Abstract
PURPOSE: To examine the molecular genetic basis and phenotypic characteristics of an unusual late-onset autosomal dominant macular dystrophy with features of age-related macular degeneration (AMD) in a large family (SUNY901), by using linkage and mutation analyses. METHODS: Blood samples were collected from 17 affected members, 17 clinically unaffected members, and 5 unrelated spouses. Clinical analyses included a review of medical history and standard ophthalmic examination with fundus photography, fluorescein angiography, and electroretinography. Linkage and haplotype analyses were performed with microsatellite markers. Mutation analysis was performed by amplification of exons followed by sequencing. RESULTS: A wide spectrum of clinical phenotypes including exudative and nonexudative maculopathy was observed, with onset in the late fifth decade. Linkage analysis excluded most of the previously known maculopathy loci. Markers D6S1604 (Z(max) of 3.18 at theta = 0), and D6S282 (Z(max) of 3.18 at theta = 0) gave significant positive LOD scores and haplotype analysis localized the disease gene to a 9-centimorgan (cM) interval between markers D6S1616 and D6S459. Mutation analysis excluded the GUCA1A and GUCA1B genes and revealed a missense mutation in the RDS/peripherin gene leading to a Tyr141Cys substitution. A phenotype and haplotype comparison between this and a separate family with the Tyr141Cys mutation suggested the presence of a common ancestral haplotype. CONCLUSIONS: The RDS mutation in codon 141 is associated with an unusual AMD-like late-onset maculopathy. An apparent selective bias was noted favoring the transmission of the mutant allele. These observations broaden the spectrum of phenotypes associated with RDS gene mutations.