RPTPδ and the novel protein tyrosine phosphatase RPTPψ are expressed in restricted regions of the developing central nervous system

Transmembrane receptor-type protein tyrosine phosphatases (RPTPs) form a novel and potentially important class of cell regulatory proteins. To identify RPTPs expressed during neural development we have characterized RPTPs transcribed in embryonic day (E)13.5 rat neural tube. Nine different phosphatases, one of which was novel, were identified. We examined the expression of the novel phosphatase, called RPTPψ, and of two other phosphatases, RPTPδ and RPTPμ, whose expression in the developing nervous system has not yet been described in detail. The expression of RPTPμ in small blood capillaries in developing neural tissue is consistent with an involvement in angiogenesis. In contrast, the temporally and spatially regulated expression of RPTPψ and RPTPδ in neuroepithelium suggests a role in early neural development. In the spinal cord, early expression of RPTPδ in the roof plate is followed by its expression in differentiating motor neurons. RPTPψ mRNA is also transiently detectable in the roof plate as well as in floor plate cells. In the telencephalon as well as in the hind-brain at E13.5, the reciprocal expression patterns of RPTPδ and RPTPψ are consistent with a sequential function, RPTPψ exerting its activity in undifferentiated progenitor cells and RPTPδ functioning during neuronal differentiation. Dev Dyn 208:48–61, 1997.