ABCMdb

ABCA4 p.Leu11Pro

ClinVar:	c.32T>C , p.Leu11Pro ? , not provided
Predicted by SNAP2:	A: N (53%), C: N (61%), D: D (71%), E: D (53%), F: N (72%), G: D (71%), H: N (53%), I: N (93%), K: D (53%), M: N (93%), N: D (59%), P: D (91%), Q: N (57%), R: D (95%), S: D (53%), T: N (66%), V: N (82%), W: D (63%), Y: N (66%),
Predicted by PROVEAN:	A: D, C: D, D: D, E: D, F: D, G: D, H: D, I: N, K: D, M: N, N: D, P: D, Q: D, R: D, S: D, T: D, V: N, W: D, Y: D,

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[hide] Spectrum of ABCR gene mutations in autosomal reces... Eur J Hum Genet. 1998 May-Jun;6(3):291-5. Rozet JM, Gerber S, Souied E, Perrault I, Chatelin S, Ghazi I, Leowski C, Dufier JL, Munnich A, Kaplan J
Spectrum of ABCR gene mutations in autosomal recessive macular dystrophies.
Eur J Hum Genet. 1998 May-Jun;6(3):291-5., [PMID:9781034]

Abstract [show]
Stargardt disease (STGD) and late-onset fundus flavimaculatus (FFM) are autosomal recessive conditions leading to macular degenerations in childhood and adulthood, respectively. Recently, mutations of the photoreceptor cell-specific ATP binding transporter gene (ABCR) have been reported in Stargardt disease. Here, we report on the screening of the whole coding sequence of the ABCR gene in 40 unrelated STGD and 15 FFM families and we show that mutations truncating the ABCR protein consistently led to STGD. Conversely, all mutations identified in FFM were missense mutations affecting uncharged amino acids. These results provide the first genotype-phenotype correlations in ABCR gene mutations.

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45 Furthermore, all ABCR missense mutations Table 1 Mutations in the ABCR gene in STGD and FFM families Conserved aa in: Nucleotide change Amino acid change Domain ABCs RmP Phenotype Families Comment (571-2)A®G splicing mutation STGD 1 HAD1 (1938-2)A®G splicing mutation STGD 1 (4668+2)T®C splicing mutation STGD 1 (4735+2)T®A splicing mutation STGD 1 del(5196+1-5196+6 splicing mutation STGD 1 LOZ2 2570 delT frameshift mutation STGD 1 3209insGT frameshift mutation STGD 2 CHE2 G3754T E1252X STGD 1 C3994T Q1332X STGD 1 C6337G I2113X STGD 1 JEG2 C52T R18W IC - + STGD 1 C634T R212C EC - + STGD 5 GEN2, JEG2 G1908T Q636H IC - + STGD 1 LOZ2 C3056T T1019M IC - + STGD 1 C3322T R1107C IC - + STGD 1 JUL2 C4916T R1640W IC + + STGD 2 MAR1 G5929A G1977S ATP2 + + STGD 1 GEN2 G6320A R2107H IC + + STGD 1 JUL2 C3114T A1038V IC - + STGD 2 CHE2 +FFM +1 VII2 T1622C L541P EC - + FFM 1 VII2 T31C L11P IC + + FFM 1 G3272A G1090E IC + + FFM 1 G4522T G1508C IC + + FFM 1 C5908T L1970F IC + + FFM 1 GON2 T5912G L1971R IC + + FFM 1 GON2 Mutations refer to the standard nomenclature. Login to comment

[hide] ABCA4 disease progression and a proposed strategy ... Hum Mol Genet. 2009 Mar 1;18(5):931-41. Epub 2008 Dec 12. Cideciyan AV, Swider M, Aleman TS, Tsybovsky Y, Schwartz SB, Windsor EA, Roman AJ, Sumaroka A, Steinberg JD, Jacobson SG, Stone EM, Palczewski K
ABCA4 disease progression and a proposed strategy for gene therapy.
Hum Mol Genet. 2009 Mar 1;18(5):931-41. Epub 2008 Dec 12., [PMID:19074458]

Abstract [show]
Autosomal recessive retinal diseases caused by mutations in the ABCA4 gene are being considered for gene replacement therapy. All individuals with ABCA4-disease show macular degeneration, but only some are thought to progress to retina-wide blindness. It is currently not predictable if or when specific ABCA4 genotypes will show extramacular disease, and how fast it will progress thereafter. Early clinical trials of focal subretinal gene therapy will aim to arrest disease progression in the extramacular retina. In 66 individuals with known disease-causing ABCA4 alleles, we defined retina-wide disease expression by measuring rod- and cone-photoreceptor-mediated vision. Serial measurements over a mean period of 8.7 years were consistent with a model wherein a normal plateau phase of variable length was followed by initiation of retina-wide disease that progressed exponentially. Once initiated, the mean rate of disease progression was 1.1 log/decade for rods and 0.45 log/decade for cones. Spatio-temporal progression of disease could be described as the sum of two components, one with a central-to-peripheral gradient and the other with a uniform retina-wide pattern. Estimates of the age of disease initiation were used as a severity metric and contributions made by each ABCA4 allele were predicted. One-third of the non-truncating alleles were found to cause more severe disease than premature truncations supporting the existence of a pathogenic component beyond simple loss of function. Genotype-based inclusion/exclusion criteria and prediction of the age of retina-wide disease initiation will be invaluable for selecting appropriate candidates for clinical trials in ABCA4 disease.

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151 Estimated severity of ABCA4 alleles and their properties ABCA4 allele Delay of retina-wide disease initiation (years)a In vitro or in vivo studiesb Molecular structural localizationc C2150Y 225.8 NBD-2 A1038V;L541P 214.0 35, 38 ECD-1/NBD-1 IVS38-10 T.C 211.1 L244P 25.7 ECD-1 E1122K 23.5 NBD-1 C54Y 22.1 35 ECD-1 IVS35þ2 T.C 22.1 R602W 21.8 38 ECD-1 V1896D 21.8 TM12 L1940P 21.4 NBD-2 Truncation mutationsd 0.0 E1087D 2.8 NBD-1 R220C 3.9 ECD-1 A1598D 3.9 ECD-2 R1640Q 3.9 ECD-2 R1098C 4.9 NBD-1 P1380L 7.4 35 TM7 N965S 7.6 35 NBD-1 V1433I 8.6 ECD-2 R1108C 10.4 35 NBD-1 T1526M 14.5 35 ECD-2 R2030Q 14.5 NBD-2 L2027F 15.1 35,37 NBD-2 G818E 17.3 35 TM5/TM6 S100P 18.2 ECD-1 L1201R 18.2 NBD-1 R18W 18.5 Nt D600E 18.5 ECD-1 L11P 21.7 Nt D654N 25.3 36 ECD-1 K2172R 27.9 NBD-2 IVS40þ5 G.A 28.1 G1961E 37.9 35 NBD-2 G1961R 44.0 NBD-2 a Delay of retina-wide disease initiation relative to the standard of age 10.6 years. Login to comment

[hide] ABCA4 mutations in Portuguese Stargardt patients: ... Mol Vis. 2009;15:584-91. Epub 2009 Mar 25. Maia-Lopes S, Aguirre-Lamban J, Castelo-Branco M, Riveiro-Alvarez R, Ayuso C, Silva ED
ABCA4 mutations in Portuguese Stargardt patients: identification of new mutations and their phenotypic analysis.
Mol Vis. 2009;15:584-91. Epub 2009 Mar 25., [PMID:19365591]

Abstract [show]
PURPOSE: To resolve the spectrum of causative retina-specific ATP-binding cassette transporter gene (ABCA4) gene mutations in Portuguese Stargardt (STGD) patients and compare allele frequencies obtained in this cohort with those of previous population surveys. METHODS: Using a microarray technique (ABCR400 gene chip), we screened all previously reported ABCA4 gene mutations in the genomic DNA of 27 patients from 21 unrelated Stargardt families whose phenotypes had been clinically evaluated using psychophysics and electrophysiological measurements. Furthermore, we performed denaturing high performance liquid chromatography whenever one or both mutant alleles failed to be detected using the ABCR gene chip. RESULTS: A total of 36 mutant alleles (out of the 54 tested) were identified in STGD patients, resulting in a detection rate of 67%. Two mutant alleles were present in 12 out of 21 STGD families (57%), whereas in four out of 21 (19%) of the families, only one mutant allele was found. We report the presence of 22 putative pathogenic alterations, including two sequence changes not found in other populations, c.2T>C (p.Met1Thr) and c.4036_4037delAC (p.Thr1346fs), and two novel disease-associated variants, c.400C>T (p.Gln134X) and c.4720G>T (p.Glu1574X). The great majority of the mutations were missense (72.7%). Seven frameshift variants (19.4%), three nonsense mutations (8.3%), and one splicing sequence change (2.7%) were also found in STGD chromosomes. The most prevalent pathologic variant was the missense mutation p.Leu11Pro. Present in 19% of the families, this mutation represents a quite high prevalence in comparison to other European populations. In addition, 23 polymorphisms were also identified, including four novel intronic sequence variants. CONCLUSIONS: To our knowledge, this study represents the first report of ABCA4 mutations in Portuguese STGD patients and provides further evidence of different mutation frequency across populations. Phenotypic characterization of novel putative mutations was addressed.

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8 The most prevalent pathologic variant was the missense mutation p.Leu11Pro. Login to comment
64 Most of the mutations detected have been reported as STGD-associated variants: p.Met1Val, p.Asn96Asp, p.Arg290Trp, p.Val931Met, p.Gly1961Glu, p.Leu2027Phe, p.Arg2030Gln, p.Asp1048fs, and IVS40+5G>A. Login to comment
65 Although most of the mutations were found in one family, five disease-associated alleles were detected in unrelated STGD families (p.Leu11Pro, p.Asp1048fs; p.Gly1961Glu; p.Ser1642Arg; p.Val1681_Cys1685del; p.Val931Met). Login to comment
69 4139C>T(28) p.Asn96Asp [30]/p.Pro1380Leu [13] 2 4458 Mi 5 8/10 / 6/10 ND / ND ND/ND 4455 S 8 1/10 / 8/10 ND / ND ND/ND 3 4431 Mo 6 1,6/10 / 1,6/10 c.1804C>T(13) / c.IVS+5G>A(40) p.Arg602Trp [30]/SPLICE [11] 4 4626 S 6 FC / FC c.3211_3212insGT(22) / c.3211_3212insGT(22) p.Asp1048fs [5]/p.Asp1048fs [5] 5 4514 S 12 1/10 / 1/10 c.32T>C(1) / c. Login to comment
70 [1A>G(1)]+[6089G>A(44)] p.Leu11Pro [12]/p.(Met1Val [6])+(Arg2030Gln [9]) 6 4525 Mo 14 1/10 / 1/10 ND / c.868C>T(8) ND/p.Arg290Trp [6] 7 4585 Mo 11 0.5/10 / 0.5/10 c.6079C>T(44) / ND p.Leu2027Phe [5]/ND 8 4678 Mo 9 0.5/10 / 1/10 c.3113C>T(21) / c.3602T>G(24) p.Ala1038Val [5]/p.Leu1201Arg [9] 9 4675 Mo 7 0.5/10 / 1/10 c.2T<C(1) / c.2T<C(1) p.Met1Thr/p.Met1Thr 10 4737 Mo 24 1.2/10 / 1.2/10 c.5882G>A(42) / c.3211_3212insGT(22) p.Gly1961Glu [4]/p.Asp1048fs 11 4613 S 9 FC / FC c. Login to comment
72 (Ser1642Arg [10])+(Val1681_Cys1685del [10])/ p.Leu11Pro 12 4796 Mo 43 1/10 / 3/10 c.4720G>T(33) / c.2791G>A(19) p.Glu1574X/p.Val931Met [5] 13 4859 Mo 30 0.5/10 / 0.5/10 c.5882G>A(42) / ND p.Gly1961Glu/ND 5472 Mo 30 6/10 / 8/10 c.5882G>A(42) / ND p.Gly1961Glu/ND 14 4974 S 7 1/10 / 1/10 c.4036_4037delAC(27) / c.400C>T(4) p.Thr1346fs/p.Gln134X 4975 S 7 1/10 / 1/10 c. Login to comment
73 4036_4037delAC(27) / c.400C>T(4) p.Thr1346fs/p.Gln134X 15 5193 Mo 9 1/10 / 1/10 ND / ND ND/ND 16 5138 Mo 27 1/10 / 1/10 ND / ND ND/ND 17 5111 Mo 29 2.5/10 / 1.6/10 c.1928T>G(13) / ND p.Val643Gly/ND 5137 Mo 25 3/10 / FC ND / c.32T>C(1) ND/p.Leu11Pro 18 5709 Mi 9 2/10 / 2/10 c.32T>C(1) / c.1804C<T(13) p.Leu11Pro/p.Arg602Thr [9] 19 5434 Mo 17 2/10 / 2/10 c. Login to comment
81 most prevalent disease-associated variant was the missense mutation p.Leu11Pro, accounting for 11% (4/36) of the disease chromosomes. Login to comment
71 (Ser1642Arg [10])+(Val1681_Cys1685del [10])/ p.Leu11Pro 12 4796 Mo 43 1/10 / 3/10 c.4720G>T(33) / c.2791G>A(19) p.Glu1574X/p.Val931Met [5] 13 4859 Mo 30 0.5/10 / 0.5/10 c.5882G>A(42) / ND p.Gly1961Glu/ND 5472 Mo 30 6/10 / 8/10 c.5882G>A(42) / ND p.Gly1961Glu/ND 14 4974 S 7 1/10 / 1/10 c.4036_4037delAC(27) / c.400C>T(4) p.Thr1346fs/p.Gln134X 4975 S 7 1/10 / 1/10 c. Login to comment
80 most prevalent disease-associated variant was the missense mutation p.Leu11Pro, accounting for 11% (4/36) of the disease chromosomes. Login to comment

[hide] Evidence of widespread retinal dysfunction in pati... Invest Ophthalmol Vis Sci. 2008 Mar;49(3):1191-9. Maia-Lopes S, Silva ED, Silva MF, Reis A, Faria P, Castelo-Branco M
Evidence of widespread retinal dysfunction in patients with stargardt disease and morphologically unaffected carrier relatives.
Invest Ophthalmol Vis Sci. 2008 Mar;49(3):1191-9., [PMID:18326749]

Abstract [show]
PURPOSE: To characterize contrast sensitivity (CS) across the visual field for two achromatic spatial-temporal frequencies in 21 families with Stargardt disease (STGD) and to correlate psychophysical impairment with patterns of change in multifocal electroretinography (mfERG). METHODS: Twenty-seven eyes from patients with STGD, 16 eyes from asymptomatic relatives, and 44 age-matched control eyes were included. Chromatic CS function was assessed by comparing protan, deutan, and tritan (Cambridge Color Test; Cambridge Research Systems Ltd., Rochester, UK) and anomaloscope measures (IF-2; Roland Consult, Wiesbaden, Germany). Achromatic CS measures were obtained with custom-made software in nine locations by using randomly interleaved staircases. The first task-low spatial frequency (LSF)-matched the known frequency-doubling method that is believed to activate the magnocellular pathway preferentially. The second included an intermediate spatial frequency (ISF, 3.5 cyc/deg). mfERGs (RETIscan; Roland Consult) were also obtained. Relatives were screened for ABCA4 mutations by ABCR400 microarray and direct sequencing. RESULTS: Central impairment of achromatic and chromatic CS (along the three isolation axes) was observed in STGD. LSF and ISF tasks revealed significant and widespread dysfunction in patients and their morphologically unaffected relatives, 80% of whom were found to be ABCA4 mutation carriers. Significant reduction of P1 amplitudes was also observed in both groups. CONCLUSIONS: CS function is impaired in patients with STGD at distinct spatial-temporal frequencies, which, in addition to the color vision deficits, suggests dual impairment of the magno- parvocellular pathways. STGD morphologically unaffected carriers may show patterns of psychophysical dysfunction that are mirrored by abnormal mfERG responses.

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149 The most frequent mutation found was the missense variant G1961E (6.7%) that, even in the heterozygous state, has been significantly associated with age-related macular degeneration (AMD).16 One missense mutation involving an uncharged amino acid (L11P) in a conserved domain that has been found in FFM patients was detected. Login to comment
133 The most frequent mutation found was the missense variant G1961E (6.7%) that, even in the heterozygous state, has been significantly associated with age-related macular degeneration (AMD).16 One missense mutation involving an uncharged amino acid (L11P) in a conserved domain that has been found in FFM patients was detected. Login to comment

[hide] Spectrum of the ABCA4 gene mutations implicated in... Invest Ophthalmol Vis Sci. 2007 Mar;48(3):985-90. Valverde D, Riveiro-Alvarez R, Aguirre-Lamban J, Baiget M, Carballo M, Antinolo G, Millan JM, Garcia Sandoval B, Ayuso C
Spectrum of the ABCA4 gene mutations implicated in severe retinopathies in Spanish patients.
Invest Ophthalmol Vis Sci. 2007 Mar;48(3):985-90., [PMID:17325136]

Abstract [show]
PURPOSE: The purpose of this study is to describe the spectrum of mutations in the ABCA4 gene found in Spanish patients affected with several retinal dystrophies. METHODS: Sixty Spanish families with different retinal dystrophies were studied. Samples were analyzed for variants in all 50 exons of the ABCA4 gene by screening with the ABCR400 microarray, and results were confirmed by direct sequencing. Haplotype analyses were also performed. For those families with only one mutation detected by the microarray, denaturing (d)HPLC was performed to complete the mutational screening of the ABCA4 gene. RESULTS: The sequence analysis of the ABCA4 gene led to the identification of 33 (27.5%) potential disease-associated alleles among the 60 patients. These comprised 16 distinct sequence variants in 25 of the 60 subjects investigated. For autosomal recessive cone-rod dystrophy (arCRD), we found that 50% of the CRD families with the mutation had two recurrent changes (2888delG and R943Q). For retinitis pigmentosa (RP) and autosomal dominant macular dystrophy (adMD), one putative disease-associated allele was identified in 9 of the 27 and 3 of the 7 families, respectively. CONCLUSIONS: In the population studied, ABCA4 plays an important role in the pathogenesis of arCRD. However, mutations in this gene are less frequently identified in other retinal dystrophies, like RP or adMD, and therefore it is still not clear whether ABCA4 is involved as a modifying factor or the relationship is a fortuitous association.

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56 TABLE 1. Genetic Analyses of ABCA4 Mutations in Three Families with Autosomal Dominant Macular Dystrophy Family Allele 1 Allele 2 Haplotype AnalysisNucleotide Change Amino Acid Change Nucleotide Change Amino Acid Change ADDM-59 [5582G3A; 6764G3T] [G1961E; S22551] Excluded ADDM-92 466A3G I156V Not done ADDM-105 2828G3A R943Q Not done No change has been detected as allele 2. Login to comment
57 TABLE 2. Genetic Analyses of ABCA4 Mutations in 13 arCRD Families Family Allele 1 Allele 2 Haplotype AnalysisNucleotide Change Amino Acid Change Nucleotide Change Amino Acid Change ARDM-79 2888delG Frameshift 2888delG Frameshift Cosegregates ARDM-85 6764G3T S2255I (likely nonpathogenic) Not detected Not done* ARDM-86 2888delG Frameshift 2888delG Frameshift Cosegregates ARDM-99 4297G3A V1433I Not detected Not done* ARDM-126 [2828G3A; 5929G3A] [R943Q; G1977S] [2828G3A; 5929G3A] [R943Q; G1977S] Cosegregates ARDM-133 32T3C L11P 2888delG Frameshift Cosegregates ARDM-134 2828G3A R943Q Excluded ARDM-174 4918C3T R1640W c.6147؉2T3A Splice Cosegregates ARDM-176 2888delG Frameshift 6179T3G L2060R Cosegregates RP-267 5041del 15 pb Frameshift 5041del 15 pb Frameshift Cosegregates RP-577 1140T3A N380K Not detected Not done* SRP-964 2828G3A R943Q Not detected Not done* B210 2828G3A R943Q 2701A3G T901A Not done* The mutation detected by dHPLC is in bold. Login to comment
108 In the two 2888delG compound heterozygous families, one of them showed the missense mutation L11P, which affects a conserved amino acid localized in the intracytoplasmic compartment,8 as a second allele, and the other family harbored the L2060R mutation, which produces an alteration in the charge of the mutated amino acid that has been associated with the CRD phenotype.20 In this work, we found that the diagnosis of the proband from family ARDM-79 had changed from arSTGD to arCRD. Login to comment
106 In the two 2888delG compound heterozygous families, one of them showed the missense mutation L11P, which affects a conserved amino acid localized in the intracytoplasmic compartment,8 as a second allele, and the other family harbored the L2060R mutation, which produces an alteration in the charge of the mutated amino acid that has been associated with the CRD phenotype.20 In this work, we found that the diagnosis of the proband from family ARDM-79 had changed from arSTGD to arCRD. Login to comment

[hide] Outcome of ABCA4 disease-associated alleles in aut... Ophthalmology. 2013 Nov;120(11):2332-7. doi: 10.1016/j.ophtha.2013.04.002. Epub 2013 Jun 4. Riveiro-Alvarez R, Lopez-Martinez MA, Zernant J, Aguirre-Lamban J, Cantalapiedra D, Avila-Fernandez A, Gimenez A, Lopez-Molina MI, Garcia-Sandoval B, Blanco-Kelly F, Corton M, Tatu S, Fernandez-San Jose P, Trujillo-Tiebas MJ, Ramos C, Allikmets R, Ayuso C
Outcome of ABCA4 disease-associated alleles in autosomal recessive retinal dystrophies: retrospective analysis in 420 Spanish families.
Ophthalmology. 2013 Nov;120(11):2332-7. doi: 10.1016/j.ophtha.2013.04.002. Epub 2013 Jun 4., [PMID:23755871]

Abstract [show]
OBJECTIVE: To provide a comprehensive overview of all detected mutations in the ABCA4 gene in Spanish families with autosomal recessive retinal disorders, including Stargardt's disease (arSTGD), cone-rod dystrophy (arCRD), and retinitis pigmentosa (arRP), and to assess genotype-phenotype correlation and disease progression in 10 years by considering the type of variants and age at onset. DESIGN: Case series. PARTICIPANTS: A total of 420 unrelated Spanish families: 259 arSTGD, 86 arCRD, and 75 arRP. METHODS: Spanish families were analyzed through a combination of ABCR400 genotyping microarray, denaturing high-performance liquid chromatography, and high-resolution melting scanning. Direct sequencing was used as a confirmation technique for the identified variants. Screening by multiple ligation probe analysis was used to detect possible large deletions or insertions in the ABCA4 gene. Selected families were analyzed further by next generation sequencing. MAIN OUTCOME MEASURES: DNA sequence variants, mutation detection rates, haplotypes, age at onset, central or peripheral vision loss, and night blindness. RESULTS: Overall, we detected 70.5% and 36.6% of all expected ABCA4 mutations in arSTGD and arCRD patient cohorts, respectively. In the fraction of the cohort where the ABCA4 gene was sequenced completely, the detection rates reached 73.6% for arSTGD and 66.7% for arCRD. However, the frequency of possibly pathogenic ABCA4 alleles in arRP families was only slightly higher than that in the general population. Moreover, in some families, mutations in other known arRP genes segregated with the disease phenotype. CONCLUSIONS: An increasing understanding of causal ABCA4 alleles in arSTGD and arCRD facilitates disease diagnosis and prognosis and also is paramount in selecting patients for emerging clinical trials of therapeutic interventions. Because ABCA4-associated diseases are evolving retinal dystrophies, assessment of age at onset, accurate clinical diagnosis, and genetic testing are crucial. We suggest that ABCA4 mutations may be associated with a retinitis pigmentosa-like phenotype often as a consequence of severe (null) mutations, in cases of long-term, advanced disease, or both. Patients with classical arRP phenotypes, especially from the onset of the disease, should be screened first for mutations in known arRP genes and not ABCA4.

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91 Almost all disease-associated variants were found in both arSTGD and arCRD phenotypes in our cohort, with the exception of p.Leu11Pro, p.Arg18Trp, p.Ala538Val, and p.Val1973*, which were associated only with CRD. Login to comment

[hide] Identification of three ABCA4 sequence variations ... Am J Ophthalmol. 2013 Dec;156(6):1220-1227.e2. doi: 10.1016/j.ajo.2013.07.008. Epub 2013 Sep 4. Utz VM, Chappelow AV, Marino MJ, Beight CD, Sturgill-Short GM, Pauer GJ, Crowe S, Hagstrom SA, Traboulsi EI
Identification of three ABCA4 sequence variations exclusive to African American patients in a cohort of patients with Stargardt disease.
Am J Ophthalmol. 2013 Dec;156(6):1220-1227.e2. doi: 10.1016/j.ajo.2013.07.008. Epub 2013 Sep 4., [PMID:24011517]

Abstract [show]
PURPOSE: To describe the clinical and molecular findings in ten unrelated African American patients with Stargardt disease. DESIGN: Retrospective, observational case series. METHODS: We reviewed the clinical histories, examinations, and genotypes of 85 patients with molecular diagnoses of Stargardt disease. Three ABCA4 sequence variations identified exclusively in African Americans were evaluated in 300 African American controls and by in silico analysis. RESULTS: ABCA4 sequence changes were identified in 85 patients from 80 families, of which 11 patients identified themselves as African American. Of these 11 patients, 10 unrelated patients shared 1 of 3 ABCA4 sequence variations: c.3602T>G (p.L1201R); c.3899G>A (p.R1300Q); or c.6320G>A (p.R2107H). The minor allele frequencies in the African American control population for each variation were 7.5%, 6.3%, and 2%, respectively. This is comparable to the allele frequency in African Americans in the Exome Variant Server. In contrast, the allele frequency of all three of these variations was less than or equal to 0.05% in European Americans. Although both c.3602T>G and c.3899G>A have been reported as likely disease-causing variations, one of our control patients was homozygous for each variant, suggesting that these are nonpathogenic. In contrast, the absence of c.6320G>A in the control population in the homozygous state, combined with the results of bioinformatics analysis, support its pathogenicity. CONCLUSIONS: Three ABCA4 sequence variations were identified exclusively in 10 unrelated African American patients: p.L1201R and p.R1300Q likely represent nonpathogenic sequence variants, whereas the p.R2107H substitution appears to be pathogenic. Characterization of population-specific disease alleles may have important implications for the development of genetic screening algorithms.

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121 Population-Specific ABCA4 Alleles in Patients with Stargardt Disease References Population Allele Protein Rivera et al.28 Hargitai et al.12 Hungaro-German c.1622T>C/c.3113C>T p.L541P/p.A1038V September et al.47 Afrikaner c.4469G>A p.C1490Y September et al.47 Afrikaner c.1804C>T p.R602W Rosenberg et al.48 Danish c.2894A>G p.N965S Maugeri et al.27 Western European c.2588G>C p.G863A Maia-Lopes et al.49 Portuguese c.32T>C p.L11P Valverde et al.29 Spanish c.5882G>A p.R1129L Fumagalli et al.50 Italian c.2099G>A p.W700X VOL. 156, NO. 6 ALL AUTHORS HAVE COMPLETED AND SUBMITTED THE ICMJE FORM FOR DISCLOSURE OF POTENTIAL CONFLICTS OF INTEREST, and the following were reported. Login to comment