Novel RPE65 mutations associated with Leber congenital amaurosis in Chinese patients

Retinal pigment epithelium-specific protein 65 kDa (RPE65) plays an essential role in vitamin A metabolism necessary for synthesizing the visual pigment 11-cis-retinal chromophore. Mutations in RPE65 cause the childhood blindness disorder known as Leber congenital amaurosis (LCA), as well as autosomal recessive retinitis pigmentosa (RP). The purpose of this study was to identify RPE65 mutations in Chinese patients with LCA, determine the prevalence of RPE65 mutations in this cohort, and assess the clinical features of those patients with RPE65 mutations.

Detailed ocular examinations were performed, and genomic DNA was isolated with standard methods for genetic diagnosis. All 14 exons of RPE65 were amplified with PCR and screened for mutation with direct DNA sequencing. Two hundred unrelated healthy Chinese subjects were screened to exclude nonpathogenic polymorphisms. Multiple alignments of eight eukaryotic RPE65 orthologs were performed.

A total of 101 LCA patients, drawn from 100 unrelated families, were selected for mutation screening in the RPE65 gene. Compound heterozygous missense mutations Leu67Arg and Tyr368Cys were identified in two affected sisters and segregated with their family. Four previously reported polymorphisms were identified in this study. No other disease-related mutation was detected. The frequency spectrum of variations in the RPE65 gene was estimated to be 1% (1/100) in this cohort of Chinese patients with LCA. The two patients showed classical signs of LCA with relatively preserved central vision and retinal structure.

The RPE65 mutation is a rare cause of LCA in the Chinese population. Compound heterozygous missense mutations Leu67Arg and Tyr368Cys are related to a relatively mild LCA phenotype. Genetic characterization of patients with RPE65 mutations is important for future rational therapies.