C2orf71a/pcare1 is important for photoreceptor outer segment morphogenesis and visual function in zebrafish

Mutations in C2orf71 are causative for autosomal recessive retinitis pigmentosa and occasionally cone-rod dystrophy. We have recently discovered that the protein encoded by this gene is important for modulation of the ciliary membrane through the recruitment of an actin assembly module, and have therefore renamed the gene to PCARE (photoreceptor cilium actin regulator). Here, we report on the identification of two copies of the c2orf71/pcare gene in zebrafish, pcare1 and pcare2. To study the role of the gene most similar to human PCARE, pcare1, we have generated a stable pcare1 mutant zebrafish model (designated pcare1 ^{rmc100/rmc100} ) in which the coding sequence was disrupted using CRISPR/Cas9 technology. Retinas of both embryonic (5 dpf) and adult (6 mpf) pcare1 ^{rmc100/rmc100} zebrafish display a clear disorganization of photoreceptor outer segments, resembling the phenotype observed in Pcare^-/- mice. Optokinetic response and visual motor response measurements indicated visual impairment in pcare1 ^{rmc100/rmc100} zebrafish larvae at 5 dpf. In addition, electroretinogram measurements showed decreased b-wave amplitudes in pcare1 ^{rmc100/rmc100} zebrafish as compared to age- and strain-matched wild-type larvae, indicating a defect in the transretinal current. Altogether, our data show that lack of pcare1 causes a retinal phenotype in zebrafish and indicate that the function of the PCARE gene is conserved across species.