CADHERIN FUNCTION IS REQUIRED FOR AXON OUTGROWTH IN RETINAL GANGLION-CELLS IN-VIVO

The cell-cell adhesion molecule N-cadherin strongly promotes neurite o utgrowth in cultured retinal neurons. To test whether cadherins regula te process outgrowth in retinal neurons in vivo, we have blocked cadhe rin function in single cells by expression of a dominant negative N-ca dherin mutant. We report that when cadherin function is inhibited, axo n and dendrite outgrowth are severely impaired, particularly in retina l ganglion cells. Laminar migration and cell type specification, by co ntrast, appear unaffected. Further, expression of the catenin-binding domain of N-cadherin, which blocks cadherin-mediated adhesion in early embryos, does not affect axon outgrowth, suggesting that outgrowth an d adhesion are mediated by distinct regions of the cytoplasmic domain. These findings indicate that cadherins play an essential role in the initiation and extension of axons from retinal ganglion cells in vivo.