Loss of Crb2b-lf leads to anterior segment defects in old zebrafish.

Defects in the retina or the anterior segment of the eye lead to compromised vision and affect millions of people. Understanding how these ocular structures develop and are maintained is therefore of paramount importance. The maintenance of proper vision depends, among other factors, on the function of genes controlling apico-basal polarity. In fact, mutations in polarity genes are linked to retinal degeneration in several species, including human. Here we describe a novel zebrafish allele ( ), which specifically affects the long isoform. mutants are viable and display normal ocular development. However, old mutant fish develop multiple defects in structures of the anterior segment, which includes the cornea, the iris and the lens. Phenotypes are characterised by smaller pupils due to expansion of the iris and tissues of the iridocorneal angle, an increased number of corneal stromal keratocytes, an abnormal corneal endothelium and an expanded lens capsule. These findings illustrate a novel role for in the maintenance of the anterior segment and hence add an important function to this polarity regulator, which may be conserved in other vertebrates including humans.