Receptor protein tyrosine phosphatases regulate retinal ganglion cell axonoutgrowth in the developing Xenopus visual system

Receptor protein tyrosine phosphatases (RPTPs) are regulators of axon outgr owth and guidance in a variety of different vertebrate and invertebrate sys tems. Three RPTPs, CRYP-alpha, PTP-delta, and LAR, are expressed in overlap ping but distinct patterns in the developing Xenopus retina, including expr ession in retinal ganglion cells (RGCs) as they send axons to the tectum (J ohnson KG, Holt CE. 2000. Expression of CRYP-alpha, LAR, PTP-delta, and PTP -rho in the developing Xenopus visual system. Mech Dev 92:291-294). In orde r to examine the role of these RPTPs in visual system development, putative dominant negative RPTP mutants (CS-CRYP-alpha, CS-PTP-delta, and CS-LAR) w ere expressed either singly or in combination in retinal No effect was foun d on either retinal cell fate determination or on gross RGC axon guidance t o the tectum. However, expression of these CS-RPTP constructs differentiall y affected the rate of RGC axon outgrowth. In vivo, expression of all three CS-RPTPs or CS-PTP-delta alone inhibited RGC axon outgrowth, while CS-LAR and CS-CRYP-alpha had no significant effect. In vitro, expression of CS-CRY P-alpha enhanced neurite outgrowth, while CS-PTP-delta inhibited neurite ou tgrowth in a substrate-dependent manner. This study provides the first in v ivo evidence that RPTPs regulate retinal axon outgrowth. (C) 2001 John Wile y & Sons, Inc.