Expression of receptor protein tyrosine phosphatases in embryonic chick spinal card

Receptor-like protein tyrosine phosphatases potentially play a crucial role in axon growth and targeting. We focus here on their role within the embry onic avian spinal cord, in particular the development and outgrowth of moto rneurons. We have used in situ mRNA hybridization to examine the spatiotemp oral expression of eight receptorlike protein tyrosine phosphatases and fin d that it is both dynamic and highly varied, including novel, isoform-speci fic expression patterns. CRYP alpha1 is expressed in all of the ventral mot orneuron pools, whereas CRYP2, RPTP gamma, and RPTP alpha are only expresse d in specific subsets of these neurons. CRYP alpha2, RPTP Psi, and RPTP del ta are neuronally expressed elsewhere in the cord, but not in ventral motor neurons, whereas RPTP mu is unique in being restricted to capillaries. The developmentally regulated, expression of these genes strongly suggests that the encoded phosphatases play numerous roles during neurogenesis and axono genesis in the vertebrate spinal cord.