The receptor tyrosine phosphatase CRYP alpha affects growth cone morphology

During development of the nervous system receptor tyrosine kinases and rece ptor protein tyrosine phosphatases act in a coordinate way during a ion gro wth and guidance. In the developing avian retinotectal system, many differe nt receptor protein tyrosine phosphatases are expressed. Most of them have unknown functions, Retinal ganglion cells express at least three different members of this receptor family on their axons and growth cones: CRYP alpha , CRYP-2 and PTP mu. CRYP alpha interacts heterophilically with at least tw o different Ligands found in the basal membranes of the retina and the opti c tectum, To analyze the role of the CRYP alpha-ligand interaction, retinal ganglion cell axions were grown on retinal basal membranes (inner limiting membrane) and the receptor-ligand interaction was blocked from both the re ceptor side (by receptor specific antibodies) and from the ligand side by u sing a receptor-alkaline phosphatase fusion protein. Both of these treatmen ts reduced average retinal axon length and induced a dramatic change in mor phology of retinal ganglion cell growth cones on basal membranes, but not o n other substrates like laminin, N-cadherin, matrigel- and detergent-treate d basal membranes. These results suggest that CRYP alpha and its ligand act as growth-promoting molecules during intraretinal axon growth. (C) 2000 Jo hn Wiley & Sons, Inc.