Identification of a receptor-like protein tyrosine phosphatase expressed during Xenopus development

To begin to determine the role of receptor-like tyrosine phosphatases during Xenopus development, we have isolated a cDNA predicted to encode receptor-like tyrosine phosphatase with significant amino acid sequence identity to mouse and human protein tyrosine phosphatase alpha (PTPalpha). Xenopus PTPalpha (XPTPalpha) exists as a maternally expressed mRNA that decreases in expression during gastrulation and then maintains a constant lower level of expression through early tadpole stages. In situ hybridization reveals that XPTPalpha mRNA is expressed throughout the gastrula stage embryo. During subsequent development, XPTPalpha mRNA becomes restricted in its expression to various regions of the brain and the visceral arches. XPTPalpha mRNA is also expressed in several adult tissues and in Xenopus XTC cells. Immunoblot analysis demonstrates that XPTPalpha protein is expressed at relatively uniform levels throughout development. Expression of XPTPalpha protein in insect cells with a recombinant baculovirus results in a glycosylated polypeptide of 110-130 kDa with intrinsic phosphotyrosine phosphatase activity. The spatial and temporal patterns of expression of XPTPalpha indicate that it may play multiple roles during early development including development of the brain.