Expression of receptor tyrosine phosphatases during development of the retinotectal projection of the chick

Receptor tyrosine kinases and receptor protein tyrosine phosphatases (RPTPs) appear to coordinate many aspects of neural development, including axon growth and guidance. Here, we focus on the possible roles of RPTPs in the developing avian retinotectal system. Using both in situ hybridization analysis and immunohistochemistry, we show for the first time that five RPTP genes—CRYPα, CRYP‐2, PTPμ, PTPγ, and PTPα—have different but overlapping expression patterns throughout the retina and the tectum. PTPα is restricted to Muller glia cells and radial glia of the tectum, indicating a possible function in controlling neuronal migration. PTPγ expression is restricted to amacrine neurons. CRYPα and CRYP‐2 mRNAs in contrast are expressed throughout the retinal ganglion cell layer from where axons grow out to their tectal targets. PTPμ is expressed in a subset of these ganglion cells. CRYPα, CRYP‐2, and PTPμ proteins are also localized in growth cones of retinal ganglion cell axons and are present in defined laminae of the tectum. Thus, the spatial and temporal expression of three distinct RPTP subtypes—CRYPα, CRYP‐2, and PTPμ—are consistent with the possibilty of their involvement in axon growth and guidance of the retinotectal projection. © 1999 John Wiley & Sons, Inc. J Neurobiol 39: 81–96, 1999