Loss of Nance-Horan Syndrome b (nhsb) prevents expansion growth of retinal progenitor cells by selective up-regulation of Δ113p53

The regulation of cell cycle progression and differentiation in retinal progenitor cells is a fundamental feature controlling organ size of the eye in vertebrates. Nance-Horan Syndrome (NHS) is a rare X-linked disorder caused by mutations in the NHS gene. Dysmorphic features of NHS include severe congenital cataracts, micropthalmia, facial dysmorphisms, and visual impairment. In this study we report an evolutionarily conserved role for NHS in vertebrate retinogenesis. Loss of function of nhs leads to small eye size in both zebrafish and Xenopus tropicalis, marked by reduced proliferation but not cell death. Transcriptome analysis of nhs morphant zebrafish eyes revealed a marked upregulation in Δ113p53, an isoform of p53, concomitant with a selective upregulation of p53 responsive genes that inhibit cell cycle progression but not apoptosis. Our data supports a model where Nhs is a negative regulator of Δ113p53 expression and exerts its function through regulation of the p53 pathway to promote expansive growth of retinal progenitor cells prior to differentiation.