Receptor protein tyrosine phosphatases (RPTPs) are regulators of axon outgrowth and guidance in a variety of different vertebrate and invertebrate systems. Three RPTPs, CRYP-α, PTP-δ, and LAR, are expressed in overlapping but distinct patterns in the developing Xenopus retina, including expression in retinal ganglion cells (RGCs) as they send axons to the tectum (Johnson 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 order to examine the role of these RPTPs in visual system development, putative dominant negative RPTP mutants (CS-CRYP-α, CS-PTP-δ, and CS-LAR) were expressed either singly or in combination in retinal cells. No effect was found on either retinal cell fate determination or on gross RGC axon guidance to the tectum. However, expression of these CS-RPTP constructs differentially affected the rate of RGC axon outgrowth. In vivo, expression of all three CS-RPTPs or CS-PTP-δ alone inhibited RGC axon outgrowth, while CS-LAR and CS-CRYP-α had no significant effect. In vitro, expression of CS-CRYP-α enhanced neurite outgrowth, while CS-PTP-δ inhibited neurite outgrowth in a substrate-dependent manner. This study provides the first in vivo evidence that RPTPs regulate retinal axon outgrowth.

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Keywords Guidance, Outgrowth, Retina, RPTP, Tectum
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Journal Journal of Neurobiology
Johnson, K.G. (Karl G.), McKinnell, I.W, Stoker, A.W. (Andrew W.), & Holt, C.E. (Christine E.). (2001). Receptor protein tyrosine phosphatases regulate retinal ganglion cell axon outgrowth in the developing Xenopus visual system. Journal of Neurobiology, 49(2), 99–117. doi:10.1002/neu.1068