Zebrafish N-cadherin, encoded by the glass onion locus, plays an essential role in retinal patterning.

Genetic screens in zebrafish identified several loci that play essential roles in the patterning of retinal architecture. Here, we show that one of them, glass onion, encodes the N-cadherin gene. The glo(m117) mutant allele contains a substitution of the Trp2 residue known for its essential role in the adhesive properties of classic cadherins. Both the glo(m117) and pac(tm101b) mutant N-cadherin alleles affect the polarity of the retinal neuroepithelial sheet and, unexpectedly, both result in cell-nonautonomous phenotypes in retinal patterning. The late onset of mutant N-cadherin phenotypes may be due to the ability of classic cadherins to substitute each other's function.