Molecular cloning and characterization of a protein tyrosine phosphatase enriched in testis, a putative murine homologue of human PTPMEG

Protein tyrosine phosphorylation is regulated by protein tyrosine kinase an d protein tyrosine phosphatase activities. These two counteracting proteins are implicated in cell growth and transformation. Using polymerase chain r eaction with degenerate primers, we have identified a novel mouse protein t yrosine phosphatase (PTP). This cDNA contains a single open reading frame o f the predicted 926 amino acids. Those predicted amino acids showed signifi cant identity with human megakaryocyte protein-tyrosine phosphatase by 91% in nucleotide sequences and 94% in amino acid sequences. We have identified that expression of this PTP is highly enriched in the testis in mouse and human and has been termed here as a 'testis-enriched phosphatase' (TEP). No rthern analysis detected two mRNA species of 3.7 and 3.2 kb for this PTP in mouse testis and the expression of TEP is regulated during development. Th e recombinant phosphatase domain possesses protein tyrosine phosphatase act ivity when expressed in Escherichia coil. Immunohistochemical analysis of t he cellular localization of TEP on mouse testis sections showed that this P TP is specifically expressed in spermatocytes and spermatids within seminif erous tubules, suggesting an important role in spermatogenesis. (C) 2000 El sevier Science B.V. All rights reserved.