Analysis of aPKCλ and aPKCζ reveals multiple and redundant functions during vertebrate retinogenesis

Retinal lamination is known to depend on cell polarity and localized signaling. In vertebrates, atypical protein kinase C proteins, aPKCλ/ι and aPKCζ, are essential for apical–basal cell polarity. However, it is not known to what extent functional redundancy has precluded a comprehensive functional characterization of aPKC signaling during vertebrate retinogenesis. Here, we show that aPKCs λ and ζ are functionally redundant for multiple aspects of retinogenesis including mitotic division location and orientation, cell-type positioning, and retinal pigment epithelial (RPE) and photoreceptor cell morphogenesis. Genetic mosaic analyses demonstrate a cell-autonomous requirement of aPKCs for RPE and photoreceptor development, and a cell-non-cell-autonomous function that is intrinsic to the neural retina for cell-type positioning. Our observations uncover a previously unappreciated involvement of aPKCζ during zebrafish retinogenesis and suggest that aPKC signaling primes the retinal environment for appropriate cell migration of post-mitotic progenitor cells but is not essential for correct cell-type specification.