ABCMdb

PMID: 11346402

Guymer RH, Heon E, Lotery AJ, Munier FL, Schorderet DF, Baird PN, McNeil RJ, Haines H, Sheffield VC, Stone EM
Variation of codons 1961 and 2177 of the Stargardt disease gene is not associated with age-related macular degeneration.
Arch Ophthalmol. 2001 May;119(5):745-51., [PubMed]

Sentences

No. Mutations Sentence Comment

1 ABCA4 p.Gly1961Glu ABCA4 p.Gly1961Glu ABCA4 p.Asp2177Asn Secondary objectives were to investigate differences in frequency of the G1961E allele in selected ethnic groups as well as to examine the segregation of both G1961E and D2177N alleles in 5 multiplex families with AMD. Login to comment 6 ABCA4 p.Gly1961Glu The number of subjects exhibiting the G1961E orD2177NvariantswerecomparedbetweenAMDandcon- trol groups using a 2-tailed Fisher exact test. Login to comment 7 ABCA4 p.Gly1961Glu ABCA4 p.Gly1961Glu ABCA4 p.Asp2177Asn ABCA4 p.Asp2177Asn Results: There was no significant difference (PϾ.1) in the frequency of the G1961E and D2177N alleles in patients with AMD (2.2%) vs controls (1.0%). Login to comment 8 ABCA4 p.Gly1961Glu ABCA4 p.Gly1961Glu In contrast, there was a significant difference (PϽ.001) in the frequency of the G1961E alleles between normal individuals of Somali ancestry (11.3%) and normal individuals from other populations (0.4%). Login to comment 11 ABCA4 p.Gly1961Glu Conclusions: Somali ancestry is more than 100 times more strongly associated with presence of the G1961E allele than the AMD phenotype. Login to comment 12 ABCA4 p.Gly1961Glu ABCA4 p.Asp2177Asn This study did not find any statistically significant evidence for involvement of the G1961E or D2177N alleles of the ABCA4 gene in AMD. Login to comment 24 ABCA4 p.Gly1961Glu ABCA4 p.Gly1961Glu ABCA4 p.Asp2177Asn (1) The primary purpose was to try to clarify the role of ABCA4 in AMD by screening a large cohort of patients with AMD and ethnically matched controls for the presence of the 2 sequence variations (G1961E and D2177N) that were most highly associated with AMD in the study by Allikmets et al.7 (2) A secondary purpose was to investigate the variation in allele frequency of G1961E among selected ethnic groups. Login to comment 25 ABCA4 p.Gly1961Glu ABCA4 p.Gly1961Glu ABCA4 p.Gly1961Glu ABCA4 p.Asp2177Asn ABCA4 p.Asp2177Asn (3) The final purpose was to examine the segregation of the G1961E and D2177N alleles in 5 multiplex families with AMD from Australia. Login to comment 26 ABCA4 p.Gly1961Glu ABCA4 p.Gly1961Glu ABCA4 p.Asp2177Asn ABCA4 p.Asp2177Asn RESULTS The distributions of G1961E and D2177N sequence variations in the various AMD and control populations are summarized in Table 1. Login to comment 27 ABCA4 p.Gly1961Glu ABCA4 p.Asp2177Asn RESULTS The distributions of G1961E and D2177N sequence variations in the various AMD and control populations are summarized in Table 1. Login to comment 28 ABCA4 p.Gly1961Glu ABCA4 p.Gly1961Glu ABCA4 p.Asp2177Asn ABCA4 p.Asp2177Asn Five instances of the G1961E variation and 7 instances of the D2177N change were observed among the patients with AMD, while 3 instances of G1961E and 4 of D2177N were observed among the controls. Login to comment 29 ABCA4 p.Gly1961Glu ABCA4 p.Gly1961Glu ABCA4 p.Asp2177Asn ABCA4 p.Asp2177Asn Five instances of the G1961E variation and 7 instances of the D2177N change were observed among the patients with AMD, while 3 instances of G1961E and 4 of D2177N were observed among the controls. Login to comment 30 ABCA4 p.Gly1961Glu ABCA4 p.Asp2177Asn A Fisher exact test revealed the differences in allele frequency between these groups to be insignificant whether the alleles were considered together or separately (PϾ.10 in all cases) even without correction for multiple measurements.27 Collectively, the G1961E and D2177N sequence changes were found in 2.2% of the 544 patients with AMD in this study, ranging from 0.99% in patients from the United States to 5.1% in patients from Switzerland. Login to comment 31 ABCA4 p.Gly1961Glu ABCA4 p.Asp2177Asn A Fisher exact test revealed the differences in allele frequency between these groups to be insignificant whether the alleles were considered together or separately (P..10 in all cases) even without correction for multiple measurements.27 Collectively, the G1961E and D2177N sequence changes were found in 2.2% of the 544 patients with AMD in this study, ranging from 0.99% in patients from the United States to 5.1% in patients from Switzerland. Login to comment 42 ABCA4 p.Gly1961Glu MOLECULAR ANALYSIS The DNA was extracted from venous blood as previously described.24 Exons 42 and 48 (containing codons 1961 and 2177 respectively) of the ABCA4 gene were amplified using previously reported oligonucleotide primers.7,25 The G1961E variant was detected using a Taq 1 restriction digestion as follows. Login to comment 43 ABCA4 p.Gly1961Glu MOLECULAR ANALYSIS The DNA was extracted from venous blood as previously described.24 Exons 42 and 48 (containing codons 1961 and 2177 respectively) of the ABCA4 gene were amplified using previously reported oligonucleotide primers.7,25 The G1961E variant was detected using a Taq 1 restriction digestion as follows. Login to comment 44 ABCA4 p.Gly1961Glu Five microliters of the digested product were electrophoresed on 6% polyacrylamide, 5% glycerol nondenaturing gels, and stained with silver nitrate using a standard protocol.26 The G1961E allele was recognized by the appearance of 2 new fragments 135 base pair (bp) and 77 bp in size and confirmed by automated DNA sequencing using dye-terminator chemistry and an ABI 377 sequencer. Login to comment 45 ABCA4 p.Gly1961Glu ABCA4 p.Asp2177Asn The D2177N allele was detected by single-strand conformation polymorphism analysis. Login to comment 46 ABCA4 p.Asp2177Asn The D2177N allele was detected by single-strand conformation polymorphism analysis. Login to comment 49 ABCA4 p.Gly1961Glu ABCA4 p.Asp2177Asn STATISTICAL ANALYSIS The proportion of subjects showing the G1961E or D2177N variant were compared between AMD and control groups using the Fisher exact test (2-tailed). Login to comment 50 ABCA4 p.Gly1961Glu ABCA4 p.Asp2177Asn STATISTICAL ANALYSIS The proportion of subjects showing the G1961E or D2177N variant were compared between AMD and control groups using the Fisher exact test (2-tailed). Login to comment 54 ABCA4 p.Gly1961Glu Two of these 5 individuals were homozygous for G1961E, and both of them were patients with Somali ancestry. Login to comment 55 ABCA4 p.Gly1961Glu ABCA4 p.Gly1961Glu The fact that these were the only 2 Stargardt probands in the entire cohort who were known to have Somali ancestry suggested that the G1961E allele frequency might be much higher in individuals from Somalia than those from other ethnic backgrounds. Login to comment 56 ABCA4 p.Gly1961Glu ABCA4 p.Gly1961Glu To test this hypothesis, 62 unrelated normal individuals with Somali ancestry were screened for the G1961E change, and 7 were found to be heterozygous for this variant (11.2%). Login to comment 57 ABCA4 p.Gly1961Glu ABCA4 p.Gly1961Glu Table 2 gives the result of sequential comparisons (Fisher exact test) of the frequency of the G1961E change in normal individuals in Somalia and normal individuals from our other study populations. Login to comment 58 ABCA4 p.Gly1961Glu ABCA4 p.Gly1961Glu The frequency of the G1961E change is significantly greater in normal individuals of Somali ancestry than in normal individuals from other ethnic backgrounds. Login to comment 59 ABCA4 p.Gly1961Glu ABCA4 p.Gly1961Glu Table 3 gives a similar set of sequential comparisons between the frequency of the G1961E change in normal individuals from Somalia and the frequency of the change in patients with AMD in our study. Login to comment 60 ABCA4 p.Gly1961Glu ABCA4 p.Gly1961Glu The frequency of the G1961E change is significantly greater in unaffected individuals from Somalia than in the entire cohort of patients with AMD in this study (PϽ.001). Login to comment 61 ABCA4 p.Gly1961Glu ABCA4 p.Gly1961Glu ABCA4 p.Asp2177Asn Five of the 7 AMD probands from Australia who harbored a G1961E or D2177N change had family members who also carried the clinical diagnosis of AMD. Login to comment 62 ABCA4 p.Gly1961Glu ABCA4 p.Asp2177Asn Five of the 7 AMD probands from Australia who harbored a G1961E or D2177N change had family members who also carried the clinical diagnosis of AMD. Login to comment 64 ABCA4 p.Gly1961Glu ABCA4 p.Asp2177Asn Of the 15 family members diagnosed with AMD, 8 harbored a G1961E or D2177N change. Login to comment 65 ABCA4 p.Gly1961Glu ABCA4 p.Asp2177Asn Of the 15 family members diagnosed with AMD, 8 harbored a G1961E or D2177N change. Login to comment 68 ABCA4 p.Gly1961Glu ABCA4 p.Asp2177Asn The G1961E or D2177N sequence variations were found in 6 of the patients (2.7%) with CNV and 6 of the patients (2.5%) who were free from this complication. Login to comment 69 ABCA4 p.Gly1961Glu ABCA4 p.Asp2177Asn The G1961E or D2177N sequence variations were found in 6 of the patients (2.7%) with CNV and 6 of the patients (2.5%) who were free from this complication. Login to comment 70 ABCA4 p.Gly1961Glu G1961E Association With Age-Related Macular Degeneration* Location No. Login to comment 71 ABCA4 p.Gly1961Glu G1961E Association With Age-Related Macular Degeneration* Location No. Login to comment 117 ABCA4 p.Gly1961Glu G1961E Association With Ethnicity (Somali Controls vs Other Controls)* Location No. Login to comment 118 ABCA4 p.Gly1961Glu G1961E Association With Ethnicity (Somali Controls vs Other Controls)* Location No. Login to comment 122 ABCA4 p.Gly1961Glu G1961E Association With Ethnicity (Somali Controls vs Patients With AMD)* Location No. Login to comment 123 ABCA4 p.Gly1961Glu G1961E Association With Ethnicity (Somali Controls vs Patients With AMD)* Location No. Login to comment 133 ABCA4 p.Gly1961Glu ABCA4 p.Asp2177Asn Therefore, in this study, we focused on the 2 sequence variations (G1961E and D2177N) that were most plausibly associated with AMD in the study by Allikmets et al.7 In that study, Allikmets and colleagues found evidence that one or the other of those 2 sequence variations were found in approximately 8% of patients with AMD (one-half of the total ABCA4 association they observed). Login to comment 134 ABCA4 p.Gly1961Glu ABCA4 p.Gly1961Glu ABCA4 p.Asp2177Asn ABCA4 p.Asp2177Asn Although these 2 sequence variations were statistically associated with AMD when considered by themselves,7 there was no statistical association with AMD if all of the observed missense variations were included in the analysis, or alternatively, if all of the various subgroup analyses were subjected to a statistical correction for multiple measurements.16 In this study, we failed to find any statistically significant association between AMD and the presence of the G1961E and D2177N ABCA4 sequence variations. Login to comment 135 ABCA4 p.Gly1961Glu ABCA4 p.Asp2177Asn Although these 2 sequence variations were statistically associated with AMD when considered by themselves,7 there was no statistical association with AMD if all of the observed missense variations were included in the analysis, or alternatively, if all of the various subgroup analyses were subjected to a statistical correction for multiple measurements.16 In this study, we failed to find any statistically significant association between AMD and the presence of the G1961E and D2177N ABCA4 sequence variations. Login to comment 140 ABCA4 p.Gly1961Glu Her visual acuity was 20/200 OD. Although 5 of her 6 siblings harbored the G1961E allele, she did not. Login to comment 141 ABCA4 p.Gly1961Glu Her visual acuity was 20/200 OD. Although 5 of her 6 siblings harbored the G1961E allele, she did not. Login to comment 142 ABCA4 p.Gly1961Glu Although this woman did harbor the G1961E allele, the clinicians who examined her felt that she was unaffected by AMD. Login to comment 143 ABCA4 p.Gly1961Glu Although this woman did harbor the G1961E allele, the clinicians who examined her felt that she was unaffected by AMD. Login to comment 146 ABCA4 p.Gly1961Glu ABCA4 p.Asp2177Asn A plus indicates the presence of a heterozygous ABCA4 sequence variation that was present in the family`s proband (G1961E for family 1, and D2177N for families 2-5). Login to comment 147 ABCA4 p.Gly1961Glu ABCA4 p.Asp2177Asn A plus indicates the presence of a heterozygous ABCA4 sequence variation that was present in the family`s proband (G1961E for family 1, and D2177N for families 2-5). Login to comment 150 ABCA4 p.Gly1961Glu ABCA4 p.Asp2177Asn The sample size of this study was also large enough to result in a 95% power (␣=.05) to detect such a 3-fold difference if the frequency in the AMD cohort was as large as had been previously suggested (ie, 7.8% vs 2.6%).7 An interesting observation in the study by Allikmets and coauthors7 was that the G1961E and D2177N sequence variations were more commonly found in patients who had not experienced CNV. Login to comment 151 ABCA4 p.Gly1961Glu ABCA4 p.Asp2177Asn The sample size of this study was also large enough to result in a 95% power (a=.05) to detect such a 3-fold difference if the frequency in the AMD cohort was as large as had been previously suggested (ie, 7.8% vs 2.6%).7 An interesting observation in the study by Allikmets and coauthors7 was that the G1961E and D2177N sequence variations were more commonly found in patients who had not experienced CNV. Login to comment 153 ABCA4 p.Gly1961Glu ABCA4 p.Asp2177Asn Of the 12 patients with AMD in this study who harbor G1961E or D2177N sequence variations, 6 had CNV. Login to comment 154 ABCA4 p.Gly1961Glu ABCA4 p.Asp2177Asn Of the 12 patients with AMD in this study who harbor G1961E or D2177N sequence variations, 6 had CNV. Login to comment 157 ABCA4 p.Gly1961Glu For example, in this study, we found that the frequency of the G1961E allele was significantly higher in patients of Somali ancestry than in control populations from the United States, Australia, and Switzerland (Table 2) or AMD populations in the United States and Australia (Table 3). Login to comment 158 ABCA4 p.Gly1961Glu ABCA4 p.Gly1961Glu ABCA4 p.Gly1961Glu Although further work needs to be performed to carefully characterize the phenotype of G1961E heterozygotes with Somali ancestry, the point to be made in the present context is that Somali ancestry is more than 100 times more highly correlated to the presence of the G1961E sequence variation than the presence of AMD. Login to comment 159 ABCA4 p.Gly1961Glu ABCA4 p.Gly1961Glu Although further work needs to be performed to carefully characterize the phenotype of G1961E heterozygotes with Somali ancestry, the point to be made in the present context is that Somali ancestry is more than 100 times more highly correlated to the presence of the G1961E sequence variation than the presence of AMD. Login to comment 164 ABCA4 p.Asp2177Asn Her visual acuity in this eye was hand motions. She was found to harbor the D2177N allele. Login to comment 165 ABCA4 p.Asp2177Asn Her visual acuity in this eye was hand motions. She was found to harbor the D2177N allele. Login to comment 166 ABCA4 p.Asp2177Asn Her visual acuity in this eye was hand motions. She was found to harbor the D2177N allele. Login to comment 167 ABCA4 p.Asp2177Asn Her visual acuity in this eye was hand motions. She was found to harbor the D2177N allele. Login to comment 168 ABCA4 p.Asp2177Asn His visual acuity was 20/100 OS. Although 2 of his 3 relatives harbored the D2177N allele, he did not. Login to comment 169 ABCA4 p.Asp2177Asn His visual acuity was 20/100 OS. Although 2 of his 3 relatives harbored the D2177N allele, he did not. Login to comment 170 ABCA4 p.Asp2177Asn Her visual acuity was 20/100 OD. Although 2 of her 3 relatives harbored the D2177N allele, she did not. Login to comment 171 ABCA4 p.Asp2177Asn Her visual acuity was 20/100 OD. Although 2 of her 3 relatives harbored the D2177N allele, she did not. Login to comment 174 ABCA4 p.Gly1961Glu ABCA4 p.Asp2177Asn In the present study, we examined all of the siblings of 5 families affected with AMD who were also found to harbor a G1961E or D2177N ABCA4 allele. Login to comment 175 ABCA4 p.Gly1961Glu ABCA4 p.Asp2177Asn In the present study, we examined all of the siblings of 5 families affected with AMD who were also found to harbor a G1961E or D2177N ABCA4 allele. Login to comment 182 ABCA4 p.Gly1961Glu The fact that 11% of people of Somali ancestry are heterozygous for the G1961E allele would predict that more than 1% of that population would be homozygous. Login to comment 183 ABCA4 p.Gly1961Glu ABCA4 p.Gly1961Glu The fact that Stargardt disease is not known to be 100 times more prevalent in this population than in the United States, Switzerland, or Australia suggests that G1961E does not frequently cause disease in the homozygous state. Login to comment 184 ABCA4 p.Gly1961Glu ABCA4 p.Gly1961Glu It raises the testable hypothesis that G1961E is more likely to cause disease in the compound heterozygous state than in the homozygous state. Login to comment 185 ABCA4 p.Gly1961Glu ABCA4 p.Gly1961Glu Thus at the present time, it seems that we do not fully understand the pathogenic role of the G1961E allele even in patients with Stargardt disease (with which the allele has been significantly associated in multiple studies). Login to comment 186 ABCA4 p.Gly1961Glu Thus at the present time, it seems that we do not fully understand the pathogenic role of the G1961E allele even in patients with Stargardt disease (with which the allele has been significantly associated in multiple studies). Login to comment