*5.5. NPHP5 (IQCB1)*

A mutation was identified in the *NPHP5* gene (aka *IQCB1*) resulting in a cone–rod dystrophy in American pit bull terrier dogs (*crd2*) modeling non-syndromic LCA. This mutation (c.952-953insC, p.Ser319IlefsTer13) results in a frameshift and a premature stop codon [52]. At 6 weeks of age, the *crd2* dogs had no cone function and abnormal rod function. Morphologically, the cones completely lacked outer segments, while the rods developed disorganized outer segments. Despite the lack of cone function, the cones are retained within the central retina up to 33 weeks of age [106]. Adeno-associated gene therapy restores and improves photoreceptor function and preserves the outer retina layer [107].
