Abstract
Abstract: :
Purpose: Arrestin 3 (syn.: x–arrestin, cone arrestin) is a Ca2+ binding protein that is presumed to contribute to desensitization and light adaptation of cone photoreceptors. In the light–adapted retina, arrestin 3 accumulates in the cone outer segments, presumably interacting with bleached (phosphorylated) cone visual pigments and quenching of the phototransduction cascade. In the dark, arrestin is located in the inner segment, but redistributes rapidly to the outer segment upon illumination. The gene encoding arrestin 3 (ARR3) is located on the X–chromosome, cen–q21, and therefore is considered a prime candidate gene for X–linked cone dystrophies. Methods: We selected 24 male patients with stationary cone photoreceptor dysfunctions in which mutations in the known achromatopsia genes (CNGA3, CNGB3, GNAT2) had already been excluded, as well as common mutations and rearrangements in the red–green opsin gene cluster. All coding exons with flanking intronic sequences and the established promoter region were analyzed by PCR from genomic DNA and direct DNA sequencing applying BigDye chemistry on an ABI 3100 DNA Sequencer. Observed sequence variations were evaluated in 100 healthy control subjects via PCR/RFLP assays. Results: Several known (one in the exon and three in the intron sequence) and unknown (three in the intron ) sequence alterations were observed. The unknown alterations were also detected in the control samples. Conclusions: To date, no disease causing mutations in the coding sequence of ARR3 have been identified. These data show that ARR3 mutations are not a major cause of cone dysfunction in males that lack mutations in genes associated with achromatopsia or blueconemonochromacy.
Keywords: candidate gene analysis • signal transduction • color vision