RPE65 – Leber Congenital Amaurosis

RPE65 encodes the retinal pigment epithelium–specific 65 kDa protein that serves as the isomerohydrolase converting all-trans retinyl esters to 11-cis retinol in the visual cycle. Biallelic pathogenic variants in RPE65 lead to Leber congenital amaurosis (LCA), the most severe early-onset form of inherited retinal dystrophy, characterized by congenital visual impairment, nonrecordable electroretinograms, and progressive photoreceptor loss. RPE65 expression in the RPE is critical for chromophore regeneration and sustained rod and cone function.

Multiple studies have established an autosomal recessive inheritance pattern, with over 20 unrelated probands from more than 10 families harboring compound heterozygous or homozygous RPE65 mutations (PMID:9326941)(PMID:14962443). Segregation analysis in sibships from North America and Yemen confirmed cosegregation of biallelic loss-of-function alleles with LCA (PMID:24771178). Heterozygous carriers remain asymptomatic, reaffirming recessive inheritance.

Genetic screening has uncovered a spectrum of RPE65 variants including nonsense, frameshift, splice-site, and missense changes. Loss-of-function alleles predominate, with recurrent founder and population-specific variants such as c.304G>T (p.Glu102Ter) identified in diverse cohorts (PMID:15512997). Deep-intronic and hypomorphic mutations have also been reported, contributing to variable phenotypic severity and age of onset.

Functional assays confirm that RPE65 is the key isomerohydrolase in the visual cycle; recombinant RPE65 catalyzes 11-cis retinol formation only when coexpressed with lecithin retinol acyltransferase (PMID:16116091). Missense mutations of active-site residues abolish enzymatic activity, while variants at non-active sites reduce protein stability, mislocalize RPE65, and impair isomerohydrolase function (PMID:16150724)(PMID:16828753).

Animal and cellular rescue studies underpin therapeutic relevance: subretinal lentiviral or AAV-mediated RPE65 gene transfer restores retinal function, preserves cones, and halts degeneration in Rpe65-deficient mice and canine models (PMID:17032058). Moreover, the D477G allele demonstrates autosomal dominant retinitis pigmentosa with choroidal involvement, highlighting allelic heterogeneity beyond recessive LCA (PMID:32014860).

Integrating genetic and experimental data, RPE65-associated LCA meets criteria for a Definitive gene–disease relationship, with strong genetic segregation, a preclinical isomerohydrolase mechanism, and successful in vivo rescue. Comprehensive variant characterization is essential for precise molecular diagnosis, prognosis, and eligibility for voretigene neparvovec or other emerging gene therapies. Key take-home: RPE65 mutation testing enables definitive LCA diagnosis and directs life-changing gene augmentation therapy.

References

• Nature Genetics • 1997 • Mutations in RPE65 cause autosomal recessive childhood-onset severe retinal dystrophy. PMID:9326941
• American Journal of Ophthalmology • 2004 • Thirty-year follow-up of a patient with leber congenital amaurosis and novel RPE65 mutations. PMID:14962443
• Klinische Monatsblätter für Augenheilkunde • 2014 • Cone-rod dystrophy caused by a novel homozygous RPE65 mutation in Leber congenital amaurosis. PMID:24771178
• Proceedings of the National Academy of Sciences of the USA • 2005 • RPE65 is the isomerohydrolase in the retinoid visual cycle. PMID:16116091
• Proceedings of the National Academy of Sciences of the USA • 2005 • Mutation of key residues of RPE65 abolishes its enzymatic role as isomerohydrolase in the visual cycle. PMID:16150724
• FEBS Letters • 2006 • Impacts of two point mutations of RPE65 from Leber's congenital amaurosis on the stability, subcellular localization and isomerohydrolase activity of RPE65. PMID:16828753
• PLoS Medicine • 2006 • Lentiviral gene transfer of RPE65 rescues survival and function of cones in a mouse model of Leber congenital amaurosis. PMID:17032058
• Cold Spring Harbor Molecular Case Studies • 2020 • Phenotypic expansion of autosomal dominant retinitis pigmentosa associated with the D477G mutation in RPE65. PMID:32014860

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