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Title: Receptor protein tyrosine phosphatases in the developing Xenopus visual system
Author: Johnson, K. G.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2000
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The aim of my research was to understand how RPTPs are involved in retinal ganglion cell (RGC) axon outgrowth and guidance in the development of the Xenopus visual system. I first describe the cloning and expression patterns of a variety of RPTPs in the developing Xenopus embryo, focusing on the retinotectal system. All three members of Type IIa RPTPs; LAR, PTP-δ, and CRYP-α, are expressed in RGCs during periods of differentiation, axonogenesis, and axon guidance from the retina to the tectum. These three RPTPs, as well as PTP-p, are expressed in overlapping but distinct patterns in the developing Xenopus embryo. Expression patterns of putative ligands for CRYP-α and LAR were examined using receptor affinity probe in situ hybridisation in the developing retina and brain, and putative ligands for CRYP-α were found along the optic pathway and in the tectum. These results demonstrate that Type IIa RPTPs and their putative ligands are expressed in a spatial and temporal pattern consistent with their involvement in RGC axon guidance and outgrowth from the retina to the tectum. I also describe functional studies examining the role of RPTPs in the developing Xenopus visual system both in vitro and in vivo. In vitro analysis of RGCs expressing dominant negative RPTPs demonstrates that dominant negative PTP-δ inhibits RGC axon outgrowth, while dominant negative CRYP-α promotes outgrowth, in a substrate-dependent manner. In vivo analysis of RGC axon outgrowth and guidance demonstrates that although dominant negative PTP-δ and LAR reduce the rate of axon outgrowth, none of these RPTPs appear to be involved in axon guidance.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available