensitivity in R334Q appears to reflect weak cytoplasmic block under control conditions rather than a specific loss of external anion sensitivity of block (Figure 7). Login to comment
209 This interpretation is consistent with the R334Q mutation itself affecting cytoplasmic blocker interactions with CFTR (Zhou et al., 2007). Login to comment

[hide] Maximization of the rate of chloride conduction in... Arch Biochem Biophys. 2004 Jun 1;426(1):78-82. Gong X, Linsdell P
Maximization of the rate of chloride conduction in the CFTR channel pore by ion-ion interactions.
Arch Biochem Biophys. 2004 Jun 1;426(1):78-82., [PMID:15130785]

Abstract [show]
Multi-ion pore behaviour has been identified in many Cl(-) channel types but its biophysical significance is uncertain. Here, we show that mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) Cl(-) channel that disrupt anion-anion interactions within the pore are associated with drastically reduced single channel conductance. These results are consistent with models suggesting that rapid Cl(-) permeation in CFTR results from repulsive ion-ion interactions between Cl(-) ions bound concurrently inside the pore. Naturally occurring mutations that disrupt these interactions can result in cystic fibrosis.

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35 Results and discussion Previously we characterized the properties of six different R334 mutants (R334C, R334E, R334H, R334K, R334L, and R334Q) [19]. Login to comment
66 R334Q, and (,) R334W. Login to comment
98 Interestingly, three of these mutations-R334L, R334Q, and R334W-have been identified in cystic fibrosis patients [29]. Login to comment

[hide] Evidence that extracellular anions interact with a... Can J Physiol Pharmacol. 2009 May;87(5):387-95. doi: 10.1139/y09-023. Zhou JJ, Linsdell P
Evidence that extracellular anions interact with a site outside the CFTR chloride channel pore to modify channel properties.
Can J Physiol Pharmacol. 2009 May;87(5):387-95. doi: 10.1139/y09-023., [PMID:19448737]

Abstract [show]
Extracellular anions enter into the pore of the cystic fibrosis transmembrane conductance regulator (CFTR) Cl- channel, interacting with binding sites on the pore walls and with other anions inside the pore. There is increasing evidence that extracellular anions may also interact with sites away from the channel pore to influence channel properties. We have used site-directed mutagenesis and patch-clamp recording to identify residues that influence interactions with external anions. Anion interactions were assessed by the ability of extracellular Pt(NO2)42- ions to weaken the pore-blocking effect of intracellular Pt(NO2)42- ions, a long-range ion-ion interaction that does not appear to reflect ion interactions inside the pore. We found that mutations that remove positive charges in the 4th extracellular loop of CFTR (K892Q and R899Q) significantly alter the interaction between extracellular and intracellular Pt(NO2)42- ions. These mutations do not affect unitary Cl- conductance or block of single-channel currents by extracellular Pt(NO2)42- ions, however, suggesting that the mutated residues are not in the channel pore region. These results suggest that extracellular anions can regulate CFTR pore properties by binding to a site outside the pore region, probably by a long-range conformational change. Our findings also point to a novel function of the long 4th extracellular loop of the CFTR protein in sensing and (or) responding to anions in the extracellular solution.

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38 Consistent with this distinction, we previously showed that the R334Q mutation at the outer mouth of the pore disrupted interactions between external Cl- and internal Pt(NO2)4 2-, without affecting interactions between external Pt(NO2)4 2- and internal Pt(NO2)4 2- (Zhou et al. 2007). Login to comment
67 Similar weakening of block by internal Pt(NO2)4 2-was also observed in K114C, K329A, K335A, and R1128Q (Fig. 2), as well as R334Q (Zhou et al. 2007). Login to comment
127 The effects of external Pt(NO2)4 2are sensitive to mutations away from the pore (K892Q, R899Q) but not deep within the pore (K335A, R334Q), which would be expected to alter ion-ion interactions in the pore. Login to comment

[hide] Understanding how cystic fibrosis mutations disrup... Int J Biochem Cell Biol. 2014 Jul;52:47-57. doi: 10.1016/j.biocel.2014.04.001. Epub 2014 Apr 13. Wang Y, Wrennall JA, Cai Z, Li H, Sheppard DN
Understanding how cystic fibrosis mutations disrupt CFTR function: from single molecules to animal models.
Int J Biochem Cell Biol. 2014 Jul;52:47-57. doi: 10.1016/j.biocel.2014.04.001. Epub 2014 Apr 13., [PMID:24727426]

Abstract [show]
Defective epithelial ion transport is the hallmark of the life-limiting genetic disease cystic fibrosis (CF). This abnormality is caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR), the ATP-binding cassette transporter that functions as a ligand-gated anion channel. Since the identification of the CFTR gene, almost 2000 disease-causing mutations associated with a spectrum of clinical phenotypes have been reported, but the majority remain poorly characterised. Studies of a small number of mutations including the most common, F508del-CFTR, have identified six general mechanisms of CFTR dysfunction. Here, we review selectively progress to understand how CF mutations disrupt CFTR processing, stability and function. We explore CFTR structure and function to explain the molecular mechanisms of CFTR dysfunction and highlight new knowledge of disease pathophysiology emerging from large animal models of CF. Understanding CFTR dysfunction is crucial to the development of transformational therapies for CF patients.

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2002 Mutation of R334, including the CF mutations R334L and R334Q, transformed the current-voltage (I-V) relationship of CFTR from linear (or quasi-linear, see Cai et al., 2003) to strongly inwardly rectifying (Smith et al., 2001; Gong and Linsdell, 2003). Login to comment

[hide] The cystic fibrosis transmembrane conductance regu... Pflugers Arch. 2015 Aug;467(8):1783-94. doi: 10.1007/s00424-014-1618-8. Epub 2014 Oct 4. Broadbent SD, Ramjeesingh M, Bear CE, Argent BE, Linsdell P, Gray MA
The cystic fibrosis transmembrane conductance regulator is an extracellular chloride sensor.
Pflugers Arch. 2015 Aug;467(8):1783-94. doi: 10.1007/s00424-014-1618-8. Epub 2014 Oct 4., [PMID:25277268]

Abstract [show]
The cystic fibrosis transmembrane conductance regulator (CFTR) is a Cl(-) channel that governs the quantity and composition of epithelial secretions. CFTR function is normally tightly controlled as dysregulation can lead to life-threatening diseases such as secretory diarrhoea and cystic fibrosis. CFTR activity is regulated by phosphorylation of its cytosolic regulatory (R) domain, and ATP binding and hydrolysis at two nucleotide-binding domains (NBDs). Here, we report that CFTR activity is also controlled by extracellular Cl(-) concentration ([Cl(-)]o). Patch clamp current recordings show that a rise in [Cl(-)]o stimulates CFTR channel activity, an effect conferred by a single arginine residue, R899, in extracellular loop 4 of the protein. Using NBD mutants and ATP dose response studies in WT channels, we determined that [Cl(-)]o sensing was linked to changes in ATP binding energy at NBD1, which likely impacts NBD dimer stability. Biochemical measurements showed that increasing [Cl(-)]o decreased the intrinsic ATPase activity of CFTR mainly through a reduction in maximal ATP turnover. Our studies indicate that sensing [Cl(-)]o is a novel mechanism for regulating CFTR activity and suggest that the luminal ionic environment is an important physiological arbiter of CFTR function, which has significant implications for salt and fluid homeostasis in epithelial tissues.

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112 To explore the role of phosphorylation further, we studied the effect of deleting the R domain from CFTR (residues 634-836) [12, 7], which removes all the major PKA/PKC Table 1 Summary of the FSK stimulation of whole cell currents and Erev shifts observed with the CFTR constructs used in this study CFTR Construct n FSK Stimulation (%&#b1;SEM) Erev shift (mV&#b1;SEM) WT (50 bc;M ATP) 5 180&#b1;96 15.0&#b1;3.6 WT (100 bc;M ATP) 6 12,000&#b1;6,000 15.2&#b1;3.0 WT (300 bc;M ATP) 8 1,200&#b1;600 17.0&#b1;3.0 WT (1 mM ATP) 24 13,000&#b1;6,000 23.7&#b1;1.8 WT (1.3 mM ATP) 9 1,400&#b1;900 16.7&#b1;2.6 WT (2 mM ATP) 24 6,100&#b1;5,300 16.7&#b1;1.6 WT (5 mM ATP) 7 1,600&#b1;1,000 20.1&#b1;4.4 WT (50 bc;M ATP + 50 bc;M P-ATP) 7 224&#b1;130 15.3&#b1;1.0 WT + Genistein 4 7,600&#b1;5,200 26.1&#b1;5.4 WT + AMP-PNP 5 2,800&#b1;2,500 21.8&#b1;5.5 WT (3 mM MgCl2) 7 28,000&#b1;17,000 18.3&#b1;3.1 R104Q 5 4,600&#b1;1,600 28.6&#b1;4.7 K114C 5 12,000&#b1;6,700 29.2&#b1;3.0 R117Q 4 33,000&#b1;20,000 30.1&#b1;3.4 K329A 5 13,000&#b1;10,000 33.7&#b1;2.1 R334Q 9 13,000&#b1;6,700 27.3&#b1;2.9 K335A 5 3,200&#b1;1,500 20.8&#b1;7.1 W401G 7 2,600&#b1;1,800 18.5&#b1;4.8 Delta-R (No Stim) 5 - 25.1&#b1;2.7 Delta-R (No FSK, Genistein) 5 140&#b1;13 22.7&#b1;3.0 Delta-R (FSK, No Genistein) 4 89&#b1;14 15.6&#b1;6.0 Delta-R (FSK + Genistein) 6 639&#b1;432 25.1&#b1;4.9 Delta-R-E1371S (No FSK) 9 - 21.4&#b1;4.8 Delta-R-E1371S (FSK) 4 2,600&#b1;1,400 15.3&#b1;4.7 K892Q 7 16,000&#b1;9,500 36.8&#b1;4.8 R899E 4 1,200&#b1;400 25.0&#b1;2.7 R899K 4 1,600&#b1;900 26.6&#b1;2.9 R899Q 7 5,400&#b1;2,800 30.0&#b1;1.3 R899Q + AMP-PNP 4 72,000&#b1;50,000 15.2&#b1;2.8 R899Q-E1371Q (No FSK) 4 - 18.4&#b1;5.9 R899Q-E1371Q (FSK) 6 107&#b1;48 15.6&#b1;3.0 R1128Q 6 14,000&#b1;6,100 41.1&#b1;4.2 Y1219G 6 3,200&#b1;2,500 19.2&#b1;3.3 E1371Q (No FSK) 6 - 25.5&#b1;3.5 E1371Q (FSK) 8 -28&#b1;9 22.3&#b1;4.0 E1371Q (FSK, No ATP, No GTP) 8 270&#b1;130 19.4&#b1;4.5 E1371Q + AMP-PNP (No FSK) 4 - 24.7&#b1;6.5 E1371Q + AMP-PNP (FSK) 8 180&#b1;170 17.4&#b1;4.0 Vector Control 4 15&#b1;38 - FSK stimulation was calculated as the percentage increase in current density at -60 mV from the Erev, after 5-min exposure to 10 bc;M FSK. Login to comment
162 In support of this conclusion, the stimulating effect of [Cl- ]o cannot be due to the ion entering the pore, since mutations that do affect CFTR Cl-conductance (R104Q, R117Q, R334Q, K335A) have no effect on [Cl- ]o stimulation (Fig. 2), and the one site that is important for sensing (R899) does not affect Cl-conductance [45, 47]. Login to comment

[hide] Interactions between permeant and blocking anions ... Biochim Biophys Acta. 2015 Jul;1848(7):1573-90. doi: 10.1016/j.bbamem.2015.04.004. Epub 2015 Apr 17. Linsdell P
Interactions between permeant and blocking anions inside the CFTR chloride channel pore.
Biochim Biophys Acta. 2015 Jul;1848(7):1573-90. doi: 10.1016/j.bbamem.2015.04.004. Epub 2015 Apr 17., [PMID:25892339]

Abstract [show]
Binding of cytoplasmic anionic open channel blockers within the cystic fibrosis transmembrane conductance regulator (CFTR) Cl(-) channel is antagonized by extracellular Cl(-). In the present work, patch clamp recording was used to investigate the interaction between extracellular Cl(-) (and other anions) and cytoplasmic Pt(NO2)4(2-) ions inside the CFTR channel pore. In constitutively open (E1371Q-CFTR) channels, these different anions bind to two separate sites, located in the outer and inner vestibules of the pore respectively, in a mutually antagonistic fashion. A mutation in the inner vestibule (I344K) that greatly increased Pt(NO2)4(2-) binding affinity also greatly strengthened antagonistic Cl(-):blocker interactions as well as the voltage-dependence of block. Quantitative analysis of ion binding affinity suggested that the I344K mutation strengthened interactions not only with intracellular Pt(NO2)4(2-) ions but also with extracellular Cl(-), and that altered blocker Cl(-)- and voltage-dependence were due to the introduction of a novel type of antagonistic ion:ion interaction inside the pore that was independent of Cl(-) binding in the outer vestibule. It is proposed that this mutation alters the arrangement of anion binding sites inside the pore, allowing both Cl(-) and Pt(NO2)4(2-) to bind concurrently within the inner vestibule in a strongly mutually antagonistic fashion. However, the I344K mutation does not increase single channel conductance following disruption of Cl(-) binding in the outer vestibule in R334Q channels. Implications for the arrangement of ion binding sites in the pore, and their functional consequences for blocker binding and for rapid Cl(-) permeation, are discussed.

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6 However, the I344K mutation does not increase single channel conductance following disruption of Cl-binding in the outer vestibule in R334Q channels. Login to comment
105 Consistent with this model, neutralization of this charge in the R334Q/E1371Q mutant abolished the relationship between intracellular Pt(NO2)4 2- block and extracellular [Cl- ] (Fig. 6A-D). Login to comment
106 Block under low [Cl- ] conditions was weakened by the R334Q mutation (Table 1; also compare results for R334Q/E1371Q in Fig. 6C with E1371Q in Fig. 2D), resulting in a significant increase in Pt KD at all voltages (P b 0.002). Login to comment
108 The R334Q mutation also appeared to increase the voltage-dependence of block (Table 1), although the reasons for this effect are not clear. Login to comment
109 Since the R334Q and I344K mutations in different parts of the pore (Fig. 1) had opposite effects on the [Cl- ]o-sensitivity of Pt(NO2)4 2- block - which was practically abolished in R334Q/E1371Q (Fig. 6) but greatly increased in I344K/E1371Q (Figs. 4, 5) - these mutations were combined to generate a R334Q/I344K/E1371Q mutant. Login to comment
110 Not only did R334Q/I344K/E1371Q channels exhibit strong Pt(NO2)4 2- block (Table 1), but block was also strongly dependent on extracellular [Cl- ] (Fig. 6E-H). Login to comment
111 This confirms that the I344K mutation not only strengthens interactions with intracellular Pt(NO2)4 2- ions but also with extracellular Cl-ions. Furthermore, this effect on interactions with extracellular Cl- appears independent of the presence of a positively charged side chain at position 334: whereas the R334Q mutation abolishes Cl- -dependence of block in E1371Q channels (Fig. 6D), it does not in I344K- bearing E1371Q channels (Fig. 6H). Login to comment
112 Thus, interactions with external Cl- that are lost in R334Q/E1371Q channels are at least partially restored by the I344K mutation. Login to comment
113 To examine if the I344K mutation also resulted in altered interactions with other extracellular anions - and if this effect was also independent of R334 -Pt(NO2)4 2- block was also investigated with other extracellular anions, both in I344K/E1371Q and in R334Q/I344K/ E1371Q channels (Fig. 7). Login to comment
117 Secondly, formate was able to significantly increase Pt KD(0) relative to gluconate in both I344K/E1371Q (Fig. 7G) and in R334Q/I344K/E1371Q (Fig. 7H), unlike in E1371Q where formate had no significant effect (Fig. 3D, E). Login to comment
128 Pt KD(0) (4 mM Cl- ) (bc;M) zb4; (4 mM Cl- ) Pt KD(0) (154 mM Cl- ) (bc;M) zb4; (154 mM Cl- ) E1371Q 183.7 &#b1; 33.2 (9) -0.397 &#b1; 0.030 (9) 441.0 &#b1; 28.6 (7) -0.503 &#b1; 0.026 (7) R899Q/E1371Q 189.9 &#b1; 55.0 (6) -0.362 &#b1; 0.063 (6) 434.0 &#b1; 32.2 (7) -0.458 &#b1; 0.048 (7) K95Q/E1371Q 1110 &#b1; 172 (6)** -0.244 &#b1; 0.022 (6)* 1422 &#b1; 218 (6)** -0.193 &#b1; 0.041 (6)** I344K/E1371Q 6.92 &#b1; 1.48 (6)** -1.589 &#b1; 0.125 (6)** 164.7 &#b1; 27.5 (7)** -1.604 &#b1; 0.080 (7)** R334Q/E1371Q 1081 &#b1; 220 (4)** -0.637 &#b1; 0.106 (4)* 1112 &#b1; 144 (4)** -0.621 &#b1; 0.051 (4)* R334Q/I344K/E1371Q 39.24 &#b1; 7.94 (4)* -1.093 &#b1; 0.037 (4)** 258.3 &#b1; 30.7 (5)* -1.075 &#b1; 0.033 (5)** Fig. 4. Effect of mutations that weaken or strengthen intracellular Pt(NO2)4 2- block. Login to comment
150 External Cl- -dependence of Pt(NO2)4 2- block is abolished in R334Q/ E1371Q (Fig. 6C, D; Fig. 10A), consistent with the positive charge at this site in the outer vestibule of the pore (Fig. 1) being crucial for interactions between the channel and extracellular Cl-ions that are required for ion:ion interactions inside the pore [33,43]. Login to comment
151 Binding of Pt(NO2)4 2- ions to R334Q/E1371Q was somewhat weaker than E1371Q (Fig. 10C; Table 2), consistent with earlier reports that mutations at R334 disrupt blocker binding in the pore inner vestibule, perhaps by a long-range conformational effect on the pore [56]. Login to comment
152 The voltage-dependence of Pt(NO2)4 2-binding is also increased in R334Q/E1371Q (Fig. 10C). Login to comment
153 However, the very low apparent Cl- affinity of R334Q/E1371Q implied by the apparent [Cl- ]-independence of Pt KD in this mutant (Figs. 6D, 10A) precluded quantitative analysis of Pt Kocc(0) and Cl K in this case; the lack of slope illustrated in the relationships in Figs. 6D and 10A imply extremely low Cl-binding affinity, consistent with ablation of the external Cl-binding site. Login to comment
154 Although the R334Q mutant abolished Cl- -dependence of Pt(NO2)4 2- block, the double pore mutant R334Q/I344K/E1371Q showed strongly Cl- -dependent block (Fig. 6E-H; Fig. 10B), suggesting that the presence of the I344K mutant restores Cl-binding that is lost in R334Q/E1371Q. Login to comment
155 Quantitative analysis of data from R334Q/I344K/ E1371Q (Fig. 10; Table 2) suggests that the presence of the second fixed positive charge in the inner vestibule at position 344 still supports strong Pt(NO2)4 2-binding (Fig. 10C), although (as for E1371Q) Pt(NO2)4 2-binding is somewhat weakened by the R334Q mutation (Fig. 10C). Login to comment
156 Binding of Pt(NO2)4 2-to Cl- -occupied channels is similar in R334Q/E1371Q and R334Q/I344K/E1371Q (Fig. 10D), suggesting that R334 plays little or no role in ion:ion interactions in mutant channels bearing a positive charge at position 344. Login to comment
157 Chloride binding also remains strong in R334Q/I344K/E1371Q, although it too is somewhat weakened by the R334Q mutation (Fig. 10E). Login to comment
158 The strong effect of external Clon Pt(NO2)4 2-binding to R334Q/I344K/E1371Q channels is illustrated in Fig. 9D. Login to comment
168 (A, B, E, F) Example macroscopic I-V relationships for R334Q/E1371Q (A, B) or R334Q/I344K/E1371Q (E, F) under high (154 mM; A, E) or low (4 mM; B, F) extracellular [Cl- ] conditions. In each case currents were recorded before (control) and after the addition of Pt(NO2)4 2- (at the concentrations indicated) to the intracellular solution. Login to comment
172 There was no significant difference in these parameters for R334Q/E1371Q (E) (P N 0.5). Login to comment
178 These interactions may be important for maximization of single channel conductance (see Introduction), as exemplified by the very low conductance observed for R334Q and for other substitutions at this site [33]. Login to comment
179 However, the reduced single channel conductance observed in R334Q channels (Fig. 12) was not significantly rescued by the I344K mutation (Fig. 12). Login to comment
183 (A, B) Example macroscopic I-V relationships for I344K/E1371Q (A) or R334Q/I344K/E1371Q (B) with extracellular solution containing 150 mM SCN- . Login to comment
221 Because of the lack of [Cl- ]o-dependence in R334Q/E1371Q, values for Pt Kocc, Pt zb4;occ, Cl K and Cl zb4; could not be obtained for this mutant. Login to comment
222 Pt Kvac(0) (bc;M) Pt zb4;vac Pt Kocc(0) (bc;M) Pt zb4;occ Cl K (mM) Cl zb4; E1371Q 245 -0.39 1440 -0.63 179 +0.22 K95Q/E1371Q 1150 -0.23 4400 -0.58 296 +0.20 I344K/E1371Q 0.174 -0.42 978 -1.12 0.264 +1.09 R334Q/E1371Q 1120 -0.71 - - - - R334Q/I344K/E1371Q 31.8 -1.04 1500 -1.15 232 +0.23 Fig. 9. Effect of bound extracellular Cl-ions on the binding of intracellular Pt(NO2)4 2- ions. Login to comment
233 Indeed, the R334Q mutation significantly decreases Pt(NO2)4 2-binding affinity (Fig. 10C; Table 1). Login to comment
241 Analysis of Pt(NO2)4 2- and Cl-binding to channel variants containing the R334Q mutation. Login to comment
242 (A, B) Effect of extracellular [Cl- ] ([Cl- ]o) on the measured Pt KD in R334Q/E1371Q (A) and R334Q/I344K/E1371Q (B) at different membrane potentials as indicated. Login to comment
246 Note that, because of the apparent lack of effect of external Clon Pt(NO2)4 2- block in R334Q/ E1371Q, it was not possible to obtain values for Pt Kocc or Cl K for this mutant. Login to comment
266 However, the R334Q mutation has only a minor impact on Cl-binding in the presence of I344K, and Cl-binding to the R334Q/I344K/E1371Q mutant remains strong and strongly voltage-dependent (Fig. 10; Table 2). Login to comment
268 Indeed, knock-off of Pt(NO2)4 2- by Cl- appears similar in I344K/ E1371Q and R334Q/I344K/E1371Q channels (Fig. 10D), suggesting that anion binding near R334 plays little role in ion:ion interactions that occur in channels bearing the I344K mutation. Login to comment
271 The apparent anion selectivity of the external anion binding site is also slightly altered in I344K-containing channels (Fig. 7G, H), and this appears independent of the presence or absence of the R334Q mutation. Login to comment
275 Single channel conductance of R334Q-containing channels. Login to comment
276 (A) Example single-channel currents recorded at a membrane potential of -60 mV for the wild type, R334Q, and R334Q/I344K channels as indicated. Login to comment
282 strengthoftheinteractionbetweenthem,isalteredinI344K-containingchan- nels.Thus,thedestabilizingeffectofCl- onPt(NO2)4 2-binding-evaluated fromthedifferencebetweenPt(NO2)4 2- bindinginvacantandCl- -occupied channels(i.e.betweenPt KvacandPt Kocc)-ismuchgreaterinI344K/E1371Q (and to a lesser extent R334Q/I344K/E1371Q) than in E1371Q or K95Q/ E1371Q(Fig.9).Strengthenedinteractionsbetweenboundanionsarealso suggestedbytheincreasedapparentcouplingbetweenthemovementof Pt(NO2)4 2- andCl- ionsinsidetheporeinI344K(Fig.8E). Login to comment
287 These different mechanisms are illustrated in wild type (A, C) and R334Q/I344K channels (B, D) that are proposed to isolate the two different mechanisms of ion:ion interaction; it is presumed that both mechanisms are active in I344K (and neither in R334Q). Login to comment
289 (B) In R334Q/I344K channels, Cl- does not bind to the outer pore mouth, but instead binds further into the pore from its extracellular end (experiencing a greater fraction of the transmembrane electric field) and binds close to the introduced lysine in the inner vestibule, where it strongly antagonizes Pt(NO2)4 2-binding (leading to very strong [Cl- ]o-dependence of block). Login to comment
291 (D) In R334Q/I344K, even if multiple Cl-ions are able to bind close together in the inner vestibule, this does not result in rapid Cl-permeation in the absence of Cl-binding to the outer pore region. Login to comment
297 In effect, in the R334Q/I344K double pore mutant, one kind of antagonistic Cl- :blocker interaction (Fig. 13A) has been replaced by another with a different molecular mechanism (Fig. 13B). Login to comment
312 However, although I344K appears capable of restoring sensitivity to external Cl-ions that is lost in R334Q, this does not result in a significant restoration of unitary Cl-conductance (Fig. 12). Login to comment
313 In other words, although it is suggested that in R334Q/I344K channels one form of knock-off inside the pore has been replaced by another (Fig. 13B), this surrogate knock-off mechanism does not appear to be capable of supporting high Cl-conductance in the way that normal ion-ion interactions in wild type CFTR are proposed to do (Fig. 13C, D). Login to comment

[hide] Single-cell high resolution melting analysis: A no... J Cyst Fibros. 2015 Oct 19. pii: S1569-1993(15)00217-9. doi: 10.1016/j.jcf.2015.09.009. Destouni A, Poulou M, Kakourou G, Vrettou C, Tzetis M, Traeger-Synodinos J, Kitsiou-Tzeli S
Single-cell high resolution melting analysis: A novel, generic, pre-implantation genetic diagnosis (PGD) method applied to cystic fibrosis (HRMA CF-PGD).
J Cyst Fibros. 2015 Oct 19. pii: S1569-1993(15)00217-9. doi: 10.1016/j.jcf.2015.09.009., [PMID:26493493]

Abstract [show]
BACKGROUND: Institutions offering CF-PGD face the challenge of developing and optimizing single cell genotyping protocols that should cover for the extremely heterogeneous CF mutation spectrum. Here we report the development and successful clinical application of a generic CF-PGD protocol to facilitate direct detection of any CFTR nucleotide variation(s) by HRMA and simultaneous confirmation of diagnosis through haplotype analysis. METHODS: A multiplex PCR was optimized supporting co-amplification of any CFTR exon-region, along with 6 closely linked STRs. Single cell genotypes were established through HRM analysis following melting of the 2nd round PCR products and were confirmed by STR haplotype analysis of the 1st PCR products. The protocol was validated pre-clinically, by testing 208 single lymphocytes, isolated from whole blood samples from 4 validation family trios. Fifteen PGD cycles were performed and 103 embryos were biopsied. RESULTS: In 15 clinical PGD cycles, genotypes were achieved in 88/93 (94.6%) embryo biopsy samples, of which 57/88 (64.8%) were deemed genetically suitable for embryo transfer. Amplification failed at all loci for 10/103 blastomeres biopsied from poor quality embryos. Six clinical pregnancies were achieved (2 twin, 4 singletons). PGD genotypes were confirmed following conventional amniocentesis or chorionic villus sampling in all achieved pregnancies. CONCLUSIONS: The single cell HRMA CF-PGD protocol described herein is a flexible, generic, low cost and robust genotyping method, which facilitates the analysis of any CFTR genotype combination. Single-cell HRMA can be beneficial to other clinical settings, for example the detection of single nucleotide variants in single cells derived from clinical tumor samples.

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79 Validation case no. Genotype combination (HGVS CFTR reference sequences NM000492.3 and NG016465.1) Light scanner (LSC) exons (Montgomery et al. 2007) Number of cells tested Amplicons in multiplex RxNa PCR efficiency (%) Overall ADO (%) 1 p.Arg334Gln and c.489+3ANG 7.2 and 4.2 48 8 98.85% 2% 2 p.Phe508del and p.Leu732X 10 and 13.3 60 8 98% 1.66% 3 p.Phe508del and p.Asp110His 10 and 4.1 60 8 96.60% 3.33% 4 p.Phe508del and p.Gly542X 10 and 11 40 8 98% 3% Total lymphocytes tested 208 a RxN: reaction, ADO: allele drop-out 3 The mutation p.Phe508del could otherwise more rapidly be detected by fluorescent fragment analysis by incorporating the relevant primer set in the first PCR. Login to comment
101 PGD case no. Genotype combination (HGVS CFTR reference sequences NM000492.3 and NG016465.1) LSC exons (legacy nomenclature) (Montgomery et al., 2007) No. of blastomeres received for diagnosis No. of blastomeres amplified No. of blastomeres genotyped No. of unaffected blastomeres Pregnancy Confirmation of PGD result by PNDa 1 p.Arg334Gln and c.489+3ANG 7.2 and 4.2 5 4 4 2 No N/A 2 p.Phe508del and p.Phe508del 10 11 10 10 6 Yes Yes 3 p.Phe508del and c.489+1GNT 10 and 4.2 8 7 7 4 Yes Yes 4 p.Phe508del and p.Leu732X 10 and 13.3 10 8 8 5 Yes Yes 5 p.Phe508del and p.Asp1152His 10 and 18 4 3 3 3 Yes Yes 6 p.Phe508del and c.2051_2052delAAinsG 10 and 13.2 5 4 4 3 Yes Yes 7 p.Phe508del and p.Gly1069Arg 10 and 17bA1 9 9 9 4 Yes No (BP) 8 p.Phe508del and p.Gly542X 10 and 11 3 3 3 2 Yes Yes 9 p.Phe508del and c.3140-26ANG 10 and 17bA1 8 8 7 3 No N/A 10 p.Gly542X and p.Gly542X 11 2 2 2 1 No transfer 11 p.Glu826Lys and p.Phe508del 13.4 and 10 6 6 4 3 Yes Miscarried 12 p.D1312G and c.489+1GNT 21 and 4.2 11 9 9 8 Yes Miscarried 13 p.Glu279Asp and p.Phe508del 6b and 10 7 7 5 3 No N/A 14 p.Phe508del and p.Gly1069Arg 10 and 17bA1 9 8 8 5 Yes No (BP) 15 p.Glu822X and p.Gly1069Arg 13.4 and 17bA1 5 5 5 5 Yesb Miscarried Total 103 93 88 57 N/A: non-applicable, BP: biochemical pregnancy. Login to comment