Knockout of Bbs10 results in lack of cone electrical function and progressive retinal degeneration of rods and cones

Bardet Biedl Syndrome (BBS) is an autosomal recessive disorder caused by mutations in at least 22 different genes. A constant feature is early onset retinal degeneration leading to blindness, with variable central obesity, polydactyly, renal failure, and developmental anomalies. BBS type 10 (BBS10) is a common form caused by mutations in the BBS10 gene encoding a chaperonin-like protein. There are currently no treatments for the progressive vision loss. To aid in treatment development, a BBS10 mouse model was developed by knocking out the Bbs10 gene. Using optical coherence tomography (OCT), electroretinography (ERG), and a visually guided swim assay (VGSA), we demonstrate that Bbs10-/- mice have progressive retinal degeneration. Cone electrical function was absent although cones were anatomically present on histology and retained partial function based on VGSA. The retinal outer nuclear layer (photoreceptor nuclei) progressively thinned as demonstrated on OCT and histology, and rod electrical activity decreased over time on ERG. These phenotypes are more rapidly progressive than retinal degeneration in the Bbs1M390R/M390R knock-in mouse. They are consistent with a cone-rod dystrophy distinct from typical rod-cone degeneration in retinitis pigmentosa and recapitulate aspects of retinal degeneration observed in humans with BBS10. This study has implications for BBS10 gene therapy.