Rat osteotesticular phosphatase gene (Esp): genomic structure and chromosome location

Osteotesticular phosphatase (OST-PTPase) is a class III receptor-type tyros ine phosphatase (RPTPase). It has 10 tandem fibronectin III-like (FN-III) r epeats in the extracellular region and two phosphatase domains in the intra cellular region. The expression of the rat OST-PTPase gene, Esp, is restric ted to osteoblasts and Sertoli cells, and the transcript level in osteoblas ts is highly up-regulated by parathyroid hormone and cAMP treatment. We rep ort here the cloning and characterization of the rat Esp gene, including a 2.9-kb 5' Banking region sequence. Two potential binding sites for Osf2/Cbf a1, an osteoblast-specific transcription factor, are present in the promote r. Esp is composed of 35 exons, but spans merely 20 kb, making it the most compact RPTPase gene identified. Each FN-m repeat is encoded by a single ex on flanked with phase 1 introns. Two phosphatase domains are encoded by 16 exons in a genomic organization similar to those in RPRP alpha, RPTP gamma, and Ptprc genes. Esp was mapped by fluorescence in situ hybridization to r at chromosome 13q1. These results represent the first genomic structure of a mammalian class III RPTPase gene.