ABCMdb

ABCA4 p.Asn1868Ile

ClinVar:	c.5603A>T , p.Asn1868Ile N , Benign
Predicted by SNAP2:	A: D (59%), C: D (59%), D: N (61%), E: N (66%), F: D (66%), G: N (57%), H: N (72%), I: D (91%), K: N (66%), L: D (63%), M: D (95%), P: D (53%), Q: N (66%), R: N (72%), S: N (78%), T: N (78%), V: D (95%), W: D (85%), Y: D (66%),
Predicted by PROVEAN:	A: D, C: D, D: N, E: N, F: D, G: D, H: N, I: D, K: D, L: D, M: D, P: D, Q: D, R: D, S: N, T: N, V: D, W: D, Y: D,

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[hide] A subgroup of age-related macular degeneration is ... Invest Ophthalmol Vis Sci. 2012 Apr 30;53(4):2112-8. doi: 10.1167/iovs.11-8785. Print 2012 Apr. Fritsche LG, Fleckenstein M, Fiebig BS, Schmitz-Valckenberg S, Bindewald-Wittich A, Keilhauer CN, Renner AB, Mackensen F, Mossner A, Pauleikhoff D, Adrion C, Mansmann U, Scholl HP, Holz FG, Weber BH
A subgroup of age-related macular degeneration is associated with mono-allelic sequence variants in the ABCA4 gene.
Invest Ophthalmol Vis Sci. 2012 Apr 30;53(4):2112-8. doi: 10.1167/iovs.11-8785. Print 2012 Apr., [PMID:22427542]

Abstract [show]
Purpose. Age-related macular degeneration (AMD) is a heterogeneous condition of high prevalence and complex etiology involving genetic as well as environmental factors. By fundus autofluorescence (FAF) imaging, AMD can be classified into several distinct phenotypes, with one subgroup characterized by fine granular pattern with peripheral punctate spots (GPS[+]). Some features of GPS[+] overlap with Stargardt disease (STGD1), a recessive macular dystrophy caused by biallelic sequence variants in the ATP-binding cassette transporter 4 (ABCA4) gene. The aim of this study was to investigate the role of ABCA4 in GPS[+]. Methods. The ABCA4 gene was sequenced in 25 patients with the GPS[+] phenotype and 29 with geographic atrophy (GA)-AMD but no signs of GPS (GPS[-]). In addition, frequencies of risk-increasing alleles at three known AMD susceptibility loci, including complement factor H (CFH), age-related maculopathy susceptibility 2 (ARMS2), and complement component 3 (C3), were evaluated. Results. We demonstrate that GPS[+] is associated significantly with monoallelic ABCA4 sequence variants. Moreover, frequencies of AMD risk-increasing alleles at CFH, ARMS2, and C3 are similar in GPS[+] and STGD1 patients, with risk allele frequencies in both subcategories comparable to population-based control individuals estimated from 3,510 individuals from the NHLBI Exome Sequencing Project. Conclusions. Our data suggest that the GPS[+] phenotype is accounted for by monoallelic variants in ABCA4 and unlikely by the well-established AMD risk-increasing alleles at CFH, ARMS2, and C3. These findings provide support for a complex role of ABCA4 in the etiology of a minor proportion of patients with AMD.

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100 In contrast, variant c.5603A>T (p.N1868I) was significantly enriched in GPS[+] and STGD1 patients, in agreement with previous findings that have led to the suggestion that the polymorphic variant c.5603A>T may act as a risk-increasing factor in ABCA4-related pathology.37 Together, these data strongly suggest that there is no founder effect in the GPS[+] group as frequencies in the common sequence variants of the ABCA4 gene are not different from the GPS[+] group and the European-American NHLBI samples. Login to comment
134 In addition, our analysis of common variant frequencies in the ABCA4 gene showed that c.5603A>T (p.N1868I) is enriched greatly in the GPS[+] group, a variant that has been suggested previously to act as a risk-increasing factor in ABCA4-related pathology.37 Our findings were in accordance with the genotype-phenotype model suggested by Maugeri et al.,7 proposing pathological effects dependent on a threshold of physiological ABCA4 activity. Login to comment
98 In contrast, variant c.5603A>T (p.N1868I) was significantly enriched in GPS[+] and STGD1 patients, in agreement with previous findings that have led to the suggestion that the polymorphic variant c.5603A>T may act as a risk-increasing factor in ABCA4-related pathology.37 Together, these data strongly suggest that there is no founder effect in the GPS[+] group as frequencies in the common sequence variants of the ABCA4 gene are not different from the GPS[+] group and the European-American NHLBI samples. Login to comment
132 In addition, our analysis of common variant frequencies in the ABCA4 gene showed that c.5603A>T (p.N1868I) is enriched greatly in the GPS[+] group, a variant that has been suggested previously to act as a risk-increasing factor in ABCA4-related pathology.37 Our findings were in accordance with the genotype-phenotype model suggested by Maugeri et al.,7 proposing pathological effects dependent on a threshold of physiological ABCA4 activity. Login to comment

[hide] Further associations between mutations and polymor... Invest Ophthalmol Vis Sci. 2011 Aug 5;52(9):6206-12. Print 2011 Aug. Aguirre-Lamban J, Gonzalez-Aguilera JJ, Riveiro-Alvarez R, Cantalapiedra D, Avila-Fernandez A, Villaverde-Montero C, Corton M, Blanco-Kelly F, Garcia-Sandoval B, Ayuso C
Further associations between mutations and polymorphisms in the ABCA4 gene: clinical implication of allelic variants and their role as protector/risk factors.
Invest Ophthalmol Vis Sci. 2011 Aug 5;52(9):6206-12. Print 2011 Aug., [PMID:21330655]

Abstract [show]
PURPOSE: Mutations in ABCA4 have been associated with autosomal recessive Stargardt disease, autosomal recessive cone-rod dystrophy, and autosomal recessive retinitis pigmentosa. The purpose of this study was to determine (1) associations among mutations and polymorphisms and (2) the role of the polymorphisms as protector/risk factors. METHODS: A case-control study was designed in which 128 Spanish patients and 84 control individuals were analyzed. Patient samples presented one or two mutated alleles previously identified using ABCR400 microarray and sequencing. RESULTS: A total of 18 previously described polymorphisms were studied in patients and control individuals. All except one presented a polymorphisms frequency higher than 5% in patients, and five mutations were found to have a frequency >5%. The use of statistical methods showed that the frequency of the majority of polymorphisms was similar in patients and controls, except for the IVS10+5delG, p.Asn1868Ile, IVS48+21C>T, and p.Arg943Gln polymorphisms. In addition, IVS48+21C>T and p.Arg943Gln were found to be in linkage disequilibrium with the p.Gly1961Glu and p.Arg602Trp mutations, respectively. CONCLUSIONS: Although the high allelic heterogeneity in ABCA4 and the wide spectrum of many common and rare polymorphisms complicate the interpretation of clinical relevance, polymorphisms were identified that may act as risk factors (p.Asn1868Ile) and others that may act as protection factors (p.His423Arg and IVS10+5 delG).

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9 The use of statistical methods showed that the frequency of the majority of polymorphisms was similar in patients and controls, except for the IVS10ϩ5delG, p.Asn1868Ile, IVS48ϩ21CϾT, and p.Arg943Gln polymorphisms. Login to comment
12 Although the high allelic heterogeneity in ABCA4 and the wide spectrum of many common and rare polymorphisms complicate the interpretation of clinical relevance, polymorphisms were identified that may act as risk factors (p.Asn1868Ile) and others that may act as protection factors (p.His423Arg and IVS10ϩ5 delG). Login to comment
76 In contrast, the p.Pro1401Pro, p.Asn1868Ile, p.Leu1894Leu, and p.Leu1938Leu variants were less frequently detected among the p.Arg1129Leu patients (Table 3). Login to comment
77 Despite this, p.His423Arg, IVS33ϩ48CϾT, p.Pro1401Pro, p.Leu1894Leu, and p.Leu1938Leu polymorphisms were detected in similar frequencies between p.Arg1129Leu patients and the control population, since no significant differences existed (P ϭ 0.108, 0.542, 0.605, 0.130, and 0.394 respectively). Login to comment
85 Most Frequent ABCA4 Polymorphisms Found in Patients and Controls Exon Nucleotide Change Amino Acid Change Patients n (%) Allele Frequency n (%) Controls n (%) Allele Frequency n (%) P - IVS48؉21C>T SPLICE 13 (10.2) 13 (5.1) 0 (0.0) 0 (0.0) 0.003 - IVS10؉5 delG SPLICE 36 (28.1) 40 (15.6) 39 (46.4) 43 (25.6) 0.006 40 c.5603A>T p.Asn1868Ile 27 (21.1) 30 (11.7) 9 (10,7) 9 (5.3) 0.049 19 c.2828GϾA p.Arg943Gln 13 (10.2) 15 (5.8) 3 (3.6) 3 (1.8) 0.076 45 c.6249CϾT p.Ile2083Ile 14 (10.9) 15 (5.8) 16 (19.0) 18 (10.7) 0.098 49 c.6764GϾT p.Ser2255Ile 13 (10.2) 13 (5.1) 15 (17.9) 16 (9.5) 0.105 10 c.1268AϾG p.His423Arg 68 (53.1) 84 (32.8) 54 (64.3) 60 (35.7) 0.108 40 c.5682GϾC p.Leu1894Leu 70 (54.7) 90 (35.1) 37 (44.0) 41 (24.4) 0.130 42 c.5843CAϾTG p.Pro1948Leu 13 (10.2) 13 (5.1) 14 (16.7) 15 (8.9) 0.164 8 c.981CϾT p.Pro327Pro 2 (1.6) 2 (0.8) 0 (0.0) 0 (0.0) 0.250 6 c.635GϾA p.Arg212His 8 (6.3) 11 (4.3) 8 (9.5) 8 (4.7) 0.377 41 c.5814AϾG p.Leu1938Leu 40 (31.3) 48 (18.7) 31 (36.9) 35 (20.8) 0.394 44 c.6069CϾT p.Ile2023Ile 17 (13.3) 17 (6.6) 14 (16.7) 15 (8.9) 0.495 IVS33ϩ48CϾT SPLICE 109 (85.2) 170 (66.4) 74 (88.1) 93 (55.3) 0.542 28 c.4203CϾA/T p.Pro1401Pro 10 (7.8) 10 (3.9) 5 (6.0) 5 (2.9) 0.605 10 c.1269CϾT p.His423His 8 (6.3) 8 (3.1) 4 (4.8) 4 (2.4) 0.647 42 c.5844AϾG p.Pro1948Pro 36 (28.1) 42 (16.4) 23 (27.4) 25 (14.9) 0.906 46 c.6285TϾC p.Asp2095Asp 39 (30.5) 43 (16.8) 25 (29.8) 27 (16.1) 0.913 Variants revealing significant differences between both groups are shown in bold. Login to comment
86 the patient group: p.Asn1868Ile (P ϭ 0.013) and p.His423Arg (P ϭ 0 0.023) (Table 3). Login to comment
87 The p.Asn1868Ile variant was found in higher proportion in patients than in control individuals (P ϭ 0.049) (Table 2) and was not present in the 82% of the carrier patients of the p.Gly1961Glu mutation (P ϭ 0.013) (Table 3). Login to comment
88 p.Arg602Trp The p.Arg602Trp mutation was found to be the third most prevalent missense variant, with a frequency of 6.3% (Table 1). Login to comment
93 This variant was significantly associated with p.His423Arg (P ϭ 0.014), p.Asn1868Ile (P Ͻ 0.001), and p.Leu1894Leu (P ϭ 0.016), as 100% of the patients carried both the mutation and these polymorphisms (Table 3). Login to comment
94 p.Arg212H is p.Pro327Pro p.H is423Arg p.H is423H is IVS10+5delG p.Arg602Trp p.Arg943G ln c.3211insG T p.Arg1129Leu p.Pro1401Pro IVS33+48C >Tp.Leu1894Leu p-Leu1938Leu p.Pro1948Leu p.Pro1948Pro p.G ly1961G lup.Leu2060Argp.Asp2095Asp IVS48+21C >T - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - p.Asn1868Ile p.Ile2023Ile p.Ile2083Ile p.Ser2255Ile PATIENTSCONTROLS FIGURE 1. Login to comment
100 Except for the IVS10ϩ5delG, p.Asn1868Ile, and IVS48ϩ21CϾT polymorphisms, the remaining polymorphic variants whose frequency was Ͼ5% failed to show any significant differences between patients and control individuals (Table 2; Fig. 1). Login to comment
102 Carriers of the T variant (homozygous and heterozygous) of p.Asn1868Ile are at more than double the risk of developing the disease than normal homozygous variant (OR: ATϩTT ϭ 2.23; 95% CI, 1.01-5.01; P ϭ 0.05; Table 4). Login to comment
109 Association between the Most Frequent ABCA4 Polymorphisms and Mutations Patients Variants Frequency P Status Predicted Effect Mutation, n (%) p.Arg1129Leu 34 (26.6) Present polymorphisms p.His423Arg 94.1% 0.000 Associated Risk IVS33؉48C>T 100% 0.011 Associated Risk IVS10ϩ5delG 20.6% 0.049 Associated Protector p.Leu1938Leu 17.6% 0.033 Associated Protector p.Ser2255Ile 2.9% 0.054 Associated Protector Mutation, n (%) p.Gly1961Glu 18 (14.1) Present polymorphisms p.Pro1948Pro 94.7% 0.000 Associated Risk p.Leu1938Leu 89.5% 0.000 Associated Risk p.Asp2095Asp 78.9% 0.000 Associated Risk IVS48؉21C>T 70.0% 0.000 Associated Risk IVS10؉5delG 57.9% 0.008 Associated Risk p.His423Arg 31.6% 0.016 Associated Protector p.Asn1868Ile 18.7% 0.039 Associated Protector Mutation, n (%) p.Arg602Trp 8 (6.3%) Present polymorphisms p.Arg943Gln 62.5% 0.000 Associated Risk p.Pro1401Pro 25% 0.044 Associated Protector p.Leu1938Leu 0% 0.041 Associated Protector Mutation, n (%) c.3211insGT 7 (5.5%) Present polymorphisms p.His423Arg 100% 0.021 Associated Risk p.Asn1868Ile 100% 0.000 Associated Risk IVS10ϩ5delG 0% 0.047 Associated Protector Mutation, n (%) p.Leu2060Arg 7 (5.5%) Present polymorphisms p.Leu1938Leu 100% 0.000 Associated Risk p.Pro1948Leu 100% 0.000 Associated Risk p.His423Arg 14.3% 0.019 Associated Protector TABLE 4. Login to comment
110 Polymorphisms and Risk of Stargardt Disease Polymorphism Genotype Cases (n ‫؍‬ 128) N Controls (n ‫؍‬ 84) N OR 95% CI P p.His423Arg AA 60 30 1 (reference) AGϩGG 68 54 0.464 0.250-0.863 0.015 IVS10ϩ5 delG Normal 92 45 1 (reference) N/DϩD/D 36 39 0.452 0.254-0.804 0.007 p.Asn1868Ile AA 101 75 1 (reference) ATϩTT 27 9 2.23 0.990-5.015 0.05 0.25-0.80; P ϭ 0.007, respectively). Login to comment
111 However, carriers of the variant sequences of the p.Asn1868Ile polymorphism exhibit a more than twofold risk of developing the disease than normal homozygous variant (OR: ATϩTT ϭ 2.23; 95% CI, 1.01-5.01; P ϭ 0.05; Table 4). Login to comment
112 Moreover, using a SIFT and a Polyphen prediction, the p.Asn1868Ile variant affected protein function. Login to comment
115 Similarly, the p.Asn1868Ile polymorphism is negatively associated with both p.Gly1961Glu and pArg1129Leu mutations and in positive association with the c.3211insGT mutation (Table 3). Login to comment
120 In a Danish population, both ABCA4 gene variants were found, though no possible association was analyzed.18 However, in a German population, 18 individuals were found to have the IVS48ϩ21CϾT polymorphism, of whom 17 had the p.Gly1961Glu mutation.15 As a contrast, p.Asn1868Ile and p.His423Arg are negatively associated with the p.Gly1961Glu mutation. Login to comment
121 p.Asn1868Ile appears at a higher frequency in patients than in controls (P ϭ 0.049), although previous studies have found the variant to occur in higher, albeit insignificant, frequency among the control population.19 The IVS10ϩ5delG polymorphism was first described in 2001 by Webster et al.18 in a study on a Danish population. Login to comment
122 We found this polymorphism, IVS10ϩ5delG, to be associated with the p.Gly1961Glu mutation (P ϭ 0.005). Login to comment
126 The p.Pro1401Pro, p.Asn1868Ile, p.Leu1894Leu, and p.Leu1938Leu polymorphisms, on the other hand, appeared less frequently among patients with the p.Arg1129Leu mutation. Login to comment
127 Except for p.Asn1868Ile, the remaining polymorphisms were found in a similar number of patients and normal control subjects (Table 2). Login to comment
129 The p.Arg943Gln polymorphism is in linkage disequilibrium with the p.Arg602Trp mutation in Spanish STGD (P Ͻ 0.001, Table 3). Login to comment
130 However, in other European studies the p.Arg943Gln variant was detected in linkage disequilibrium with the p.Gly863Ala mutation,18,19,20 and 21 but this mutation has a low frequency in our series of patients, and no association analysis was performed. Login to comment
131 This change has been described showing diminished activity of the ABCA4 protein.11,22 However, using a SIFT and a Polyphen prediction, the p.Arg943Gln variant would not affect the protein function, so it is not clear how it affects the phenotype. Login to comment
139 Except for the IVS10ϩ5delG, p.Asn1868Ile and IVS48ϩ21CϾT polymorphisms, the remaining polymorphic variants showed no significant differences between patients and control individuals. Login to comment
144 However, IVS10ϩ5delG and p.Asn1868Ile did not represent mutational hot spots. Login to comment
148 In conclusion, the p.His423Arg and IVS10ϩ5delG polymorphisms have a protective effect, whereas the p.Asn1868Ile polymorphism is a risk factor for disease. Login to comment
132 Moreover, using a SIFT and a Polyphen prediction, the p.Asn1868Ile variant affected protein function. Login to comment
135 Similarly, the p.Asn1868Ile polymorphism is negatively associated with both p.Gly1961Glu and pArg1129Leu mutations and in positive association with the c.3211insGT mutation (Table 3). Login to comment
140 In a Danish population, both ABCA4 gene variants were found, though no possible association was analyzed.18 However, in a German population, 18 individuals were found to have the IVS48af9;21Cb0e;T polymorphism, of whom 17 had the p.Gly1961Glu mutation.15 As a contrast, p.Asn1868Ile and p.His423Arg are negatively associated with the p.Gly1961Glu mutation. Login to comment
141 p.Asn1868Ile appears at a higher frequency in patients than in controls (P afd; 0.049), although previous studies have found the variant to occur in higher, albeit insignificant, frequency among the control population.19 The IVS10af9;5delG polymorphism was first described in 2001 by Webster et al.18 in a study on a Danish population. Login to comment
146 The p.Pro1401Pro, p.Asn1868Ile, p.Leu1894Leu, and p.Leu1938Leu polymorphisms, on the other hand, appeared less frequently among patients with the p.Arg1129Leu mutation. Login to comment
147 Except for p.Asn1868Ile, the remaining polymorphisms were found in a similar number of patients and normal control subjects (Table 2). Login to comment
159 Except for the IVS10af9;5delG, p.Asn1868Ile and IVS48af9;21Cb0e;T polymorphisms, the remaining polymorphic variants showed no significant differences between patients and control individuals. Login to comment
164 However, IVS10af9;5delG and p.Asn1868Ile did not represent mutational hot spots. Login to comment
168 In conclusion, the p.His423Arg and IVS10af9;5delG polymorphisms have a protective effect, whereas the p.Asn1868Ile polymorphism is a risk factor for disease. Login to comment

[hide] Novel mutations in of the ABCR gene in Italian pat... Eye (Lond). 2010 Jan;24(1):158-64. Epub 2009 Mar 6. Passerini I, Sodi A, Giambene B, Mariottini A, Menchini U, Torricelli F
Novel mutations in of the ABCR gene in Italian patients with Stargardt disease.
Eye (Lond). 2010 Jan;24(1):158-64. Epub 2009 Mar 6., [PMID:19265867]

Abstract [show]
PURPOSE: Stargardt disease (STGD) is the most prevalent juvenile macular dystrophy, and it has been associated with mutations in the ABCR gene, encoding a photoreceptor-specific transport protein. In this study, we determined the mutation spectrum in the ABCR gene in a group of Italian STGD patients. METHODS: The DNA samples of 71 Italian patients (from 62 independent pedigrees), affected with autosomal recessive STGD, were analysed for mutations in all 50 exons of the ABCR gene by the DHPLC approach (with optimization of the DHPLC conditions for mutation analysis) and direct sequencing techniques. RESULTS: In our group of STGD patients, 71 mutations were identified in 68 patients with a detection rate of 95.7%. Forty-three mutations had been already reported in the literature, whereas 28 mutations had not been previously described and were not detected in 150 unaffected control individuals of Italian origin. Missense mutations represented the most frequent finding (59.2%); G1961E was the most common mutation and it was associated with phenotypes in various degrees of severity. CONCLUSIONS: Some novel mutations in the ABCR gene were reported in a group of Italian STGD patients confirming the extensive allelic heterogeneity of this gene-probably related to the vast number of exons that favours rearrangements in the DNA sequence.

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83 In our series, mainly consisting of patients coming from central Italy, G1961E was the most common mutant allele, in congruence with other studies performed in distinct dissimilar European populations.9,20 Nevertheless, the frequency of G1961E mutation (20.4% of our STGD alleles) was higher than in the other Italian Table 3 Summary of the polymorphic variants identified in the ABCR gene in our series of STGD Italian patients Location Polymorphic variants Number of alleles Exon 3 IVS3 þ 26a4g 14 Exon 5 D159 1 Exon 6 R212H 6 Exon 7 IVS7-32t4c 9 Exon 10 H423R 12 Exon 13 D644 1 Exon 14 IVS14 þ 50t4c 1 Exon 15 IVS15-13t4c 2 Exon 16 IVS16-13c4t 1 Exon 19 R943Q 3 Exon 20 L1988 1 Exon 23 Q1169 4 Exon 23 IVS23 þ 25g4a 2 Exon 24 T1176 6 Exon 24 K1182 3 Exon 28 P1401 1 Exon 33 IVS33-39t4c 2 Exon 34 IVS34 þ 16insgtt 4 Exon 38 D1817Q 7 Exon 40 N1868I 3 Exon 40 L1894 16 Exon 41 L1938 15 Exon 42 P1948 23 Exon 44 I2023 5 Exon 44 IVS44-16g4a 5 Exon 44 IVS44 þ 77g4a 1 Exon 45 I2083 5 Exon 46 D2095 19 Exon 48 IVS48 þ 21c4t 3 Exon 49 S2255I 5 studies where this mutation was detected in 11.110 and 9.7% 11 of the screened alleles. Login to comment

[hide] Frequency of ABCA4 mutations in 278 Spanish contro... Br J Ophthalmol. 2009 Oct;93(10):1359-64. Epub 2008 Oct 31. Riveiro-Alvarez R, Aguirre-Lamban J, Lopez-Martinez MA, Trujillo-Tiebas MJ, Cantalapiedra D, Vallespin E, Avila-Fernandez A, Ramos C, Ayuso C
Frequency of ABCA4 mutations in 278 Spanish controls: an insight into the prevalence of autosomal recessive Stargardt disease.
Br J Ophthalmol. 2009 Oct;93(10):1359-64. Epub 2008 Oct 31., [PMID:18977788]

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AIM: To determine the carrier frequency of ABCA4 mutations in order to achieve an insight into the prevalence of autosomal recessive Stargardt disease (arSTGD) in the Spanish population. METHODS: arSTGD patients (n = 133) were analysed using ABCR400 microarray and sequencing. Control subjects were analysed by two different strategies: 200 individuals were screened for the p.Arg1129Leu mutation by denaturing-HPLC and sequencing; 78 individuals were tested for variants with the microarray and sequencing. RESULTS: For the first strategy in control subjects, the p.Arg1129Leu variant was found in two heterozygous individuals, which would mean a carrier frequency for any variant of approximately 6.0% and a calculated arSTGD prevalence of 1:1000. For the second strategy, carrier frequency was 6.4% and therefore an estimated prevalence of the disease of 1:870. CONCLUSION: Calculated prevalence of arSTGD based on the ABCA4 carrier frequency could be considerably higher than previous estimation. This discrepancy between observed (genotypic) and estimated (phenotypic) prevalence could be due to the existence of non-pathological or low penetrance alleles, which may result in late-onset arSTGD or may be implicated in age-related macular degeneration. This situation should be regarded with special care when genetic counselling is given and further follow-up of these patients should be recommended.

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96 These Table 1 ABCA4 sequence variants identified in Spanish control population Mutant alleles Nucleotide change Amino acid change Number of cases Number of alleles Frequency (%) Homozygous individuals Mutations* c.661G.A p.Gly221Arg 1 1 0.64 None c.1140T.A p.Asn380Lys 1 1 0.64 None c.2588G.C p.Gly863Ala 1 1 0.64 None c.3113C.T p.Ala1038Val 1 1 0.64 None c.3899G.A p.Arg1300Gln 1 1 0.64 None c.5882G.A p.Gly1961Glu 1 1 0.64 None c.5908C.T p.Leu1970Phe 1 1 0.64 None c.6148G.C p.Val2050Leu 1 1 0.64 None c.6529G.A p.Asp2177Asn 2 2 1.28 None Total 10 Polymorphisms{ c.466A.G p.Ile156Val 5 5 3.2 None c.635G.A p.Arg212His 5 6 3.84 1 c.1268A.G p.His423Arg 43 48 30.7 5 c.1269C.T p.His423His 2 2 1.28 None IVS10+5delG 34 36 23 2 c.2828G.A p.Arg943Gln 1 1 0.64 None c.4203C.A p.Pro1401Pro 3 3 1.9 None IVS33+48C.T 59 75 48 16 c.5603A.T p.Asn1868Ile 4 4 2.5 None c.5682G.C p.Leu1894Leu 29 35 22.4 6 c.5814A.G p.Leu1938Leu 27 33 21.1 6 c.5843 C.T p.Pro1948Leu 9 10 6.4 1 c.5844A.G p.Pro1948Pro 27 32 20.5 5 c.6069C.T p.Ile2023Ile 11 12 7.7 1 c.6249C.T p.Ile2083Ile 12 14 8.9 2 c.6285T.C p.Asp2095Asp 24 26 16.6 2 c.6764G.T p.Ser2255Ile 12 13 8.3 1 *A total of 15 mutant alleles were detected. Login to comment
97 These Table 1 ABCA4 sequence variants identified in Spanish control population Mutant alleles Nucleotide change Amino acid change Number of cases Number of alleles Frequency (%) Homozygous individuals Mutations* c.661G.A p.Gly221Arg 1 1 0.64 None c.1140T.A p.Asn380Lys 1 1 0.64 None c.2588G.C p.Gly863Ala 1 1 0.64 None c.3113C.T p.Ala1038Val 1 1 0.64 None c.3899G.A p.Arg1300Gln 1 1 0.64 None c.5882G.A p.Gly1961Glu 1 1 0.64 None c.5908C.T p.Leu1970Phe 1 1 0.64 None c.6148G.C p.Val2050Leu 1 1 0.64 None c.6529G.A p.Asp2177Asn 2 2 1.28 None Total 10 Polymorphisms{ c.466A.G p.Ile156Val 5 5 3.2 None c.635G.A p.Arg212His 5 6 3.84 1 c.1268A.G p.His423Arg 43 48 30.7 5 c.1269C.T p.His423His 2 2 1.28 None IVS10+5delG 34 36 23 2 c.2828G.A p.Arg943Gln 1 1 0.64 None c.4203C.A p.Pro1401Pro 3 3 1.9 None IVS33+48C.T 59 75 48 16 c.5603A.T p.Asn1868Ile 4 4 2.5 None c.5682G.C p.Leu1894Leu 29 35 22.4 6 c.5814A.G p.Leu1938Leu 27 33 21.1 6 c.5843 C.T p.Pro1948Leu 9 10 6.4 1 c.5844A.G p.Pro1948Pro 27 32 20.5 5 c.6069C.T p.Ile2023Ile 11 12 7.7 1 c.6249C.T p.Ile2083Ile 12 14 8.9 2 c.6285T.C p.Asp2095Asp 24 26 16.6 2 c.6764G.T p.Ser2255Ile 12 13 8.3 1 *A total of 15 mutant alleles were detected. 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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111 Exon Nucleotide Change Effect STGD Families Frequency References IVS3 c.302+20C>T - 12 4.8% [6] IVS3 c.302+26A>G - 7,12,13,14 1.91% [6] 6 c.635G>A p.Arg212His 13,19 9.5% [15] IVS7 c.859+8T>C - 17 4.8% Present study 10 c.1268A>G p.His423Arg 2,4,5,6,10,11,12,13,14,18,19 53% [13] 10 c.1269C>T p.His423His 16 4.8% [13] IVS10 c.1356+5delG SPLICE 1,7,11,15,20 23.8% [13] IVS14 c.2161+47T>C - 18 4.8% Present study 19 c.2828G>A p.Arg943Gln 3,10,18,19 19.1% [5] IVS19 c.2919+34C>T - 12 4.8% Present study 20 c.2964T>C p.Leu988Leu 12 4.8% [6] IVS22 c.3326-19G>A - 2 4.8% Present study IVS33 c.4773+48C>T Splice 1,2,3,5,6,8,9,10,12,13,14,16,17,18,19,20 76.2% [13] 40 c.5603A>T p.Asn1868Ile 4,10,17 14.3% [6] 40 c.5682G>C p.Leu1894Leu 1,2,4,5,8,10,12,13,17,18 47.6% [6] 41 c.5814A>G p.Leu1938Leu 1,2,5,8,10,12,13,18 3.81% [6] 42 c.5843CA>TG/c.5843C>T p.Pro1948Leu 11 4.8% [14] 42 c.5844A>G p.Pro1948Pro 1,2,5,8,10,12,13 33.3% [14] 44 c.6069C>T p.Ile2023Ile 9,12,14,19 19.1% [6] 45 c.6249C>T p.Ile2083Ile 9,12,14,19 19.1% [5] 46 c.6285T>C p.Asp2095Asp 1,2,8,9,10,12,14,19 38.1% [14] IVS48 c.6769+21C>T SPLICE 1,10 9.5% [6] 49 c.6764G>T p.Ser2255Ile 1,9,14,19 19.1% [5] Several polymorphisms in exons and introns (IVS) throughout the entire ABCA4 gene were found in our study population. Login to comment
110 Exon Nucleotide Change Effect STGD Families Frequency References IVS3 c.302+20C>T - 12 4.8% [6] IVS3 c.302+26A>G - 7,12,13,14 1.91% [6] 6 c.635G>A p.Arg212His 13,19 9.5% [15] IVS7 c.859+8T>C - 17 4.8% Present study 10 c.1268A>G p.His423Arg 2,4,5,6,10,11,12,13,14,18,19 53% [13] 10 c.1269C>T p.His423His 16 4.8% [13] IVS10 c.1356+5delG SPLICE 1,7,11,15,20 23.8% [13] IVS14 c.2161+47T>C - 18 4.8% Present study 19 c.2828G>A p.Arg943Gln 3,10,18,19 19.1% [5] IVS19 c.2919+34C>T - 12 4.8% Present study 20 c.2964T>C p.Leu988Leu 12 4.8% [6] IVS22 c.3326-19G>A - 2 4.8% Present study IVS33 c.4773+48C>T Splice 1,2,3,5,6,8,9,10,12,13,14,16,17,18,19,20 76.2% [13] 40 c.5603A>T p.Asn1868Ile 4,10,17 14.3% [6] 40 c.5682G>C p.Leu1894Leu 1,2,4,5,8,10,12,13,17,18 47.6% [6] 41 c.5814A>G p.Leu1938Leu 1,2,5,8,10,12,13,18 3.81% [6] 42 c.5843CA>TG/c.5843C>T p.Pro1948Leu 11 4.8% [14] 42 c.5844A>G p.Pro1948Pro 1,2,5,8,10,12,13 33.3% [14] 44 c.6069C>T p.Ile2023Ile 9,12,14,19 19.1% [6] 45 c.6249C>T p.Ile2083Ile 9,12,14,19 19.1% [5] 46 c.6285T>C p.Asp2095Asp 1,2,8,9,10,12,14,19 38.1% [14] IVS48 c.6769+21C>T SPLICE 1,10 9.5% [6] 49 c.6764G>T p.Ser2255Ile 1,9,14,19 19.1% [5] Several polymorphisms in exons and introns (IVS) throughout the entire ABCA4 gene were found in our study population. Login to comment

[hide] Molecular testing for hereditary retinal disease a... Arch Ophthalmol. 2007 Feb;125(2):252-8. Downs K, Zacks DN, Caruso R, Karoukis AJ, Branham K, Yashar BM, Haimann MH, Trzupek K, Meltzer M, Blain D, Richards JE, Weleber RG, Heckenlively JR, Sieving PA, Ayyagari R
Molecular testing for hereditary retinal disease as part of clinical care.
Arch Ophthalmol. 2007 Feb;125(2):252-8., [PMID:17296903]

Abstract [show]
OBJECTIVE: To describe clinical molecular testing for hereditary retinal degenerations, highlighting results, interpretation, and patient education. METHODS: Mutation analysis of 8 retinal genes was performed by dideoxy sequencing. Pretest and posttest genetic counseling was offered to patients. The laboratory report listed results and provided individualized interpretation. RESULTS: A total of 350 tests were performed. The molecular basis of disease was determined in 133 of 266 diagnostic tests; the disease-causing mutations were not identified in the remaining 133 diagnostic tests. Predictive and carrier tests were requested for 9 and 75 nonsymptomatic patients with known familial mutations, respectively. CONCLUSIONS: Molecular testing can confirm a clinical diagnosis, identify carrier status, and confirm or rule out the presence of a familial mutation in nonsymptomatic at-risk relatives. Because causative mutations cannot be identified in all patients with retinal diseases, it is essential that patients are counseled before testing regarding the benefits and limitations of this emerging diagnostic tool. CLINICAL RELEVANCE: The molecular definition of the genetic basis of disease provides a unique adjunct to the clinical care of patients with hereditary retinal degenerations.

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116 5603A → T The sequence change alters the amino acid at position 1868, from asparagine to isoleucine. Login to comment

[hide] Denaturing HPLC profiling of the ABCA4 gene for re... Clin Chem. 2004 Aug;50(8):1336-43. Epub 2004 Jun 10. Stenirri S, Fermo I, Battistella S, Galbiati S, Soriani N, Paroni R, Manitto MP, Martina E, Brancato R, Allikmets R, Ferrari M, Cremonesi L
Denaturing HPLC profiling of the ABCA4 gene for reliable detection of allelic variations.
Clin Chem. 2004 Aug;50(8):1336-43. Epub 2004 Jun 10., [PMID:15192030]

Abstract [show]
BACKGROUND: Mutations in the retina-specific ABC transporter (ABCA4) gene have been associated with several forms of macular degenerations. Because the high complexity of the molecular genotype makes scanning of the ABCA4 gene cumbersome, we describe here the first use of denaturing HPLC (DHPLC) to screen for ABCA4 mutations. METHODS: Temperature conditions were designed for all 50 exons based on effective separation of 83 samples carrying 86 sequence variations and 19 mutagenized controls. For validation, samples from 23 previously characterized Stargardt patients were subjected to DHPLC profiling. Subsequently, samples from a cohort of 30 patients affected by various forms of macular degeneration were subjected to DHPLC scanning under the same conditions. RESULTS: DHPLC profiling not only identified all 132 sequence alterations previously detected by double-gradient denaturing gradient gel electrophoresis but also identified 5 sequence alterations that this approach had missed. Moreover, DHPLC scanning of an additional panel of 30 previously untested patients led to the identification of 26 different mutations and 29 polymorphisms, accounting for 203 sequence variations on 29 of the 30 patients screened. In total, the DHPLC approach allowed us to identify 16 mutations that had never been reported before. CONCLUSIONS: These results provide strong support for the use of DHPLC for molecular characterization of the ABCA4 gene.

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35 Exon Genotypesa Exon Genotypesa 1b M1V (1A>G) (11) 24 3523-28TϾC (12) R18W (52C>T) (11) 25 G1203D (3608G>A)b 3 250_251insCAAA (7) 27 R1300X (3898C>T) (12) N96K (288C>A) R1300Q (3899G>A) (11) 302 ϩ 26 GϾA (13) 28 P1380L (4139CϾT) (14) 4 P143L (428C>T) (10) P1401P (4203CϾA) (15) 5 R152Q (455G>A) (4) 4253 ϩ 43GϾA (12) 6 571-1GϾT (4) 29 4253 ϩ 13GϾA (12) R212H (635G>A) (16) 4354-38GϾA (4) C230S (688T>A) (12) 30a 4466 ϩ 3GϾA (4) 641delG (9) 30b C1490Y (4469G>A) (17) 10 1240-14CϾT (13) P1512R (4535C>G) (4) H423R (1268ϾG) (13) 31 T1526M (4577C>T) (14) 1357 ϩ 11delG (16) 33/34 A1598D (4793C>A) (4) H423H (1269CϾT) (13) 35 4947delC (14) 11 1387delTT (4) 5018 ؉ 2T>C (7) R500R (1500GϾA) (4) 39 H1838Y (5512C>T) (14) 12 L541P (1622T>C) (14) 40 N1868I (5603AϾT) (13) R572Q (1715G>A) (17) L1894L (5682GϾC) (15) 13 Y639X (1917C>G) (17) 5714 ؉ 5G>A C641S (1922G>C) (4) 41 L1938L (5814AϾG) (12) 14 R653C (1957C>T) (12) 42 5836-43CϾA W700X (2099G>A) (4) 5836-11GϾA (15) 3607 ϩ 49TϾC P1948I (5843CϾT) (15) 15 V767D (2300T>A) (7) P1948P (5844AϾG) (15) 16 W821R (2461T>A) (14) G1961E (5882G>A) (14) 17 2588-33CϾTb 43 L1970F (5908C>T) (11) G863A (2588G>C) (17) 44 6006-16AϾG (16) 18 2654-36CϾT (4) I2023I (6069CϾT) (14) T897I (2690C>T) (7) L2027F (6079C>T) (14) 19 R943Q (2828GϾA) (13) 45 V2050L (6148G>C) (14) Y954D (2860T>G) (4) 46 R2107H (6320G>A) (18) N965S (2894A>G) (14) 6386 ؉ 2G>C (10) 20 G978D (2933G>A) (4) 47 R2139W (6415C>T) (14) L988L (2964CϾT) (4) R2149L (6446G>T) (4) 21 E1022K (3064G>A) (4) C2150Y (6449G>A) (19) A1038V (3113C>T) (14) 48 D2177N (6529G>A) (17) G1050D (3149G>A) (4) L2241V (6721C>G) (12) 3211_3212insGT (14) 6729 ϩ 21CϾT (15) 22 E1087K (3259G>A) (14) 49 6730-3TϾC (15) R1098C (3292C>T) (12) S2255I (6764GϾT) (13) S1099P (3295T>C) (4) 6816 ϩ 28GϾC (4) R1108C (3322C>T) (14) R1129L (3386G>T) (17) a Bold indicates disease-causing mutations. Login to comment
34 Exon Genotypesa Exon Genotypesa 1b M1V (1A>G) (11) 24 3523-28Tb0e;C (12) R18W (52C>T) (11) 25 G1203D (3608G>A)b 3 250_251insCAAA (7) 27 R1300X (3898C>T) (12) N96K (288C>A) R1300Q (3899G>A) (11) 302 af9; 26 Gb0e;A (13) 28 P1380L (4139Cb0e;T) (14) 4 P143L (428C>T) (10) P1401P (4203Cb0e;A) (15) 5 R152Q (455G>A) (4) 4253 af9; 43Gb0e;A (12) 6 571-1Gb0e;T (4) 29 4253 af9; 13Gb0e;A (12) R212H (635G>A) (16) 4354-38Gb0e;A (4) C230S (688T>A) (12) 30a 4466 af9; 3Gb0e;A (4) 641delG (9) 30b C1490Y (4469G>A) (17) 10 1240-14Cb0e;T (13) P1512R (4535C>G) (4) H423R (1268b0e;G) (13) 31 T1526M (4577C>T) (14) 1357 af9; 11delG (16) 33/34 A1598D (4793C>A) (4) H423H (1269Cb0e;T) (13) 35 4947delC (14) 11 1387delTT (4) 5018 d19; 2T>C (7) R500R (1500Gb0e;A) (4) 39 H1838Y (5512C>T) (14) 12 L541P (1622T>C) (14) 40 N1868I (5603Ab0e;T) (13) R572Q (1715G>A) (17) L1894L (5682Gb0e;C) (15) 13 Y639X (1917C>G) (17) 5714 d19; 5G>A C641S (1922G>C) (4) 41 L1938L (5814Ab0e;G) (12) 14 R653C (1957C>T) (12) 42 5836-43Cb0e;A W700X (2099G>A) (4) 5836-11Gb0e;A (15) 3607 af9; 49Tb0e;C P1948I (5843Cb0e;T) (15) 15 V767D (2300T>A) (7) P1948P (5844Ab0e;G) (15) 16 W821R (2461T>A) (14) G1961E (5882G>A) (14) 17 2588-33Cb0e;Tb 43 L1970F (5908C>T) (11) G863A (2588G>C) (17) 44 6006-16Ab0e;G (16) 18 2654-36Cb0e;T (4) I2023I (6069Cb0e;T) (14) T897I (2690C>T) (7) L2027F (6079C>T) (14) 19 R943Q (2828Gb0e;A) (13) 45 V2050L (6148G>C) (14) Y954D (2860T>G) (4) 46 R2107H (6320G>A) (18) N965S (2894A>G) (14) 6386 d19; 2G>C (10) 20 G978D (2933G>A) (4) 47 R2139W (6415C>T) (14) L988L (2964Cb0e;T) (4) R2149L (6446G>T) (4) 21 E1022K (3064G>A) (4) C2150Y (6449G>A) (19) A1038V (3113C>T) (14) 48 D2177N (6529G>A) (17) G1050D (3149G>A) (4) L2241V (6721C>G) (12) 3211_3212insGT (14) 6729 af9; 21Cb0e;T (15) 22 E1087K (3259G>A) (14) 49 6730-3Tb0e;C (15) R1098C (3292C>T) (12) S2255I (6764Gb0e;T) (13) S1099P (3295T>C) (4) 6816 af9; 28Gb0e;C (4) R1108C (3322C>T) (14) R1129L (3386G>T) (17) a Bold indicates disease-causing mutations. Login to comment

[hide] Stargardt disease in a patient with retinoblastoma... Arch Ophthalmol. 2003 Nov;121(11):1643-6. Margalit E, Sunness JS, Green WR, Kelman SE, Schachat AP, Fiergang D, Allikmets R
Stargardt disease in a patient with retinoblastoma.
Arch Ophthalmol. 2003 Nov;121(11):1643-6., [PMID:14609928]

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53 Inthispatient,thechipdetected 5sequencevariants:H423R,P1401P, IVS33+48CϾT,N1868I,andL1894L, allofwhichareconsiderednonpatho- genic polymorphisms. Login to comment
52 Inthispatient,thechipdetected 5sequencevariants:H423R,P1401P, IVS33+48Cb0e;T,N1868I,andL1894L, allofwhichareconsiderednonpatho- genic polymorphisms. Login to comment

[hide] Genotyping microarray (gene chip) for the ABCR (AB... Hum Mutat. 2003 Nov;22(5):395-403. Jaakson K, Zernant J, Kulm M, Hutchinson A, Tonisson N, Glavac D, Ravnik-Glavac M, Hawlina M, Meltzer MR, Caruso RC, Testa F, Maugeri A, Hoyng CB, Gouras P, Simonelli F, Lewis RA, Lupski JR, Cremers FP, Allikmets R
Genotyping microarray (gene chip) for the ABCR (ABCA4) gene.
Hum Mutat. 2003 Nov;22(5):395-403., [PMID:14517951]

Abstract [show]
Genetic variation in the ABCR (ABCA4) gene has been associated with five distinct retinal phenotypes, including Stargardt disease/fundus flavimaculatus (STGD/FFM), cone-rod dystrophy (CRD), and age-related macular degeneration (AMD). Comparative genetic analyses of ABCR variation and diagnostics have been complicated by substantial allelic heterogeneity and by differences in screening methods. To overcome these limitations, we designed a genotyping microarray (gene chip) for ABCR that includes all approximately 400 disease-associated and other variants currently described, enabling simultaneous detection of all known ABCR variants. The ABCR genotyping microarray (the ABCR400 chip) was constructed by the arrayed primer extension (APEX) technology. Each sequence change in ABCR was included on the chip by synthesis and application of sequence-specific oligonucleotides. We validated the chip by screening 136 confirmed STGD patients and 96 healthy controls, each of whom we had analyzed previously by single strand conformation polymorphism (SSCP) technology and/or heteroduplex analysis. The microarray was >98% effective in determining the existing genetic variation and was comparable to direct sequencing in that it yielded many sequence changes undetected by SSCP. In STGD patient cohorts, the efficiency of the array to detect disease-associated alleles was between 54% and 78%, depending on the ethnic composition and degree of clinical and molecular characterization of a cohort. In addition, chip analysis suggested a high carrier frequency (up to 1:10) of ABCR variants in the general population. The ABCR genotyping microarray is a robust, cost-effective, and comprehensive screening tool for variation in one gene in which mutations are responsible for a substantial fraction of retinal disease. The ABCR chip is a prototype for the next generation of screening and diagnostic tools in ophthalmic genetics, bridging clinical and scientific research.

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88 Several common polymorphisms were also included, mainly from the coding region (R212H, H423R, R943Q, N1868I, P1948L, S2255I). Login to comment

[hide] Detailed analysis of allelic variation in the ABCA... Invest Ophthalmol Vis Sci. 2003 Jul;44(7):2868-75. Schmidt S, Postel EA, Agarwal A, Allen IC Jr, Walters SN, De la Paz MA, Scott WK, Haines JL, Pericak-Vance MA, Gilbert JR
Detailed analysis of allelic variation in the ABCA4 gene in age-related maculopathy.
Invest Ophthalmol Vis Sci. 2003 Jul;44(7):2868-75., [PMID:12824224]

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PURPOSE: Age-related maculopathy (ARM) is one of the most common causes of blindness in older adults worldwide. Sequence variants in a gene coding for a retina-specific ATP-binding cassette (ABCA4) transporter protein, which is responsible for a phenotypically similar Mendelian form of retinal disease, were proposed to increase the risk of ARM. To examine the potential relationship of ABCA4 sequence variation and ARM risk in an independent data set, a clinically well-characterized population of 165 multiplex patients with ARM from 70 families, 33 unaffected relatives, and 59 unrelated control subjects with confirmed absence of ARM was screened for variants in any of the 50 exons and exon-intron boundaries of this gene. METHODS: A combination of denaturing high-performance liquid chromatography (DHPLC) and bidirectional sequencing was used to detect ABCA4 sequence variants. The data set was analyzed with both case-control and family-based association analysis methods. RESULTS: No evidence was found of significantly different allele frequencies of ABCA4 sequence variants in patients compared with control subjects, and no evidence for association or cosegregation with disease in family-based analyses. CONCLUSIONS: This study confirmed the very high degree of ABCA4 sequence polymorphism in the general population, which makes the detection of potential disease-associated alleles particularly challenging. While this study does not definitively exclude ABCA4 from contributing to a small or moderate fraction of ARM, it adds to the body of evidence suggesting that ABCA4 is not a major susceptibility gene for this disorder.

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123 Polymorphisms and Rare Sequence Variants in Exons of the ABCA4 Gene Exon Nucleotide Change Effect Allele Frequency* P† P§ Referenceሻ Independent ARM (n ‫؍‬ 140) All ARM (n ‫؍‬ 330) Control Subjects (n ‫؍‬ 118) 6 589G3C Asp197Asn 0.000 0.000 0.009 0.46 0.12 - 6 635G3A Arg212His 0.030 0.026 0.000 0.13 0.11 W, R 10 1268A3G His423Arg 0.394 0.371 0.427 0.62‡ 0.34 W, R 10 1269C3T His423His(syn) 0.033 0.039 0.031 1.0 0.74 W 18 2701A3G Thr901Ala 0.000 0.003 0.000 NA 0.58 W, R 23 3495C3T Asn1165Asn(syn) 0.000 0.003 0.000 NA 0.75 - 30 4469G3A Cys1490Tyr 0.007 0.003 0.000 1.0 0.59 W 37 5206T3C Ser1736Pro 0.009 0.008 0.000 1.0 0.44 W 40 5603T3A Asn1868Ile 0.100 0.102 0.054 0.29 0.18 W 40 5682G3C Leu1894Leu(syn) 0.293 0.272 0.298 1.0 0.64 W 41 5814A3G Leu1938Leu(syn) 0.160 0.169 0.218 0.33 0.38 W 42 5843C3T Pro1948Leu 0.052 0.038 0.054 1.0 0.50 W 42 5844A3G Pro1948Pro(syn) 0.199 0.192 0.205 1.0 0.77 W 44 6069C3T Ile2023Ile(syn) 0.040 0.050 0.044 1.0 0.82 W 44 6079C3T Leu2027Phe 0.000 0.000 0.009 0.48 0.13 W * Actual n (number of chromosomes) varies, as frequencies were calculated relative to nonmissing data only. Login to comment

[hide] Kjellin's syndrome: fundus autofluorescence, angio... Ophthalmology. 2002 Aug;109(8):1484-91. Frisch IB, Haag P, Steffen H, Weber BH, Holz FG
Kjellin's syndrome: fundus autofluorescence, angiographic, and electrophysiologic findings.
Ophthalmology. 2002 Aug;109(8):1484-91., [PMID:12153800]

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OBJECTIVE: Syndromes with genetically determined retinal diseases and concurrent multiple neurologic abnormalities are rare. Kjellin described an autosomal recessive entity with spastic paraplegia, mental retardation, amyotrophia, and macular dystrophy. We sought to further characterize the retinal phenotype and to contrast fundus changes and the genotype to Stargardt's disease in a young patient with progressive Kjellin's syndrome. DESIGN: Observational case report and family genetic study. PATIENTS: One affected and 11 unaffected members of a family with Kjellin's syndrome were investigated. METHODS: Complete ophthalmologic and neurologic examinations were performed, including electrophysiologic evaluation, color vision assessment, fundus autofluorescence, and fluorescence angiography. To investigate a possible role of the ABCA4 gene in the etiology of the macular changes, the entire 50 coding exons, including flanking intronic sequences of the patient, were analyzed by direct sequencing. MAIN OUTCOME MEASURES: The patient was evaluated for her symptoms, retinal function, fundus autofluorescence, angiography, and mutations in the ABCA4 gene. RESULTS: A 27-year-old female patient initially was seen with trembling of her right hand. Subsequently, progressive paraspasticity occurred, and a diagnostic workup revealed mild mental retardation. Biomicroscopy disclosed symmetric multiple round yellowish flecks at the level of the retinal pigment epithelium scattered at the posterior pole, which showed increased intrinsic fluorescence in the center, with a halo of reduced autofluorescence. Multifocal electroretinography elicited abnormal responses in the macular area in the presence of normal Ganzfeld electroretinography recordings. In gene mapping, several common variants were identified, although none seem to be associated with the disease features. CONCLUSIONS: Macular changes in Kjellin's syndrome share phenotypic characteristics with Stargardt's disease, although there are differences with regard to appearance, distribution, angiographic, and autofluorescence behavior of the retinal flecks. Ophthalmologic examination is prudent in patients with similar neurologic deficits, because it is essential for the diagnosis and because visual symptoms may be absent even in the presence of obvious and widespread retinal manifestations. The abnormal gene product in Kjellin's syndrome seems to cause progressive dysfunction in various neuronal tissues but seems to be distinct from the major defect underlying the Stargardt's disease phenotype.

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69 intragenic polymorphisms 5603AϾT (N1868I), 5682GϾC (L1894I), and IVS28 ϩ 43GϾA (Fig 7). Login to comment
71 We therefore decided to use polymerase chain reaction amplification and directly sequence all coding exons and flanking intronic sequences of the patient`s ABCA4 gene by using primer sequences and polymerase chain reaction conditions as described previously in Rivera et al.12 Besides the N1868I and IVS28 ϩ 43GϾA polymorphisms, the patient was also heterozygous for DNA variants IVS6-32TϾC, 3331AϾC (R1111R), 5814AϾG (L1938L), IVS43-16GϾA, and 6285TϾC (D2095D). Login to comment

[hide] The ABCA4 2588G>C Stargardt mutation: single origi... Eur J Hum Genet. 2002 Mar;10(3):197-203. Maugeri A, Flothmann K, Hemmrich N, Ingvast S, Jorge P, Paloma E, Patel R, Rozet JM, Tammur J, Testa F, Balcells S, Bird AC, Brunner HG, Hoyng CB, Metspalu A, Simonelli F, Allikmets R, Bhattacharya SS, D'Urso M, Gonzalez-Duarte R, Kaplan J, te Meerman GJ, Santos R, Schwartz M, Van Camp G, Wadelius C, Weber BH, Cremers FP
The ABCA4 2588G>C Stargardt mutation: single origin and increasing frequency from South-West to North-East Europe.
Eur J Hum Genet. 2002 Mar;10(3):197-203., [PMID:11973624]

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Inherited retinal dystrophies represent the most important cause of vision impairment in adolescence, affecting approximately 1 out of 3000 individuals. Mutations of the photoreceptor-specific gene ABCA4 (ABCR) are a common cause of retinal dystrophy. A number of mutations have been repeatedly reported for this gene, notably the 2588G>C mutation which is frequent in both patients and controls. Here we ascertained the frequency of the 2588G>C mutation in a total of 2343 unrelated random control individuals from 11 European countries and 241 control individuals from the US, as well as in 614 patients with STGD both from Europe and the US. We found an overall carrier frequency of 1 out of 54 in Europe, compared with 1 out of 121 in the US, confirming that the 2588G>C ABCA4 mutation is one of the most frequent autosomal recessive mutations in the European population. Carrier frequencies show an increasing gradient in Europe from South-West to North-East. The lowest carrier frequency, 0 out of 199 (0%), was found in Portugal; the highest, 11 out of 197 (5.5%), was found in Sweden. Haplotype analysis in 16 families segregating the 2588G>C mutation showed four intragenic polymorphisms invariably present in all 16 disease chromosomes and sharing of the same allele for several markers flanking the ABCA4 locus in most of the disease chromosomes. These results indicate a single origin of the 2588G>C mutation which, to our best estimate, occurred between 2400 and 3000 years ago.

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41 (N1868I) and 5682G4C (L1894L), invariably present in all 16 disease chromosomes, whether from the Netherlands, Germany or Sweden (Figure 2). Login to comment
89 Interestingly, functional studies23 showed a small but reproducible decrease in ATPase activity, relative to wild type, for the N1868I (5603A4T) protein. Login to comment
88 Interestingly, functional studies23 showed a small but reproducible decrease in ATPase activity, relative to wild type, for the N1868I (5603A4T) protein. Login to comment

[hide] Null missense ABCR (ABCA4) mutations in a family w... Invest Ophthalmol Vis Sci. 2001 Nov;42(12):2757-61. Shroyer NF, Lewis RA, Yatsenko AN, Lupski JR
Null missense ABCR (ABCA4) mutations in a family with stargardt disease and retinitis pigmentosa.
Invest Ophthalmol Vis Sci. 2001 Nov;42(12):2757-61., [PMID:11687513]

Abstract [show]
PURPOSE: To determine the type of ABCR mutations that segregate in a family that manifests both Stargardt disease (STGD) and retinitis pigmentosa (RP), and the functional consequences of the underlying mutations. METHODS: Direct sequencing of all 50 exons and flanking intronic regions of ABCR was performed for the STGD- and RP-affected relatives. RNA hybridization, Western blot analysis, and azido-adenosine triphosphate (ATP) labeling was used to determine the effect of disease-associated ABCR mutations in an in vitro assay system. RESULTS: Compound heterozygous missense mutations were identified in patients with STGD and RP. STGD-affected individual AR682-03 was compound heterozygous for the mutation 2588G-->C and a complex allele, [W1408R; R1640W]. RP-affected individuals AR682-04 and-05 were compound heterozygous for the complex allele [W1408R; R1640W] and the missense mutation V767D. Functional analysis of the mutation V767D by Western blot and ATP binding revealed a severe reduction in protein expression. In vitro analysis of ABCR protein with the mutations W1408R and R1640W showed a moderate effect of these individual mutations on expression and ATP-binding; the complex allele [W1408R; R1640W] caused a severe reduction in protein expression. CONCLUSIONS: These data reveal that missense ABCR mutations may be associated with RP. Functional analysis reveals that the RP-associated missense ABCR mutations are likely to be functionally null. These studies of the complex allele W1408R; R1640W suggest a synergistic effect of the individual mutations. These data are congruent with a model in which RP is associated with homozygous null mutations and with the notion that severity of retinal disease is inversely related to residual ABCR activity.

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102 ABCR Alterations in Patients with Stargardt Disease and Retinitis Pigmentosa Exon Nucleotide Amino Acid AR682-03 AR682-04 3 302ϩ26 A/A A/G 10 1268G 3 A H423R A/A A/G 1356ϩ11delG 6G/6G 6G/7G 15 2300T 3 A V767D T/T T/A 17 2588G 3 C G863A G/C G/G 19 2828G 3 A R943Q G/A G/G 24 3523-30 A/T A/T 28 4203C 3 A P1401P C/A C/C 4222T 3 C W1408R C/T C/T 33 4667ϩ48 C/T T/T 35 4918C 3 T R1640W C/T C/T 40 5585-70 C/T T/T 5603A 3 T N1868I A/T A/A 5682G 3 C L1894L G/C G/G Mutations are indicated in bold. Login to comment
101 ABCR Alterations in Patients with Stargardt Disease and Retinitis Pigmentosa Exon Nucleotide Amino Acid AR682-03 AR682-04 3 302af9;26 A/A A/G 10 1268G 3 A H423R A/A A/G 1356af9;11delG 6G/6G 6G/7G 15 2300T 3 A V767D T/T T/A 17 2588G 3 C G863A G/C G/G 19 2828G 3 A R943Q G/A G/G 24 3523-30 A/T A/T 28 4203C 3 A P1401P C/A C/C 4222T 3 C W1408R C/T C/T 33 4667af9;48 C/T T/T 35 4918C 3 T R1640W C/T C/T 40 5585-70 C/T T/T 5603A 3 T N1868I A/T A/A 5682G 3 C L1894L G/C G/G Mutations are indicated in bold. Login to comment

[hide] Different clinical expressions in two families wit... Acta Ophthalmol Scand. 2001 Oct;79(5):524-30. Eksandh L, Ekstrom U, Abrahamson M, Bauer B, Andreasson S
Different clinical expressions in two families with Stargardt's macular dystrophy (STGD1).
Acta Ophthalmol Scand. 2001 Oct;79(5):524-30., [PMID:11594993]

Abstract [show]
PURPOSE: To describe the clinical expressions, with emphasis on electrophysiological examinations, in two Swedish families with Stargardt's macular dystrophy (STGD1). METHODS: Two pairs of siblings with STGD1, for whom diagnosis had been confirmed by genetic linkage to the ABCA4 gene region, were examined regarding visual acuity, kinetic perimetry, fundus photography, full-field ERG and multifocal ERG (MERG). Possible disease-causing mutations were screened for by DNA sequencing of selected regions of the ABCA4 gene. RESULTS: All STGD1 patients had visual acuity 0.07-0.1. The two families presented different fundus appearances, MERGs and implicit times on 30 Hz flicker white light full-field ERGs. Genetic analysis revealed one unique sequence variation in exon 19 of the ABCA4 gene, in one allele from the patients of one of the families. This point mutation causes the amino acid substitution T972N in the ABCR protein. CONCLUSION: Two pairs of siblings with STGD1 presented two different expressions of the disease regarding the distribution of the retinal dysfunction. One possible molecular explanation to the different clinical expressions may be the T972N substitution present in the ABCR protein in one of the STGD1 families investigated.

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96 Of these, the two in exon 40 (5603A»T causing the substitution N1868I and the sense mutation 5682G»C in the codon for Leu1894) could be excluded as disease-associated since they were found in both alleles of the gene from the asymptomatic mother in one of the families. Login to comment
113 Ex 40 5603A-ϾT N1868I A/A A/A A/A A/A A/T A/T A/A T/T Asympt. mother homozygous. Login to comment

[hide] Mutational scanning of the ABCR gene with double-g... Hum Genet. 2001 Sep;109(3):326-38. Fumagalli A, Ferrari M, Soriani N, Gessi A, Foglieni B, Martina E, Manitto MP, Brancato R, Dean M, Allikmets R, Cremonesi L
Mutational scanning of the ABCR gene with double-gradient denaturing-gradient gel electrophoresis (DG-DGGE) in Italian Stargardt disease patients.
Hum Genet. 2001 Sep;109(3):326-38., [PMID:11702214]

Abstract [show]
Mutations in the retina-specific ABC transporter (ABCR) gene are responsible for autosomal recessive Stargardt disease (arSTGD). Mutation detection efficiency in ABCR in arSTGD patients ranges between 30% and 66% in previously published studies, because of high allelic heterogeneity and technical limitations of the employed methods. Conditions were developed to screen the ABCR gene by double-gradient denaturing-gradient gel electrophoresis. The efficacy of this method was evaluated by analysis of DNA samples with previously characterized ABCR mutations. This approach was applied to mutation detection in 44 Italian arSTGD patients corresponding to 36 independent genomes, in order to assess the nature and frequency of the ABCR mutations in this ethnic group. In 34 of 36 (94.4%) STGD patients, 37 sequence changes were identified, including 26 missense, six frameshift, three splicing, and two nonsense variations. Among these, 20 had not been previously described. Several polymorphisms were detected in affected individuals and in matched controls. Our findings extend the spectrum of mutations identified in STGD patients and suggest the existence of a subset of molecular defects specific to the Italian population. The identification of at least two disease-associated mutations in four healthy control individuals indicates a higher than expected carrier frequency of variant ABCR alleles in the general population. Genotype-phenotype analysis in our series showed a possible correlation between the nature and location of some mutations and specific ophthalmoscopic features of STGD disease.

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37 DNA samples (n=22) carrying previously identified mutations in the ABCR gene were employed as controls for evaluating the efficacy of the DG-DGGE approach in detecting sequence variations R572Q (Lewis et al. 1999), Y639X (Lewis et al. 1999), G863A (Lewis et al. 1999; Maugeri et al. 1999), A1038V (Rozet et al. 1998), T1019M (Rozet et al. 1998), 3211insGT (Lewis et al. 1999), P1380L (Lewis et al. 1999), H1406Y (Lewis et al. 1999), 4947delC (Lewis et al. 1999), H1838Y (Lewis et al. 1999), 5714+5G→A (Cremers et al. 1998), N1868I (De La Paz et al. 1999), L1938L (Rivera et al. 2000), G1961E (Allikmets et al. 1997a, 1997b), L1970F (Lewis et al. 1999), L2027F (Nasonkin et al. 1998), V2050L (Lewis et al. 1999), E2131K (Lewis et al. 1999), R2139W (Lewis et al. 1999), 6709insG (Lewis et al. 1999), D2177N (Allikmets et al. 1997a, 1997b), 2181del12 (Lewis et al. 1999). Login to comment

[hide] Mutations in ABCR (ABCA4) in patients with Stargar... Invest Ophthalmol Vis Sci. 2001 Sep;42(10):2229-36. Briggs CE, Rucinski D, Rosenfeld PJ, Hirose T, Berson EL, Dryja TP
Mutations in ABCR (ABCA4) in patients with Stargardt macular degeneration or cone-rod degeneration.
Invest Ophthalmol Vis Sci. 2001 Sep;42(10):2229-36., [PMID:11527935]

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PURPOSE: To determine the spectrum of ABCR mutations associated with Stargardt macular degeneration and cone-rod degeneration (CRD). METHODS: One hundred eighteen unrelated patients with recessive Stargardt macular degeneration and eight with recessive CRD were screened for mutations in ABCR (ABCA4) by single-strand conformation polymorphism analysis. Variants were characterized by direct genomic sequencing. Segregation analysis was performed on the families of 20 patients in whom at least two or more likely pathogenic sequence changes were identified. RESULTS: The authors found 77 sequence changes likely to be pathogenic: 21 null mutations (15 novel), 55 missense changes (26 novel), and one deletion of a consensus glycosylation site (also novel). Fifty-two patients with Stargardt macular degeneration (44% of those screened) and five with CRD each had two of these sequence changes or were homozygous for one of them. Segregation analyses in the families of 19 of these patients were informative and revealed that the index cases and all available affected siblings were compound heterozygotes or homozygotes. The authors found one instance of an apparently de novo mutation, Ile824Thr, in a patient. Thirty-seven (31%) of the 118 patients with Stargardt disease and one with CRD had only one likely pathogenic sequence change. Twenty-nine patients with Stargardt disease (25%) and two with CRD had no identified sequence changes. CONCLUSIONS: This report of 42 novel mutations brings the growing number of identified likely pathogenic sequence changes in ABCR to approximately 250.

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65 Four missense changes, Arg212His, His423Arg, Arg943Gln, and Pro1948Leu, were found at approximately equal frequency among patients and normal control subjects (P Ͼ 0.05 by Fisher`s two-tailed analysis) and were thus categorized as nonpathogenic polymorphisms. Login to comment
66 Asn1868Ile was less frequent in patients with Stargardt disease than in control subjects (42/252 patient alleles and 50/170 control alleles; P ϭ 0.002 by Fisher`s two-tailed analysis) and was therefore considered nonpathogenic. Login to comment

[hide] Analysis of the ABCR (ABCA4) gene in 4-aminoquinol... Am J Ophthalmol. 2001 Jun;131(6):761-6. Shroyer NF, Lewis RA, Lupski JR
Analysis of the ABCR (ABCA4) gene in 4-aminoquinoline retinopathy: is retinal toxicity by chloroquine and hydroxychloroquine related to Stargardt disease?
Am J Ophthalmol. 2001 Jun;131(6):761-6., [PMID:11384574]

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PURPOSE: To determine if mutations in ABCR (ABCA4) are associated with chloroquine/hydroxychloroquine retinopathy. METHODS: DNA from eight patients with chloroquine or hydroxychloroquine retinopathy was studied. Controls were 80 individuals over age 65 years with normal retinal examinations. Ophthalmoscopy, color vision testing, visual fields, retinal photography, and fluorescein angiography were performed on the eight patients. Direct DNA sequencing of the exons and flanking intronic regions of the ABCR gene was completed for all patients. RESULTS: Clinical evaluation confirmed the diagnosis of chloroquine/hydroxychloroquine retinopathy and excluded Stargardt disease in each patient. Two patients had heterozygous ABCR missense mutations previously associated with Stargardt disease. None of the controls had these missense mutations. Three other patients had other missense polymorphisms. CONCLUSIONS: Some individuals who have ABCR mutations may be predisposed to develop retinal toxicity when exposed to chloroquine/hydroxychloroquine. We urge further study of a larger cohort of patients with chloroquine/hydroxychloroquine retinopathy.

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60 ABCR Coding Alterations in Patients With Chloroquine and Hydroxychloroquine Retinopathy Exon Nucleotide* Amino Acid* Patient Number 1 2 3 4 5 6 7 8 6 635 Arg212His G/G G/G G/G G/G G/G G/G A/G G/G 10 1268 His423Arg A/A A/A A/A G/G A/A A/A A/A A/A 1269 His423His C/C C/C C/C C/C C/C C/T C/T C/C 20 2964 Leu988Leu C/C C/C C/C C/C C/C C/C C/T C/C 23 3385 Arg1129Cys† C/C C/C C/T† C/C C/C C/C C/C C/C 24 3602 Leu1201Arg† T/T T/T T/T T/T T/T T/T T/G† T/T 28 4203 Pro1401Pro C/C C/C C/C C/A C/A C/C C/C C/C 40 5603 Asn1868Ile A/A A/A A/A A/T A/T A/A A/A A/A 5682 Leu1894Leu G/G G/C G/C G/C G/C G/G C/C G/G 41 5814 Leu1938Leu A/A A/G A/G A/A A/A A/A G/G A/A 42 5844 Pro1948Pro A/A A/G A/G A/A A/A A/A G/G A/A 44 6069 Ile2023Ile C/C C/C C/C C/C C/C C/T C/C C/T 45 6249 Ile2083Ile C/C C/C C/C C/C C/C C/T C/C C/T 46 6285 Asp2095Asp T/T T/T T/T T/T T/T T/T C/C T/C 6320 Arg2107His† G/G G/G G/G G/G G/G G/G A/A† G/G 49 6764 Ser2255Ile G/G G/G G/G G/G G/G G/G G/T G/T *Standard amino acid and nucleotide abbreviations are used. Login to comment
63 Subject 4 is also heterozygous for the transversion 5603A3T, which by conceptual translation results in the substitution of Ile for Asn (Asn1868Ile). Login to comment
64 Subject 5 is heterozygous for the substitution Asn1868Ile, and subject 8 is heterozygous for the substitution Ser2255Ile. Login to comment

[hide] An analysis of allelic variation in the ABCA4 gene... Invest Ophthalmol Vis Sci. 2001 May;42(6):1179-89. Webster AR, Heon E, Lotery AJ, Vandenburgh K, Casavant TL, Oh KT, Beck G, Fishman GA, Lam BL, Levin A, Heckenlively JR, Jacobson SG, Weleber RG, Sheffield VC, Stone EM
An analysis of allelic variation in the ABCA4 gene.
Invest Ophthalmol Vis Sci. 2001 May;42(6):1179-89., [PMID:11328725]

Abstract [show]
PURPOSE: To assess the allelic variation of the ATP-binding transporter protein (ABCA4). METHODS: A combination of single-strand conformation polymorphism (SSCP) and automated DNA sequencing was used to systematically screen this gene for sequence variations in 374 unrelated probands with a clinical diagnosis of Stargardt disease, 182 patients with age-related macular degeneration (AMD), and 96 normal subjects. RESULTS: There was no significant difference in the proportion of any single variant or class of variant between the control and AMD groups. In contrast, truncating variants, amino acid substitutions, synonymous codon changes, and intronic variants were significantly enriched in patients with Stargardt disease when compared with their presence in subjects without Stargardt disease (Kruskal-Wallis P < 0.0001 for each variant group). Overall, there were 2480 instances of 213 different variants in the ABCA4 gene, including 589 instances of 97 amino acid substitutions, and 45 instances of 33 truncating variants. CONCLUSIONS: Of the 97 amino acid substitutions, 11 occurred at a frequency that made them unlikely to be high-penetrance recessive disease-causing variants (HPRDCV). After accounting for variants in cis, one or more changes that were compatible with HPRDCV were found on 35% of all Stargardt-associated alleles overall. The nucleotide diversity of the ABCA4 coding region, a collective measure of the number and prevalence of polymorphic sites in a region of DNA, was found to be 1.28, a value that is 9 to 400 times greater than that of two other macular disease genes that were examined in a similar fashion (VMD2 and EFEMP1).

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102 Thirty-Three Truncated and 98 Amino Acid-Changing Variants in the ABCA4 Gene Exon Nucleotide Change Effect (A) (B) AMD (n ‫؍‬ 182) Control (n ‫؍‬ 96) STGD (n ‫؍‬ 374) Allele Prevalence 2 106delT FS NS 0 0 1 Ͻ0.01 2 160 ϩ 1g 3 a Splice site NS 0 0 1 Ͻ0.01 3 161G 3 A Cys54Tyr NS 0 0 6 Ͻ0.01 3 179C 3 T Ala60Val NS 0 0 2 Ͻ0.01 3 194G 3 A Gly65Glu NS 0 0 2 Ͻ0.01 3 223T 3 G Cys75Gly NS 0 0 2 Ͻ0.01 3 247delCAAA FS NS 0 0 2 Ͻ0.01 3 298C 3 T Ser100Pro NS 0 0 1 Ͻ0.01 5 454C 3 T Arg152Stop NS 0 0 2 Ͻ0.01 6 574G 3 A Ala192Thr NS 0 0 1 Ͻ0.01 6 618C 3 G Ser206Arg NS 0 0 3 Ͻ0.01 6 634C 3 T Arg212Cys 0.02 Yes 0 0 7 0.01 6 635G 3 A Arg212His NS 2 2 6 0.01 6 658C 3 T Arg220Cys NS 0 0 2 Ͻ0.01 6 661delG FS NS 0 0 1 Ͻ0.01 666delAAAGACGGTGC 6 GC FS NS 0 0 1 Ͻ0.01 6 746A 3 C Asp249Gly NS 0 0 1 Ͻ0.01 8 899C 3 A Thr300Asn NS 0 0 1 Ͻ0.01 8 997C 3 T Arg333Trp NS 0 0 1 Ͻ0.01 9 1140T 3 A Asn380Lys NS 0 0 1 Ͻ0.01 9 1222C 3 T Arg408Stop NS 0 0 1 Ͻ0.01 10 1268A 3 G His423Arg NS 1 0 7 0.01 10 1335C 3 G Ser445Arg NS 0 0 1 Ͻ0.01 10 1344delG FS NS 0 0 1 Ͻ0.01 11 1411G 3 A Glu471Lys NS 0 0 3 Ͻ0.01 11 1513delATCAC FS NS 0 0 1 Ͻ0.01 12 1622T 3 C Leu541Pro 0.001 Yes 0 0 11 0.01 13 1804C 3 T Arg602Trp NS 0 0 3 Ͻ0.01 13 1805G 3 A Arg602Gln NS 0 0 1 Ͻ0.01 13 1819G 3 T Gly607Trp NS 0 0 1 Ͻ0.01 13 1823T 3 A Phe608Ile NS 0 0 1 Ͻ0.01 13 1927G 3 A Val643Met NS 0 0 1 Ͻ0.01 14 1989G 3 T Trp663Stop NS 0 0 1 Ͻ0.01 14 2005delAT FS NS 0 0 3 Ͻ0.01 14 2041C 3 T Arg681Stop NS 0 0 2 Ͻ0.01 14 2147C 3 T Thr716Met NS 0 0 1 Ͻ0.01 15 2291G 3 A Cys764Tyr NS 0 0 1 Ͻ0.01 15 2294G 3 A Ser765Asn NS 0 0 1 Ͻ0.01 15 2300T 3 A Val767Asp NS 0 0 2 Ͻ0.01 16 2385del16bp FS NS 0 0 1 Ͻ0.01 16 2453G 3 A Gly818Glu NS 0 0 1 Ͻ0.01 16 2461T 3 A Trp821Arg NS 0 0 1 Ͻ0.01 16 2546T 3 C Val849Ala NS 0 0 4 Ͻ0.01 16 2552G 3 A Gly851Asp NS 0 0 1 Ͻ0.01 16 2560G 3 A Ala854Thr NS 0 0 1 Ͻ0.01 17 2588G 3 C Gly863Ala 0.0006 No 2 2 28 0.02 17 2617T 3 C Phe873Leu NS 0 0 1 Ͻ0.01 18 2690C 3 T Thr897Ile NS 0 0 1 Ͻ0.01 18 2701A 3 G Thr901Ala NS 0 1 0 Ͻ0.01 18 2703A 3 G Thr901Arg NS 0 0 2 Ͻ0.01 19 2828G 3 A Arg943Gln NS 20 13 37 0.05 19 2883delC FS NS 0 0 1 Ͻ0.01 20 2894A 3 G Asn965Ser NS 0 0 3 Ͻ0.01 19 2912C 3 A Thr971Asn NS 0 0 1 Ͻ0.01 19 2915C 3 A Thr972Asn NS 0 0 1 Ͻ0.01 20 2920T 3 C Ser974Pro NS 0 0 1 Ͻ0.01 20 2966T 3 C Val989Ala NS 0 0 2 Ͻ0.01 20 2977del8bp FS NS 0 0 1 Ͻ0.01 20 3041T 3 G Leu1014Arg NS 0 0 1 Ͻ0.01 21 3055A 3 G Thr1019Ala NS 0 0 1 Ͻ0.01 21 3064G 3 A Glu1022Lys NS 0 0 1 Ͻ0.01 21 3091A 3 G Lys1031Glu NS 0 0 1 Ͻ0.01 21 3113G 3 T Ala1038Val 0.001 Yes 1 0 17 0.01 22 3205insAA FS NS 0 0 1 Ͻ0.01 22 3261G 3 A Glu1087Lys NS 0 0 2 Ͻ0.01 22 3322C 3 T Arg1108Cys 0.04 Yes 0 0 6 Ͻ0.01 22 3323G 3 A Arg1108His NS 0 0 1 Ͻ0.01 23 3364G 3 A Glu1122Lys NS 0 0 1 Ͻ0.01 (continues) Exon Nucleotide Change Effect (A) (B) AMD (n ‫؍‬ 182) Control (n ‫؍‬ 96) STGD (n ‫؍‬ 374) Allele Prevalence 23 3386G 3 T Arg1129Leu NS 0 0 3 Ͻ0.01 24 3531C 3 A Cys1158Stop NS 0 0 1 Ͻ0.01 25 3749T 3 C Leu1250Pro NS 0 0 1 Ͻ0.01 26 3835delGATTCT FS NS 0 0 1 Ͻ0.01 27 3940C 3 A Pro1314Thr NS 0 1 0 Ͻ0.01 28 4139C 3 T Pro1380Leu 0.001 Yes 0 0 10 0.01 28 4222T 3 C Trp1408Arg NS 0 0 2 Ͻ0.01 28 4223G 3 T Trp1408Leu NS 0 0 2 Ͻ0.01 28 4234C 3 T Gln1412stop NS 0 0 1 Ͻ0.01 29 4297G 3 A Val1433Ile NS 1 0 0 Ͻ0.01 29 4319T 3 C Phe1440Ser NS 0 0 1 Ͻ0.01 30 4353 - 1g 3 t Splice site NS 0 0 1 Ͻ0.01 30 4457C 3 T Pro1486Leu NS 0 0 1 Ͻ0.01 30 4462T 3 C Cys1488Arg NS 0 0 3 Ͻ0.01 30 4463G 3 T Cys1488Phe NS 0 0 2 Ͻ0.01 30 4469G 3 A Cys1490Tyr NS 0 0 3 Ͻ0.01 30 4531insC FS NS 0 0 2 Ͻ0.01 32 4538A 3 G Gln1513Arg NS 0 0 1 Ͻ0.01 30 4539 ϩ 1g 3 t Splice site NS 0 0 1 Ͻ0.01 31 4574T 3 C Leu1525Pro NS 0 0 1 Ͻ0.01 33 4733delGTTT FS NS 0 0 1 Ͻ0.01 4859delATAACAinsTCC 35 T FS NS 0 0 1 Ͻ0.01 36 4909G 3 A Ala1637Thr NS 0 0 1 Ͻ0.01 35 4918C 3 T Arg1640Trp NS 0 0 1 Ͻ0.01 35 4919G 3 A Arg1640Gln NS 0 0 1 Ͻ0.01 35 4954T 3 G Tyr1652Asp NS 0 0 1 Ͻ0.01 36 5077G 3 A Val1693Ile NS 0 0 1 Ͻ0.01 36 5186T 3 C Leu1729Pro NS 0 0 2 Ͻ0.01 36 5206T 3 C Ser1736Pro NS 0 0 1 Ͻ0.01 36 5212del11bp FS NS 0 0 1 Ͻ0.01 37 5225delTGGTGGTGGGC FS NS 0 0 1 Ͻ0.01 del LPA 37 5278del9bp 1760 NS 0 0 1 Ͻ0.01 37 5288delG FS NS 0 0 1 Ͻ0.01 38 5395A 3 G Asn1799Asp NS 0 0 1 Ͻ0.01 38 5451T 3 G Asp1817Glu NS 1 0 4 Ͻ0.01 39 5584 ϩ 5g 3 a Splice site 0.02 Yes 0 0 6 Ͻ0.01 40 5603A 3 T Asn1868Ile 0.0006 No 20 7 79 0.08 40 5651T 3 A Val1884GLu NS 0 0 1 Ͻ0.01 40 5657G 3 A Gly1886Glu NS 0 0 1 Ͻ0.01 40 5687T 3 A Val1896Asp NS 0 0 1 Ͻ0.01 40 5693G 3 A Arg1898His NS 0 0 1 Ͻ0.01 40 5714 ϩ 5g 3 a Splice site NS 0 0 1 Ͻ0.01 42 5843CA 3 TG Pro1948Leu NS 11 7 28 0.04 42 5882G 3 A Gly1961Glu Ͻ0.0001 Yes 1 0 43 0.03 43 5908C 3 T Leu1970Phe NS 1 0 1 Ͻ0.01 43 5917delG FS NS 0 0 1 Ͻ0.01 44 6079C 3 T Leu2027Phe 0.01 Yes 0 0 9 0.01 44 6088C 3 T Arg2030Stop NS 0 0 2 Ͻ0.01 44 6089G 3 A Arg2030Gln NS 0 0 1 Ͻ0.01 44 6112A 3 T Arg2038Trp NS 0 0 1 Ͻ0.01 45 6148A 3 C Val2050Leu NS 1 0 0 Ͻ0.01 46 6212A 3 T Tyr2071Phe NS 0 0 1 Ͻ0.01 45 6229C 3 T Arg2077Trp NS 0 0 2 Ͻ0.01 46 6320G 3 A Arg2107His 0.01 Yes 0 0 10 0.01 46 6383A 3 G His2128Arg NS 0 0 1 Ͻ0.01 47 6446G 3 T Arg2149Leu NS 0 0 1 Ͻ0.01 47 6449G 3 A Cys2150Tyr NS 0 0 5 Ͻ0.01 48 6529G 3 A Asp2177Asn NS 2 0 0 Ͻ0.01 48 6686T 3 C Leu2229Pro NS 0 0 1 Ͻ0.01 48 6707delTCACACAG FS NS 0 0 1 Ͻ0.01 48 6729 ϩ 1g 3 a Splice site NS 0 0 1 Ͻ0.01 49 6764G 3 T Ser2255Ile 0.009 No 16 4 54 0.06 49 6788G 3 T Arg2263Leu NS 0 0 1 Ͻ0.01 (A) The probability under the null hypothesis of similar prevalence of each variant in Stargardt (STGD) compared with non-STGD alleles (two-tailed Fisher`s exact test); (B) compatability of the variant existing in a ratio of 100:1 in STGD to control alleles, calculated using the binomial distribution. 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109 If the three most common missense variants (Asn1868Ile, Ser2255Ile, and Arg943Gln) were not included, missense variants were detected in 34 (9.3%) of 364 AMD alleles and 13 (6.7%) of 192 control alleles. Login to comment
130 However, the nonconservative subset was not more strongly associated with Stargardt disease than the conservative subset, largely because three of the nonconservative changes exhibited a prevalence in non-Stargardt alleles of more than 4% (Asn1868Ile, Arg943Gln, and Ser2255Ile). Login to comment
155 Three missense variants, Gly863Ala, Asn1868Ile, and Ser2255Ile, were significantly enriched among patients with Stargardt disease but not to the extent that would be expected if they were fully penetrant Stargardt alleles. Login to comment
162 The Asn1868Ile variant was found in 71 patients with Stargardt disease and was homozygous in 8 of these. Login to comment
168 The two variants Asn1868Ile and Ser2255Ile occurred together in seven patients with Stargardt disease, one being homozygous for Ser2255Ile and heterozygous for Asn1868Ile. Login to comment
169 They also occurred together in one patient with AMD who was homozygous for Ser2255Ile and heterozygous for Asn1868Ile. Login to comment
171 For instance, Asn1868Ile was always associated with CTC at codon 1894 (Leu3Leu). Login to comment
173 Furthermore, the missense changes Gly863Ala and Arg943Gln were commonly found together. Login to comment
103 Thirty-Three Truncated and 98 Amino Acid-Changing Variants in the ABCA4 Gene Exon Nucleotide Change Effect (A) (B) AMD (n d1d; 182) Control (n d1d; 96) STGD (n d1d; 374) Allele Prevalence 2 106delT FS NS 0 0 1 b0d;0.01 2 160 af9; 1g 3 a Splice site NS 0 0 1 b0d;0.01 3 161G 3 A Cys54Tyr NS 0 0 6 b0d;0.01 3 179C 3 T Ala60Val NS 0 0 2 b0d;0.01 3 194G 3 A Gly65Glu NS 0 0 2 b0d;0.01 3 223T 3 G Cys75Gly NS 0 0 2 b0d;0.01 3 247delCAAA FS NS 0 0 2 b0d;0.01 3 298C 3 T Ser100Pro NS 0 0 1 b0d;0.01 5 454C 3 T Arg152Stop NS 0 0 2 b0d;0.01 6 574G 3 A Ala192Thr NS 0 0 1 b0d;0.01 6 618C 3 G Ser206Arg NS 0 0 3 b0d;0.01 6 634C 3 T Arg212Cys 0.02 Yes 0 0 7 0.01 6 635G 3 A Arg212His NS 2 2 6 0.01 6 658C 3 T Arg220Cys NS 0 0 2 b0d;0.01 6 661delG FS NS 0 0 1 b0d;0.01 666delAAAGACGGTGC 6 GC FS NS 0 0 1 b0d;0.01 6 746A 3 C Asp249Gly NS 0 0 1 b0d;0.01 8 899C 3 A Thr300Asn NS 0 0 1 b0d;0.01 8 997C 3 T Arg333Trp NS 0 0 1 b0d;0.01 9 1140T 3 A Asn380Lys NS 0 0 1 b0d;0.01 9 1222C 3 T Arg408Stop NS 0 0 1 b0d;0.01 10 1268A 3 G His423Arg NS 1 0 7 0.01 10 1335C 3 G Ser445Arg NS 0 0 1 b0d;0.01 10 1344delG FS NS 0 0 1 b0d;0.01 11 1411G 3 A Glu471Lys NS 0 0 3 b0d;0.01 11 1513delATCAC FS NS 0 0 1 b0d;0.01 12 1622T 3 C Leu541Pro 0.001 Yes 0 0 11 0.01 13 1804C 3 T Arg602Trp NS 0 0 3 b0d;0.01 13 1805G 3 A Arg602Gln NS 0 0 1 b0d;0.01 13 1819G 3 T Gly607Trp NS 0 0 1 b0d;0.01 13 1823T 3 A Phe608Ile NS 0 0 1 b0d;0.01 13 1927G 3 A Val643Met NS 0 0 1 b0d;0.01 14 1989G 3 T Trp663Stop NS 0 0 1 b0d;0.01 14 2005delAT FS NS 0 0 3 b0d;0.01 14 2041C 3 T Arg681Stop NS 0 0 2 b0d;0.01 14 2147C 3 T Thr716Met NS 0 0 1 b0d;0.01 15 2291G 3 A Cys764Tyr NS 0 0 1 b0d;0.01 15 2294G 3 A Ser765Asn NS 0 0 1 b0d;0.01 15 2300T 3 A Val767Asp NS 0 0 2 b0d;0.01 16 2385del16bp FS NS 0 0 1 b0d;0.01 16 2453G 3 A Gly818Glu NS 0 0 1 b0d;0.01 16 2461T 3 A Trp821Arg NS 0 0 1 b0d;0.01 16 2546T 3 C Val849Ala NS 0 0 4 b0d;0.01 16 2552G 3 A Gly851Asp NS 0 0 1 b0d;0.01 16 2560G 3 A Ala854Thr NS 0 0 1 b0d;0.01 17 2588G 3 C Gly863Ala 0.0006 No 2 2 28 0.02 17 2617T 3 C Phe873Leu NS 0 0 1 b0d;0.01 18 2690C 3 T Thr897Ile NS 0 0 1 b0d;0.01 18 2701A 3 G Thr901Ala NS 0 1 0 b0d;0.01 18 2703A 3 G Thr901Arg NS 0 0 2 b0d;0.01 19 2828G 3 A Arg943Gln NS 20 13 37 0.05 19 2883delC FS NS 0 0 1 b0d;0.01 20 2894A 3 G Asn965Ser NS 0 0 3 b0d;0.01 19 2912C 3 A Thr971Asn NS 0 0 1 b0d;0.01 19 2915C 3 A Thr972Asn NS 0 0 1 b0d;0.01 20 2920T 3 C Ser974Pro NS 0 0 1 b0d;0.01 20 2966T 3 C Val989Ala NS 0 0 2 b0d;0.01 20 2977del8bp FS NS 0 0 1 b0d;0.01 20 3041T 3 G Leu1014Arg NS 0 0 1 b0d;0.01 21 3055A 3 G Thr1019Ala NS 0 0 1 b0d;0.01 21 3064G 3 A Glu1022Lys NS 0 0 1 b0d;0.01 21 3091A 3 G Lys1031Glu NS 0 0 1 b0d;0.01 21 3113G 3 T Ala1038Val 0.001 Yes 1 0 17 0.01 22 3205insAA FS NS 0 0 1 b0d;0.01 22 3261G 3 A Glu1087Lys NS 0 0 2 b0d;0.01 22 3322C 3 T Arg1108Cys 0.04 Yes 0 0 6 b0d;0.01 22 3323G 3 A Arg1108His NS 0 0 1 b0d;0.01 23 3364G 3 A Glu1122Lys NS 0 0 1 b0d;0.01 (continues) Exon Nucleotide Change Effect (A) (B) AMD (n d1d; 182) Control (n d1d; 96) STGD (n d1d; 374) Allele Prevalence 23 3386G 3 T Arg1129Leu NS 0 0 3 b0d;0.01 24 3531C 3 A Cys1158Stop NS 0 0 1 b0d;0.01 25 3749T 3 C Leu1250Pro NS 0 0 1 b0d;0.01 26 3835delGATTCT FS NS 0 0 1 b0d;0.01 27 3940C 3 A Pro1314Thr NS 0 1 0 b0d;0.01 28 4139C 3 T Pro1380Leu 0.001 Yes 0 0 10 0.01 28 4222T 3 C Trp1408Arg NS 0 0 2 b0d;0.01 28 4223G 3 T Trp1408Leu NS 0 0 2 b0d;0.01 28 4234C 3 T Gln1412stop NS 0 0 1 b0d;0.01 29 4297G 3 A Val1433Ile NS 1 0 0 b0d;0.01 29 4319T 3 C Phe1440Ser NS 0 0 1 b0d;0.01 30 4353 afa; 1g 3 t Splice site NS 0 0 1 b0d;0.01 30 4457C 3 T Pro1486Leu NS 0 0 1 b0d;0.01 30 4462T 3 C Cys1488Arg NS 0 0 3 b0d;0.01 30 4463G 3 T Cys1488Phe NS 0 0 2 b0d;0.01 30 4469G 3 A Cys1490Tyr NS 0 0 3 b0d;0.01 30 4531insC FS NS 0 0 2 b0d;0.01 32 4538A 3 G Gln1513Arg NS 0 0 1 b0d;0.01 30 4539 af9; 1g 3 t Splice site NS 0 0 1 b0d;0.01 31 4574T 3 C Leu1525Pro NS 0 0 1 b0d;0.01 33 4733delGTTT FS NS 0 0 1 b0d;0.01 4859delATAACAinsTCC 35 T FS NS 0 0 1 b0d;0.01 36 4909G 3 A Ala1637Thr NS 0 0 1 b0d;0.01 35 4918C 3 T Arg1640Trp NS 0 0 1 b0d;0.01 35 4919G 3 A Arg1640Gln NS 0 0 1 b0d;0.01 35 4954T 3 G Tyr1652Asp NS 0 0 1 b0d;0.01 36 5077G 3 A Val1693Ile NS 0 0 1 b0d;0.01 36 5186T 3 C Leu1729Pro NS 0 0 2 b0d;0.01 36 5206T 3 C Ser1736Pro NS 0 0 1 b0d;0.01 36 5212del11bp FS NS 0 0 1 b0d;0.01 37 5225delTGGTGGTGGGC FS NS 0 0 1 b0d;0.01 del LPA 37 5278del9bp 1760 NS 0 0 1 b0d;0.01 37 5288delG FS NS 0 0 1 b0d;0.01 38 5395A 3 G Asn1799Asp NS 0 0 1 b0d;0.01 38 5451T 3 G Asp1817Glu NS 1 0 4 b0d;0.01 39 5584 af9; 5g 3 a Splice site 0.02 Yes 0 0 6 b0d;0.01 40 5603A 3 T Asn1868Ile 0.0006 No 20 7 79 0.08 40 5651T 3 A Val1884GLu NS 0 0 1 b0d;0.01 40 5657G 3 A Gly1886Glu NS 0 0 1 b0d;0.01 40 5687T 3 A Val1896Asp NS 0 0 1 b0d;0.01 40 5693G 3 A Arg1898His NS 0 0 1 b0d;0.01 40 5714 af9; 5g 3 a Splice site NS 0 0 1 b0d;0.01 42 5843CA 3 TG Pro1948Leu NS 11 7 28 0.04 42 5882G 3 A Gly1961Glu b0d;0.0001 Yes 1 0 43 0.03 43 5908C 3 T Leu1970Phe NS 1 0 1 b0d;0.01 43 5917delG FS NS 0 0 1 b0d;0.01 44 6079C 3 T Leu2027Phe 0.01 Yes 0 0 9 0.01 44 6088C 3 T Arg2030Stop NS 0 0 2 b0d;0.01 44 6089G 3 A Arg2030Gln NS 0 0 1 b0d;0.01 44 6112A 3 T Arg2038Trp NS 0 0 1 b0d;0.01 45 6148A 3 C Val2050Leu NS 1 0 0 b0d;0.01 46 6212A 3 T Tyr2071Phe NS 0 0 1 b0d;0.01 45 6229C 3 T Arg2077Trp NS 0 0 2 b0d;0.01 46 6320G 3 A Arg2107His 0.01 Yes 0 0 10 0.01 46 6383A 3 G His2128Arg NS 0 0 1 b0d;0.01 47 6446G 3 T Arg2149Leu NS 0 0 1 b0d;0.01 47 6449G 3 A Cys2150Tyr NS 0 0 5 b0d;0.01 48 6529G 3 A Asp2177Asn NS 2 0 0 b0d;0.01 48 6686T 3 C Leu2229Pro NS 0 0 1 b0d;0.01 48 6707delTCACACAG FS NS 0 0 1 b0d;0.01 48 6729 af9; 1g 3 a Splice site NS 0 0 1 b0d;0.01 49 6764G 3 T Ser2255Ile 0.009 No 16 4 54 0.06 49 6788G 3 T Arg2263Leu NS 0 0 1 b0d;0.01 (A) The probability under the null hypothesis of similar prevalence of each variant in Stargardt (STGD) compared with non-STGD alleles (two-tailed Fisher`s exact test); (B) compatability of the variant existing in a ratio of 100:1 in STGD to control alleles, calculated using the binomial distribution. 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110 If the three most common missense variants (Asn1868Ile, Ser2255Ile, and Arg943Gln) were not included, missense variants were detected in 34 (9.3%) of 364 AMD alleles and 13 (6.7%) of 192 control alleles. Login to comment
131 However, the nonconservative subset was not more strongly associated with Stargardt disease than the conservative subset, largely because three of the nonconservative changes exhibited a prevalence in non-Stargardt alleles of more than 4% (Asn1868Ile, Arg943Gln, and Ser2255Ile). Login to comment
156 Three missense variants, Gly863Ala, Asn1868Ile, and Ser2255Ile, were significantly enriched among patients with Stargardt disease but not to the extent that would be expected if they were fully penetrant Stargardt alleles. Login to comment
164 The Asn1868Ile variant was found in 71 patients with Stargardt disease and was homozygous in 8 of these. Login to comment
170 The two variants Asn1868Ile and Ser2255Ile occurred together in seven patients with Stargardt disease, one being homozygous for Ser2255Ile and heterozygous for Asn1868Ile. Login to comment

[hide] Late-onset Stargardt disease is associated with mi... Hum Genet. 2001 Apr;108(4):346-55. Yatsenko AN, Shroyer NF, Lewis RA, Lupski JR
Late-onset Stargardt disease is associated with missense mutations that map outside known functional regions of ABCR (ABCA4).
Hum Genet. 2001 Apr;108(4):346-55., [PMID:11379881]

Abstract [show]
Based on recent studies of the photoreceptor-specific ABC transporter gene ABCR (ABCA4) in Stargardt disease (STGD1) and other retinal dystrophies, we and others have developed a model in which the severity of retinal disease correlates inversely with residual ABCR activity. This model predicts that patients with late-onset STGDI may retain partial ABCR activity attributable to mild missense alleles. To test this hypothesis, we used late-onset STGDI patients (onset: > or =35 years) to provide an in vivo functional analysis of various combinations of mutant alleles. We sequenced directly the entire coding region of ABCR and detected mutations in 33/50 (66%) disease chromosomes, but surprisingly, 11/33 (33%) were truncating alleles. Importantly, all 22 missense mutations were located outside the known functional domains of ABCR (ATP-binding or transmembrane), whereas in our general cohort of STGDI subjects, alterations occurred with equal frequency across the entire protein. We suggest that these missense mutations in regions of unknown function are milder alleles and more susceptible to modifier effects. Thus, we have corroborated a prediction from the model of ABCR pathogenicity that (1) one mutant ABCR allele is always missense in late-onset STGD1 patients, and (2) the age-of-onset is correlated with the amount of ABCR activity of this allele. In addition, we report three new pseudodominant families that now comprise eight of 178 outbred STGD1 families and suggest a carrier frequency of STGD1-associated ABCR mutations of about 4.5% (approximately 1/22).

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106 351 Table 2 Novel and previously reported polymorphic sites identified in the ABCR gene in late-onset STGD subjects and controls (bold novel polymorphic sites) Exon Nucleotide alteration Predicted AA change STGD1 chromosomes Control chromosomes P value Reference 6 635 GÆA R212H 1/50 Simonelli et al. (2000) 7 IVS6-32 TÆC 4/48 N. F. Shroyer et al. (in preparation) 10 IVS9-14CÆÆÆÆT 22/50 (44%) 18/166 (10.8%) P<0.001 Present study 10 1268AÆG H423R 10/50 (20%) 46/170 (27%) P<0.4 Rivera et al. (2000) 10 1269CÆT H423H 4/50 (8%) 7/170 (4%) P<0.2 Rivera et al. (2000) 10 IVS10+11delG 16/50 (32%) 57/170 (33.5%) P>0.5 Papaioannou et al. (2000) 19 2828 GÆA R943Q 4/50 Allikmets et al. (1997b) 28 4203 CÆA P1401P 7/50 Maugeri et al. (1999) 33 IVS33+48TÆÆÆÆC 22/50 (44%) 48/114 (42%) P<0.5 Present study 39 IVS38-10CÆT 1/48 Maugeri et al. (1999) 40 5603AÆT N1868I 8/48 Stone et al. (1998) 41 5814AÆG L1938L 3/50 N. F. Shroyer et al. (in preparation) 42 IVS41-44CÆA 3/48 N. F. Shroyer et al. (in preparation) 42 IVS41-11GÆA 3/48 Maugeri et al. (1999) 42 5844AÆG P1948P 2/48 Maugeri et al. (1999) 44 IVS43-16GÆA 1/48 N. F. Shroyer et al. (in preparation) 44 6069CÆT I2023I 4/50 Allikmets et al. (1997b) 45 6249CÆT I2083I 4/50 Maugeri et al. (1999) 45 IVS45+7GÆA 5/50 (10%) 9/160 (5.6%) P>0.1 Papaioannou et al. (2000) 49 IVS48-3TÆC 3/50 (6%) 10/170 (5.9%) P>0.9 Maugeri et al. (1999) 49 6764GÆT S2255I 3/50 Allikmets et al. (1997b) 49 IVS49+27GÆC 2/48 Papaioannou et al. (2000) All missense mutations in late-onset STGD1 occur outside known functional regions of ABCR The positions of late-onset associated ABCR missense mutations were placed on the predicted ABCR structure that includes four regions of known function (transmembrane and ATP-binding domains in each of two symmetric halves of the protein). Login to comment

[hide] A comprehensive survey of sequence variation in th... Am J Hum Genet. 2000 Oct;67(4):800-13. Epub 2000 Aug 24. Rivera A, White K, Stohr H, Steiner K, Hemmrich N, Grimm T, Jurklies B, Lorenz B, Scholl HP, Apfelstedt-Sylla E, Weber BH
A comprehensive survey of sequence variation in the ABCA4 (ABCR) gene in Stargardt disease and age-related macular degeneration.
Am J Hum Genet. 2000 Oct;67(4):800-13. Epub 2000 Aug 24., [PMID:10958763]

Abstract [show]
Stargardt disease (STGD) is a common autosomal recessive maculopathy of early and young-adult onset and is caused by alterations in the gene encoding the photoreceptor-specific ATP-binding cassette (ABC) transporter (ABCA4). We have studied 144 patients with STGD and 220 unaffected individuals ascertained from the German population, to complete a comprehensive, population-specific survey of the sequence variation in the ABCA4 gene. In addition, we have assessed the proposed role for ABCA4 in age-related macular degeneration (AMD), a common cause of late-onset blindness, by studying 200 affected individuals with late-stage disease. Using a screening strategy based primarily on denaturing gradient gel electrophoresis, we have identified in the three study groups a total of 127 unique alterations, of which 90 have not been previously reported, and have classified 72 as probable pathogenic mutations. Of the 288 STGD chromosomes studied, mutations were identified in 166, resulting in a detection rate of approximately 58%. Eight different alleles account for 61% of the identified disease alleles, and at least one of these, the L541P-A1038V complex allele, appears to be a founder mutation in the German population. When the group with AMD and the control group were analyzed with the same methodology, 18 patients with AMD and 12 controls were found to harbor possible disease-associated alterations. This represents no significant difference between the two groups; however, for detection of modest effects of rare alleles in complex diseases, the analysis of larger cohorts of patients may be required.

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79 Also considered pathological were missense mutations causing nonconservative amino acid changes-for example, A60T and A60E (table 2)-with the exception of those that were found at similar frequencies in the three study groups-for example, R152Q, N1868I, and V1921M (tables 3 and 4). Login to comment
83 Table 4 Polymorphisms in the ABCA4 Gene EXON AND NUCLEOTIDE CHANGE EFFECT NO. OF ALLELES REFERENCE(S) STGD (n p 288) AMD (n p 400) Control (n p 440) 6: 635GrA R212H 8 8 32 This study 7: IVS6-32TrC Unknown 53 115 130 This study 10: 1267ArG H423R 52 79 101 This study 1268CrT H423H 11 17 17 This study 14: IVS14ϩ50TrCa Unknown 22 18 9 This study 19: 2828GrAa R943Q 23 14 10 Allikmets et al. (1997a, 1997b), Maugeri et al. (1999), Papaioannou et al. (2000) 28: 4203CrA P1401P 29 13 20 Maugeri et al. (1999) 33: IVS32-38CrT Unknown 1 4 12 This study 34: IVS33-16delGT Unknown 24 8 12 This study 40: 5603ArT N1868I 37 40 46 Maugeri et al. (1999) 5682GrC L1894L 73 52 91 Maugeri et al. (1999), Papaioannou et al. (2000) 41: 5814ArG L1938L 50 68 70 This study 42: IVS41-11GrA Unknown 46 56 55 Maugeri et al. (1999) 5844ArG P1948P 40 40 39 Maugeri et al. (1999), Papaioannou et al. (2000) 5843CArTG P1948L 5 14 13 Maugeri et al. (1999) 44: IVS43-16GrA Unknown 46 48 55 Papaioannou et al. (2000) 45: IVS45ϩ7GrA Unknown 10 15 11 Papaioannou et al. (2000) 6249CrT I2083I 13 17 27 Allikmets et al. (1997a), Maugeri et al. (1999) 46: 6285TrC D2095D 38 36 33 Maugeri et al. (1999) a 2828GrA and IVS14ϩ50TrC occur on the same haplotype together with 2588GrC. Login to comment
101 Nineteen different alterations were present in 11% of the control alleles and were classified as polymorphisms (table 4); these include five nonconservative amino acid substitutions (R212H, H423R, R943Q, N1868I, and P1948L). Login to comment

[hide] Analysis of the Stargardt disease gene (ABCR) in a... Ophthalmology. 1999 Aug;106(8):1531-6. De La Paz MA, Guy VK, Abou-Donia S, Heinis R, Bracken B, Vance JM, Gilbert JR, Gass JD, Haines JL, Pericak-Vance MA
Analysis of the Stargardt disease gene (ABCR) in age-related macular degeneration.
Ophthalmology. 1999 Aug;106(8):1531-6., [PMID:10442900]

Abstract [show]
PURPOSE: Age-related macular degeneration (AMD) is a complex genetic disorder and the leading cause of severe vision loss in the elderly. The Stargardt disease gene (ABCR) has been proposed as a major genetic risk factor in AMD. The purpose of this study was to evaluate the authors' AMD population for the specific ABCR variants proposed previously as genetic risk factors for AMD. METHODS: The authors screened their AMD population (159 familial cases from 112 multiplex families and 53 sporadic cases) and 56 racially matched individuals with no known history of AMD from the same clinic population for evidence of the ABCR variants. Grading of disease severity was performed according to a standard protocol. Patients with extensive intermediate drusen or large soft drusen, drusenoid retinal pigment epithelial (RPE) detachments, geographic atrophy of the RPE, or evidence of exudative maculopathy were considered affected. Analysis for variants was performed by polymerase chain reaction amplification of individual exons of the ABCR gene with flanking primers and a combination of single-strand conformation polymorphism, heteroduplex analysis, and high-performance liquid chromatography. All abnormal conformers detected using these techniques were characterized by direct sequencing. RESULTS: The authors identified only two of the previously reported variants in their study population. Both variants occurred in sporadic cases, and none was found in familial cases or the randomly selected population. In addition, the authors identified several newly described polymorphisms and variants in both the AMD and control populations. CONCLUSIONS: Based on these initial findings, the authors suggest that ABCR is not a major genetic risk factor for AMD in their study population. Additional genetic studies are needed to more fully evaluate the role of ABCR in AMD.

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95 One polymorphism (N1868I) occurred in both the randomly selected population group and affected subjects and failed to segregate with the disease phenotype in the families. Login to comment
131 of Controls (%) P862L 2682 C 3 T 2683 C 3 T 3/112 (3.6) 3/53 (3.8) 0/56 (0) T901A 2782 A 3 G 2/112 (1.8) 0/53 (0) 1/56 (1.8) N1868I 5684 A 3 T 3/112 (2.7) 4/53 (7.5) 4/56 (7.1) L1948P* 5924 T 3 C 112/112 (100) 53/53 (100) 56/56 (100) L1948P* 5924 T 3 C 5925 G 3 A 110/112 (98) 51/53 (96) 54/56 (96) I2023I 6150 C 3 T 9/112 (8) 5/53 (9.4) 3/56 (5.4) L2026L 6160 C 3 T 0/112 (0) 0/53 (0) 0/56 (0) I2083I 6330 C 3 T 9/112 (8) 4/53 (7.5) 5/56 (8.9) * Variants identified in probands only. Login to comment

[hide] Allelic variation in ABCR associated with Stargard... Nat Genet. 1998 Dec;20(4):328-9. Stone EM, Webster AR, Vandenburgh K, Streb LM, Hockey RR, Lotery AJ, Sheffield VC
Allelic variation in ABCR associated with Stargardt disease but not age-related macular degeneration.
Nat Genet. 1998 Dec;20(4):328-9., [PMID:9843201]

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23 The 3 common variants (Asn1868Ile, Arg943Gln and Ser2255Ile) were all present in more than 4% of all 3 groups. Login to comment
69 Three non-conservative variants (Asn1868Ile, Arg943Gln and Ser2255Ile) were very common (>4%) in all three groups. Login to comment
78 Neither of these changes was detected by Dean et al. nor did they detect a very common (15.8% overall in our study) non-conservative sequence change in exon 40 (Asn1868Ile). Login to comment

[hide] ABCA4 mutational spectrum in Mexican patients with... Exp Eye Res. 2013 Apr;109:77-82. doi: 10.1016/j.exer.2013.02.006. Epub 2013 Feb 16. Chacon-Camacho OF, Granillo-Alvarez M, Ayala-Ramirez R, Zenteno JC
ABCA4 mutational spectrum in Mexican patients with Stargardt disease: Identification of 12 novel mutations and evidence of a founder effect for the common p.A1773V mutation.
Exp Eye Res. 2013 Apr;109:77-82. doi: 10.1016/j.exer.2013.02.006. Epub 2013 Feb 16., [PMID:23419329]

Abstract [show]
The aim of this study was to assess the mutational spectrum of the ABCA4 gene in a cohort of patients with Stargardt disease from Mexico, a previously uncharacterized population. Clinical diagnosis in each patient was supported by a complete ophthalmological assessment that included visual acuity measurement, a slit lamp examination, a fundus examination and photography, electroretinography, fluorescein angiography, and computerized visual fields testing. Molecular analysis was performed by PCR amplification and direct nucleotide sequence of the 50 exons of the ABCA4 gene in genomic DNA. A total of 31 unrelated subjects with the disease were enrolled in the study. Molecular analysis in the total group of 62 alleles allowed the identification of 46 mutant ABCA4 alleles carrying 29 different pathogenic disease-associated mutations. Two ABCA4 mutant alleles were detected in 20 of the 31 patients (64.5%), a single disease allele was identified in six (19.4%), and no mutant alleles were detected in five of the cases (16.1%). Most patients with two ABCA4 mutations (11/20, 55%) were compound heterozygotes. Twelve variants were novel ABCA4 mutations. Nucleotide substitutions were the most frequent type of variation, occurring in 26 out of 29 (89.7%) different mutations. The two most common mutations in our study were the missense changes p.A1773V and p.G818E, which were identified in eight (17%) and seven (15%) of the total 46 disease-associated alleles, respectively. Haplotype analyses of intragenic SNPs in four subjects carrying the p.A1773V mutation supported a common origin for this mutation. In conclusion, this is the first report of ABCA4 molecular screening in Latin American Stargardt disease patients. Our results expand the mutational spectrum of the disease by adding 12 novel ABCA4 pathogenic variants and support the occurrence of a founder effect for the p.A1773V mutation in the Mexican population. The identification of recurrent mutations in our cohort will direct future ABCA4 molecular screening in patients from this ethnic group.

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82 These mutations were p.R24W, p.G818E, p.P1380L, p.V1682_V1686del, p.R1705Q, p.A1773V, p.I1775N, p.Y1779H, and p.N1868I. Login to comment
100 Allele 1 Allele 2 Genotype Exon Nucleotide change Polypeptide change Exon Nucleotide change Polypeptide change Familial case # 1 38 c.5318C>T p.A1773V (D) 38 c.5318C>T p.A1773V (D) Homozygous 2 e NI e e NI e e 3 6 c.634C>T p.R212C (D) 38 c.5318C>T p.A1773V (D) Compound heterozygous 4 23 c.3386G>T p.R1129L (D) 28 c.4139C>T p.P1380L (D) Compound heterozygous 5 e NI e e NI e e 6 38 c.5318C>T p.A1773V (D) 38 c.5318C>T p.A1773V (D) Homozygous 7 e NI e e NI e e 8 16 c.2453G>A p.G818E (D) 28 c.4249_4251 delTTC p.F1417del (D; N) Compound heterozygous 9 38 c.5318C>T p.A1773V (D) 38 c.5318C>T p.A1773V (D) Homozygous Sporadic case # 1 8 c.868C>T p.R290W (D) e IVS8&#fe;1G>A Splicing (D; N) Compound heterozygous 2 38 c.5318C>T p.A1773V (D) - NI - Heterozygous 3 20 c.3041T>G p.L1014R (D) 1; 49 c.52C>T; c.6764G>T p.R18W (D); p.S2255I (B) Compound heterozygous 4 13; 19 c.1804C>T; c.2828G>A p.R602W (D); p.R943Q (U) 16 c.2453G>A p.G818E (D) Compound heterozygous 5 38 c.5324T>A p. I1775N (D; N) 38 c.5324T>A p.I1775N (D; N) Homozygous 6 e NI e e NI e e 7 49 c.6764G>T p.S2255I (B) 49 c.6764 G>T p.S2255I (B) Homozygous 8 19; 40 c.2828 G>A; c.5503A>T p.R943Q (U); p.N1868I (U) 3 c.265G>T p.E89* (D; N) Compound heterozygous 9 38 c.5335T>C p.Y1779H (D;N) 38 c.5335T>C p.Y1779H (D;N) Homozygous 10 16 c.2453G>A p.G818E (D) 16 c.2453G>A p.G818E (D) Homozygous 11 6 c.723A>T p.E241D (D;N) 36 c.5114G>A p.R1705Q (D) Compound heterozygous 12 2 c.71G>A (D) p.R24H e NI e Heterozygous 13 30 c.4537_4538insC p.Q1513Pfs*41 (D; N) e NI e Heterozygous 14 32 c.4667G>C p.R1556T (D; N) 32 c.4667G>C p.R1556T (D; N) Homozygous 15 45 c.6221G>T p.G2074V (D; N) 16 c.2453G>A p.G818E (D) Compound heterozygous 16 16; 41 c.2453G>A; c.5824G>C p. G818E (D); p. E1942Q (B;N) 46 c.6384A>G p.H2128R (D) Compound heterozygous 17 16 c.2453G>A p. G818E (D) e NI e Heterozygous 18 32 c.4653G>A p. W1551* (D; N) e NI e Heterozygous 19 23 c.3386G>T p. R1129L (D) e NI e Heterozygous 20 36 c.5045_5059del GTTGCCATCTGCGTG p.V1682_ V1686del (D; N) 29; 49 c.4328G>A; c.6764G>T p.R1443H (D); p.S2255I (B) Compound heterozygous 21 19 c.2894A>G p.N965S (D) 19 c.2894A>G p.N965S (D) Homozygous 22 e NI e e NI e e STGD accounts for approximately 7% of all retinal dystrophies; it is one of the most common genetic forms of juvenile or early adult onset macular degeneration. Login to comment
119 ABCA4 Exon # Nucleotide change Predicted protein effect Number of alleles Population genotypic frequency in EVS Population allelic frequency in EVS (%) 1 c.52C>T p.R18W 1 TT &#bc; 0/TC &#bc; 2/CC &#bc; 6501 T &#bc; 0.015/C &#bc; 99.985 2 c.71G>A p.R24H 1 AA &#bc; 0/AG &#bc; 1/GG &#bc; 6502 A &#bc; 0.008/G &#bc; 99.992 3 c.265G>T p.E89* (N) 1 NR NR 6 c.634C>T p.R212C 1 TT &#bc; 0/TC &#bc; 2/CC &#bc; 6501 T &#bc; 0.015/C &#bc; 99.985 6 c.723A>T p.E241D (N) 1 NR NR 8 c.868C>T p.R290W 1 NR NR IVS8 IVS8 &#fe; 1G>A Splicing mutation (N) 1 NR NR 13 c.1804C>T p.R602W 1 NR NR 16 c.2453G>A p.G818E 7 NR NR 19 c.2828G>A p.R943Q 2 AA &#bc; 8/AG &#bc; 400/GG &#bc; 6095 A &#bc; 3.199/G &#bc; 96.801 19 c.2894A>G p.N965S 2 GG &#bc; 0/GA &#bc; 1/AA &#bc; 6502 G &#bc; 0.008/A &#bc; 99.992 20 c.3041T>G p.L1014R 1 NR NR 23 c.3386G>T p.R1129L 2 NR NR 28 c.4139C>T p.P1380L 1 TT &#bc; 0/TC &#bc; 2/CC &#bc; 6501 T &#bc; 0.015/C &#bc; 99.985 28 c.4249_4251del TTC p.F1417del (N) 1 NR NR 29 c.4328G>A p.R1443H 1 AA &#bc; 0/AG &#bc; 1/GG &#bc; 6502 A &#bc; 0.008/G &#bc; 99.992 30 c.4537_4538insC p.Q1513Pfs*41 (N) 1 NR NR 32 c.4653G>A p.W1551* (N) 1 NR NR 32 c.4667G>C p.R1556T (N) 2 NR NR 36 c.5044_5058del GTTGCCATCTGCGTG p.V1682_V1686del (N) 1 NR NR 36 c.5114G>A p.R1705Q 1 AA &#bc; 0/AG &#bc; 1/GG &#bc; 6502 A &#bc; 0.008/G &#bc; 99.992 38 c.5318C>T p.A1773V 8 NR NR 38 c.5324T>A p.I1775N (N) 2 NR NR 38 c.5335T>C p.Y1779H (N) 2 NR NR 40 c.5503A>T p.N1868I 1 TT &#bc; 16/TA &#bc; 589/AA &#bc; 5898 T &#bc; 4.775/A &#bc; 95.225 41 c.5824G>C p.E1942Q (N) 1 NR NR 45 c.6221G>T p.G2074V (N) 1 NR NR 46 c.6384A>G p.H2128R 1 NR NR 49 c.6764G>T p.S2255I 4 TT &#bc; 516/TG &#bc; 1473/GG &#bc; 4514 T &#bc; 19.26/G &#bc; 80.74 gold standard for ABCA4 mutational screening. Login to comment
126 Interestingly, five out of 46 mutant alleles (11%) were complex alleles (p.R18W &#fe; p.S2255I; p.R602W &#fe; p.R943W; p.R943W &#fe; p.N1868I; p.G818E &#fe; p.E1942Q; and p.R1443H &#fe; p.S2255I), a frequency that is in agreement with previous reports (Lewis et al., 1999; Shroyer et al., 2001; Zernant et al., 2011). Login to comment
138 It is important to make note that three of the variants identified in this work, p.R943Q, p.N1868I, and p.S2255I have an allele frequency in the NHLBI Exome Sequencing Project of 3.2%, 4.8%, and 19% respectively, and thus they are most probably non-pathogenic variants. Login to comment
139 However, with the exception of sporadic case #7 who was homozygous for p.S2255I (sporadic case #7 in Table 1), all remaining 4 patients carrying one of such mutations also carry two additional deleterious ABCA4 mutations (sporadic cases #4, #3, and #20 in Table 1) or a null allele (p.E89*) combined with p.R943Q and p.N1868I (sporadic case #8). Login to comment
141 Moreover, in vitro studies have shown that the ATPase activity of the p.R943Q protein function was reduced about 40% with respect to wild type ABCA4 (Su&#e1;rez et al., 2002) and carriers of p.N1868I variant exhibit a more than twofold risk of developing STGD than those carrying the normal homozygous variant (Aguirre-Lamban et al., 2011). Login to comment
142 Thus, despite its prevalence in general population, the role of the p.R943Q and N1868I ABCA4 mutations in STGD disease is controversial. Login to comment

[hide] Novel mutations in CRB1 and ABCA4 genes cause Lebe... Eur J Hum Genet. 2013 Nov;21(11):1266-71. doi: 10.1038/ejhg.2013.23. Epub 2013 Feb 27. Jonsson F, Burstedt MS, Sandgren O, Norberg A, Golovleva I
Novel mutations in CRB1 and ABCA4 genes cause Leber congenital amaurosis and Stargardt disease in a Swedish family.
Eur J Hum Genet. 2013 Nov;21(11):1266-71. doi: 10.1038/ejhg.2013.23. Epub 2013 Feb 27., [PMID:23443024]

Abstract [show]
This study aimed to identify genetic mechanisms underlying severe retinal degeneration in one large family from northern Sweden, members of which presented with early-onset autosomal recessive retinitis pigmentosa and juvenile macular dystrophy. The clinical records of affected family members were analysed retrospectively and ophthalmological and electrophysiological examinations were performed in selected cases. Mutation screening was initially performed with microarrays, interrogating known mutations in the genes associated with recessive retinitis pigmentosa, Leber congenital amaurosis and Stargardt disease. Searching for homozygous regions with putative causative disease genes was done by high-density SNP-array genotyping, followed by segregation analysis of the family members. Two distinct phenotypes of retinal dystrophy, Leber congenital amaurosis and Stargardt disease were present in the family. In the family, four patients with Leber congenital amaurosis were homozygous for a novel c.2557C>T (p.Q853X) mutation in the CRB1 gene, while of two cases with Stargardt disease, one was homozygous for c.5461-10T>C in the ABCA4 gene and another was carrier of the same mutation and a novel ABCA4 mutation c.4773+3A>G. Sequence analysis of the entire ABCA4 gene in patients with Stargardt disease revealed complex alleles with additional sequence variants, which were evaluated by bioinformatics tools. In conclusion, presence of different genetic mechanisms resulting in variable phenotype within the family is not rare and can challenge molecular geneticists, ophthalmologists and genetic counsellors.

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89 Of the exonic variants, only p.N1868I and p.H423R were non-synonymous. Login to comment
90 Bioinformatics analysis predicted p.N1868I to be possibly damaging for protein function, whereas p.H423R was predicted to be benign. Login to comment
91 Segregation analysis was done for three ABCA4 sequence variants, including p.N1868I, c.4773&#fe; 3A4G and c.5461-10T4C. Login to comment
92 The variant p.N1868I was found in homozygous form in STGD1 patient VI:10, and in heterozygous form in STGD1 patient V:4 and non-affected individuals V:6, V:7 and VI:8 (Figure 1a). Login to comment
93 To determine if p.N1868I was a common variant in our population, we tested 115 control individuals from a matched geographic region and detected 16 heterozygous carriers. Login to comment
117 None of our healthy controls carried the c.5461-10T4C mutation, in line with previous observations of different population carrier frequencies.35 Interestingly, our STGD1 patients carried the sequence variant ABCA4 p.N1868I that was predicted to be possibly damaging, as well as acting as a risk-increasing factor in AMD.36 In our study, this variant was detected in almost 14% of the healthy controls, which is higher compared with the maximal frequency of 7.5% reported in a Finnish population in the 1000 Genomes project.36 It is worth mentioning that ABCA4 c.2588G4C (p.G863A), the most frequent autosomal recessive mutation in the European population, is disease causative only in combination with a severe ABCA4 mutation,32 and does not result in a STGD1 phenotype when present bi-allelic or in combination with a mild ABCA4 mutation. Login to comment
119 The same phenomena can also be applied to p.N1868I. Login to comment
124 This result was not unexpected, as ABCA4 mRNA is expressed exclusively in retina.38 Table 3 ABCA4 sequence variants in STGD1 patient Position Nucleotide change Amino-acid change RefSNP SIFT PolyPhen Splice site effect MAF (minor allele frequency) Exon 10 c.1268A4G p.H423R rs3112831 Tolerated Benign - C &#bc; 0.246/538b Exon 28 c.4203C4A p.P1401P rs1801666 -a - - A &#bc; 0.005/12b Exon 40 c.5603A4T p.N1868I rs1801466 Possibly damaging Possibly damaging - A &#bc; 0.029/63b A &#bc; 0.139/115c Exon 40 c.5682G4C p.L1894L rs1801574 - - - G &#bc; 0.219/478b - Intron 3 c.302 &#fe; 26A4G - rs2297634 - - None T &#bc; 0.470/1026b Intron 7 c.769-32T4C - rs526016 - - None G &#bc; 0.228/497b Intron 9 c.1240-14C4T - rs4147830 - - None G &#bc; 0.477/1041b Intron 13 c.1761-54G4A - rs4147833 - - Cryptic site T &#bc; 0.377/824b Intron 26 c.3863-73_3863-64delA - rs4147892 - - None NAb Intron 33 c.4773 &#fe; 3A4G New variant - - Weak NAb G &#bc; 0.009/113c Intron 38 c.5461-10T4C rs1800728 - - Weak NAb C &#bc; 0.000/116c Intron 38 c.5461-51delA rs4147899 - - none &#bc; 0.215/469b aNot predictable. Login to comment

[hide] Common synonymous variants in ABCA4 are protective... BMC Ophthalmol. 2015 Mar 6;15:18. doi: 10.1186/s12886-015-0008-0. Grassmann F, Bergholz R, Mandl J, Jagle H, Ruether K, Weber BH
Common synonymous variants in ABCA4 are protective for chloroquine induced maculopathy (toxic maculopathy).
BMC Ophthalmol. 2015 Mar 6;15:18. doi: 10.1186/s12886-015-0008-0., [PMID:25884411]

Abstract [show]
BACKGROUND: Chloroquine (CQ) and hydroxychloroquine (HCQ) are used to treat auto-immune related diseases such as rheumatoid arthritis (RA) or systemic lupus erythematosus. Both drugs however can cause retinal toxicity eventually leading to irreversible maculopathy and retinopathy. Established risk factors are duration and dosage of treatment while the involvement of genetic factors contributing to toxic maculopathy is largely unclear. To address the latter issue, this study aimed to expand on earlier efforts by (1) evaluating risk-altering variants known to be associated with age-related macular degeneration (AMD), a frequent maculopathy in individuals over 55 years of age, and (2) determining the contribution of genetic variants in the coding sequence of the ABCA4 gene. METHODS: The ABCA4 gene was analyzed by deep sequencing technology using a personal genome machine (Ion Torrent) with 200 bp read length. Assessment of AMD variants was done by restriction enzyme digestion of PCR products and TaqMan SNP genotyping. Effect sizes, p-values and confidence intervals of common variants were evaluated by logistic regression (Firth's bias corrected). To account for multiple testing, p-values were adjusted according to the false discovery rate. RESULTS: We found no effects of known AMD-associated variants on the risk of toxic maculopathy. In contrast, we report a statistically significant association of common variants in the ABCA4 gene with retinal disease, assessed by a score-based variance-component test (PSKAT = 0.0055). This association remained significant after adjustment for environmental factors like age and duration of medication and was driven by three common variants in ABCA4 (c.5682G > C, c.5814A > G, c.5844A > G), all conferring a reduced risk for toxic maculopathy. CONCLUSIONS: Our findings demonstrate that minor alleles of common genetic variants in ABCA4 significantly reduce susceptibility to develop toxic maculopathy under CQ treatment. A refined risk profile based on genetic and environmental factors may have implications for revised recommendations in CQ as well as HCQ treatment.

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95 Table 2 Genetic variants identified in ABCA4 sequence analysis in CQ-treated patients with (cases) and without (controls) toxic maculopathy Frequency in Variant (NM_000350.2) Amino acid exchange (NP_000341.2) Cases Controls EURߤ Raw p-value FDR# c.324G > A M114I 0.00 0.04 - - - c.635G > A R212H 0.06 0.08 0.06 - - c.1268A > G* H423R 0.29 0.23 0.30 0.58783 0.58783 c.1269C > T H423H 0.13 0.04 0.07 - - c.1622T > C L541P 0.02 0.00 - - - c.2588G > C G863A 0.00 0.04 0.00 - - c.2828G > A R943Q 0.04 0.12 0.04 - - c.3113C > T A1038V 0.02 0.00 0.00 - - c.4203C > A P1401P 0.00 0.04 - - - c.4297G > A V1433I 0.00 0.04 0.00 - - c.5603A > T N1868I 0.06 0.08 0.07 - - c.5682G > C* L1894L 0.13 0.38 0.26 0.02292 0.030 c.5814A > G* L1938L 0.06 0.31 0.18 0.00722 0.014 c.5843C > T P1948L 0.04 0.08 0.04 - - c.5844A > G* P1948P 0.06 0.31 0.19 0.00722 0.014 c.6069T > C I2023I 0.04 0.08 0.06 - c.6148G > C V2050L 0.02 0.00 0.00 - - c.6249C > T I2083I 0.04 0.08 0.05 - - c.6282 + 7G > A - 0.04 0.08 0.05 - - c.6285T > C D2095D 0.08 0.15 0.10 - - c.6357A > G E2119E 0.02 0.00 - - - c.6730-3T > C - 0.02 0.12 0.02 - - c.6764G > T S2255I 0.02 0.12 0.02 - - *Common variants (combined frequency in cases and controls > 11.6%). Login to comment