PRPF31 - Inheritance

Inheritance

Mutations in PRPF31 are inherited in an autosomal dominant manner, accounting for 2.5% of cases of autosomal dominant retinitis pigmentosa (adRP) in a mixed UK population. However, the inheritance pattern of PRPF31 mutations is atypical of dominant inheritance, showing the phenomenon of partial penetrance, whereby a dominant mutations appear to "skip" generations. This is thought to be due to the presence of two wild type alleles, a high-expressivity allele and a low-expressivity allele. If a patient has a mutant allele and a high-expressivity allele, they do not show disease phenotype. If a patient has a mutant allele and a low-expressivity allele, the residual level of protein falls beneath the threahold for normal function, and so they do show disease phenotype. The inheritance pattern of PRPF31 can therefore be thought of as a variation of haploinsufficiency. This variant of haploinsufficiency is only seen in two other human diseases: Erythropoietic protoporphyria, caused by mutations in the FECH gene; and hereditary elliptocytosis, caused by mutations in the spectrin gene.