Molecular cloning of the human homolog of a striatum-enriched phosphatase (STEP) gene and chromosomal mapping of the human and murine loci.

A gene for a protein tyrosine phosphatase (PTPase) was isolated from a human fetal brain cDNA library by PCR amplification. Sequence analysis revealed that the PTPase has a single phosphatase catalytic domain located at the C-terminus that includes the highly conserved amino acid domain [I/V]HCXAGXXR[S/T]GX[F/Y] found in all tyrosine phosphatases. Two proline-rich regions located at the N-terminus may contain putative Src homology domain 3 (SH3) binding motifs. Comparison of the PTPase with a previously cloned striatum enriched phosphatase (STEP) from rat and from mouse exhibited a high degree of identity (approximately 85-90%) at both the nucleotide and the amino acid levels, indicating that the human PTPase is the homolog of the rat and murine STEP gene. By using a combination of somatic cell hybrid analysis and fluorescence in situ hybridization, we have mapped the human STEP locus to chromosome 11p15.2-p15.1 and the murine STEP gene to chromosome 7B3-B5. These are two regions of known conserved synteny, providing further evidence that the human STEP is a true homolog of the murine STEP gene. Candidate disease genes in the vicinity include Usher syndrome type 1C in human and a mouse mutant locus, twister (twt).