*5.7. RPGRIP1*

Retinitis pigmentosa GTPase regulator-interacting protein 1 (RPGRIP1) localizes to the connecting cilium, where it interacts with RPGR. Mutations in *RPGRIP1* are associated with autosomal recessive LCA. A cone–rod dystrophy form of PRA in a colony of miniature longhaired Dachshunds was reported to be due to an insertion in *Rpgrip1* [115] and the rescue of the phenotype by gene therapy was achieved [116]. When miniature longhaired Dachshunds in pet homes were investigated, the *Rpgrip1* insertion did not appear to segregate with disease status [117]. Further studies have shown that two other loci influence the development of the phenotype [118–120]. This is an example of the potential effect of modifying loci on phenotype.
