Analysis of the Stargardt disease gene (ABCR) in age-related macular degeneration

Purpose: Age-related macular degeneration (AMD) is a complex genetic disord er and the leading cause of severe vision loss in the elderly. The Stargard t disease gene (ABCR) has been proposed as a major genetic risk factor in A MD. The purpose of this study was to evaluate the authors' AMD population f or the specific ABCR variants proposed previously as genetic risk factors f or AMD. Methods: The authors screened their AMD population (159 familial cases from 112 multiplex families and 53 sporadic cases) and 56 racially matched indi viduals with no known history of AMD from the same clinic population for ev idence of the ABCR variants. Grading of disease severity was performed acco rding to a standard protocol. Patients with extensive intermediate drusen o r 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 chai n reaction amplification of individual exons of the ABCR gene with flanking primers and a combination of single-strand conformation polymorphism, hete roduplex analysis, and high-performance liquid chromatography. All abnormal conformers detected using these techniques were characterized by direct se quencing. Results: The authors identified only two of the previously reported variant s in their study population. Both variants occurred in sporadic cases, and none was found in familial cases or the randomly selected population. In ad dition, the authors identified several newly described polymorphisms and va riants 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. Addi tional genetic studies are needed to more fully evaluate the role of ABCR i n AMD.