ABCR Gene Analysis in Familial Exudative Age-Related Macular Degeneration

Identification of genetic factors in the pathogenesis of age-related macular degeneration (AMD) is of crucial importance in this common cause of blindness. Mutations in the Stargardt disease gene (ABCR) were previously reported in patients with atrophic forms of AMD. The purpose of this study was to analyze familial segregation of ABCR gene mutations in 52 unrelated multiplex cases of exudative AMD. A complete ophthalmological examination including visual acuity measurement, fundus examination, and fluorescein angiography (FA) was performed on each exudative AMD patient. The entire coding sequence of the ABCR gene was analyzed using a combination of single-strand conformation polymorphism and confirmatory sequencing of the exons showing an abnormal pattern of migration. Six heterozygous missense changes were identified. A lack of familial segregation was observed in 4 of 6 codon changes (Arg943Gln, Val1433Ile, Pro1948Leu, and Ser2255Ile). Conversely, 2 codon changes cosegregated with the disease in 2 small families: Pro940Arg and Leu1970Phe. The authors believe that segregation of the ABCR gene mutations with familial cases of AMD has not yet been shown. The analysis of familial segregation allowed the authors to exclude 4 of 6 codon changes as disease-causing mutations. Furthermore, it was shown here that the ABCR gene may be rarely involved in exudative AMD, with at best 2 of 52 familial cases (4%) related to this susceptibility factor.