ABCMdb

ABCA4 p.Val1973*

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[hide] ABCA4 gene analysis in patients with autosomal rec... Eur J Hum Genet. 2008 Jul;16(7):812-9. Epub 2008 Feb 20. Kitiratschky VB, Grau T, Bernd A, Zrenner E, Jagle H, Renner AB, Kellner U, Rudolph G, Jacobson SG, Cideciyan AV, Schaich S, Kohl S, Wissinger B
ABCA4 gene analysis in patients with autosomal recessive cone and cone rod dystrophies.
Eur J Hum Genet. 2008 Jul;16(7):812-9. Epub 2008 Feb 20., [PMID:18285826]

Abstract [show]
The ATP-binding cassette (ABC) transporters constitute a family of large membrane proteins, which transport a variety of substrates across membranes. The ABCA4 protein is expressed in photoreceptors and possibly functions as a transporter for N-retinylidene-phosphatidylethanolamine (N-retinylidene-PE), the Schiff base adduct of all-trans-retinal with PE. Mutations in the ABCA4 gene have been initially associated with autosomal recessive Stargardt disease. Subsequent studies have shown that mutations in ABCA4 can also cause a variety of other retinal dystrophies including cone rod dystrophy and retinitis pigmentosa. To determine the prevalence and mutation spectrum of ABCA4 gene mutations in non-Stargardt phenotypes, we have screened 64 unrelated patients with autosomal recessive cone (arCD) and cone rod dystrophy (arCRD) applying the Asper Ophthalmics ABCR400 microarray followed by DNA sequencing of all coding exons of the ABCA4 gene in subjects with single heterozygous mutations. Disease-associated ABCA4 alleles were identified in 20 of 64 patients with arCD or arCRD. In four of 64 patients (6%) only one mutant ABCA4 allele was detected and in 16 patients (25%), mutations on both ABCA4 alleles were identified. Based on these data we estimate a prevalence of 31% for ABCA4 mutations in arCD and arCRD, supporting the concept that the ABCA4 gene is a major locus for various types of degenerative retinal diseases with abnormalities in cone or both cone and rod function.

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70 of alleles Reference Missense: 6 c.731T4Ca p.L244P 2 23 12 c.1622T4Cb p.L541P 1 5 13 c.1928T4G p.V643G 1 9 17 c.2588G4C p.G863A and p.G863del 2 4 21 c.3113C4Tb p.A1038V 1 4 25 c.3608G4A p.G1203E 1 24 28 c.4139C4T p.P1380L 2 25 30 c.4457C4T p.P1486L 1 25 30 c.4462T4C p.C1488R 1 25 37 c.5285C4A p.A1762D 1 24 41 c.5819T4C p.L1940P 1 26 42 c.5882G4A p.G1961E 1 9 45 c.6148G4C p.V2050L 1 25 45 c.6229C4T p.R2077W 1 25 Nonsense: 6 c.700C4T p.Q234X 1 This study 6 c.735T4G p.Y245X 2 24 28 c.4234C4T p.Q1412X 1 10 Deletion: 24 c.3539_3554del p.S1181PfsX8 1 This study 43 c.5917delG p.V1973X 3 27 Splice site/intronic: 26 c.5196+1G4A Splicing 1 9 34 c.4848+2T4C Splicing 1 This study 36 c.5196+1_5196+4del Splicing 1 15 39 c.5461À10T4C Unknown 8 14 40 c.5714+5G4A Splicing? Login to comment
98 For example, two of our arCRD patients (RCD79/6184 and RCD113/3668) are homozygous for putative null alleles (p.Y245X and p.V1973X). Login to comment

[hide] Association between genotype and phenotype in fami... Mol Vis. 2014 Jan 7;20:89-104. eCollection 2014. Kjellstrom U
Association between genotype and phenotype in families with mutations in the ABCA4 gene.
Mol Vis. 2014 Jan 7;20:89-104. eCollection 2014., [PMID:24453473]

Abstract [show]
PURPOSE: To investigate the genotype and phenotype in families with adenosine triphosphate-binding cassette, sub-family A, member 4 (ABCA4)-associated retinal degeneration. METHODS: Three families with at least one family member with known homozygous or compound heterozygote mutations in the ABCA4 gene were studied. The investigations included full field electroretinography (ff-ERG), multifocal ERG (mERG), Goldmann visual fields, optical coherence tomography (OCT), and standard ophthalmological examination. Microarray (Asper) was used for ABCA4 genotyping. RESULTS: In family 1, the proband (age 23) was homozygote for the c768 G>T mutation. She was diagnosed with cone rod dystrophy (CRD) while her aunt (age 69) was compound heterozygote for the c768 G>T and c2894 A>G mutations and had autosomal recessive retinitis pigmentosa (arRP). The father (age 61) and the mother (age 60) of the proband were asymptomatic carriers of the c768 G>T mutation. In family 2, the proband (age 25) was homozygote for the c5917del. She was diagnosed with CRD. Her father and two sisters were compound heterozygote for the c5917del and c5882 G>A mutations. The eldest sister (age 23) suffered from Stargardt disease (STGD) while the youngest sister (age 12) and their father (age 48) had no visual complaints. Anyhow, their ERG measurements indicated changes corresponding to STGD. The mother (age 42), (heterozygote for the c5917 delG mutation) and the youngest child (age 9; heterozygote for the c5882 G>A mutation) had a normal phenotype. In family 3, the proband (age 43) was compound heterozygote for c768 G>T and c3113 C>T and had been diagnosed with STGD. Her son (age 12), who was homozygote for the c768 G>T mutation, had wider scotomas with earlier onset (age 6), ff-ERG cone responses in the lower range of normality, and reduced mERG. At the moment, he is classified as having STGD but may progress to CRD. The father (age 45) was asymptomatic and heterozygote for the c768 G>T mutation. The patients with progressive disorders (CRD or arRP) had prolonged implicit times for the 30 Hz flicker ff-ERG and the mERG. All patients with two mutations in the ABCA4 gene demonstrated attenuation of retinal thickness on the OCT macular map. CONCLUSIONS: This study confirms that ABCA4 mutations lead to a spectrum of retinal degenerations ranging from STGD to CRD or arRP. At the time of diagnosis, it is not possible to predict the severity of the condition only from genotyping. Our results suggest that prolongation of implicit times for the ff-ERG and/or mERG seem to be associated with progressive conditions such as CRD and arRP. Since ABCA4 mutations are common in the general population, different family members can harbor various combinations of mutations resulting in diverse phenotype and prognosis in the same family, further emphasizing the importance of a combination of genetic and electrophysiological tests at the first visit and follow-up.

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96 Subject ABCA4 allele 1 ABCA4 allele 2 Phenotype* Nucleotide change Effect Nucleotide change Effect 1 Ia c768 G>T V256V/splice c2894 A>G N965S/missense arRP 1 Ib c768 G>T V256V/splice ৄ ৄ NVP 1 Ic c768 G>T V256V/splice ৄ ৄ NVP 1 IIa c768 G>T V256V/splice c768 G>T V256V/splice CRD 2 Ia c5917 delG V1973X/frameshift ৄ ৄ NVP 2 Ib c5917 delG V1973X/frameshift c5882 G>A G1961E/missense STGD 2 IIa c5917 delG V1973X/frameshift c5917 delG V1973X/frameshift CRD 2 IIb c5917 delG V1973X/frameshift c5882 G>A G1961E/missense STGD 2 IIc c5917 delG V1973X/frameshift c5882 G>A G1961E/missense STGD 2 II d c5882 G>A G1961E/missense ৄ ৄ NVP 3 Ia c768 G>T V256V/splice c3113 C>T A1038V/missense STGD 3 Ib c768 G>T V256V/splice ৄ ৄ NVP 3 IIa c768 G>T V256V/splice c768 G>T V256V/splice STGD Abbreviations: arRP; autosomal recessive retinitis pigmentosa, CRD; cone rod dystrophy, STGD; Stargardt disease, NVP; no visual problems *clinical presentation at last visit T able 3. Login to comment