A short N-terminal domain of HDAC4 preserves photoreceptors and restores visual function in retinitis pigmentosa

Retinitis pigmentosa is a leading cause of inherited blindness, with no effective treatment currently available. Mutations primarily in genes expressed in rod photoreceptors lead to early rod death, followed by a slower phase of cone photoreceptor death. Rd1 mice provide an invaluable animal model to evaluate therapies for the disease. We previously reported that overexpression of histone deacetylase 4 (HDAC4) prolongs rod survival in rd1 mice. Here we report a key role of a short N-terminal domain of HDAC4 in photoreceptor protection. Expression of this domain suppresses multiple cell death pathways in photoreceptor degeneration, and preserves even more rd1 rods than the full-length HDAC4 protein. Expression of a short N-terminal domain of HDAC4 as a transgene in mice carrying the rd1 mutation also prolongs the survival of cone photoreceptors, and partially restores visual function. Our results may facilitate the design of a small protein therapy for some forms of retinitis pigmentosa.