Objective: To identify the gene causing retinitis pigmentosa (RP) in an autosomal dominant pedigree.
Methods: Family members with RP were studied with linkage analysis using single-nucleotide polymorphism and short tandem repeat polymorphic markers. Candidate genes in the linked region were evaluated with DNA sequencing.
Results: Nineteen family members had a mild form of RP. Multipoint linkage analysis of single-nucleotide polymorphism genotypes yielded a maximum nonparametric linkage score of 19.97 with markers located on chromosome 14q. LOD scores higher than 3.0 were obtained with 20 short tandem repeat polymorphic markers, and recombinants defined a 21.7-centimorgan locus on chromosome 14q. The retinol dehydrogenase 12 (RDH12) gene lies within this locus and was evaluated as a candidate gene. A frameshift mutation (776delG) was detected in all affected family members and was not detected in 158 control subjects.
Conclusions: Heterozygous mutations in RDH12 can cause autosomal dominant RP with a late onset and relatively mild severity. This phenotype is dramatically different from the other disease associated with mutation in this gene, autosomal recessive Leber congenital amaurosis.
Clinical relevance: The demonstration that mutations in a gene previously associated with recessive Leber congenital amaurosis can also cause dominant RP illustrates the wide phenotypic variability of retinal degeneration genes.