Organization and chromosomal localization of the murine Testisin gene encoding a serine protease temporally expressed during spermatogenesis

The recently characterized human serine protease, Testisin, is expressed on premeiotic testicular germ cells and is a candidate type II tumor suppress or for testicular cancer. Here we report the cloning, characterization and expression of the gene encoding mouse Testisin, Prss21. The murine Testisin gene comprises six exons and five introns and spans approximate to 5 kb of genomic DNA with an almost identical structure to the human Testisin gene, PRSS21. The gene was localized to murine chromosome 17 A3.3-B; a region sy ntenic with the location of PRSS21 on human chromosome 16p13.3. Northern bl ot analyses of RNA from a range of adult murine tissues demonstrated a 1.3 kb mRNA transcript present only in testis. The murine Testisin cDNA shares 65% identity with human Testisin cDNA and encodes a putative pre-pro-protei n of 324 amino acids with 80% similarity to human Testisin. The predicted a mino-acid sequence includes an N-terminal signal sequence of 27 amino acids , a 27 amino-acid pro-region, a 251 amino-acid catalytic domain typical of a serine protease with trypsin-like specificity, and a C-terminal hydrophob ic extension which is predicted to function as a membrane anchor. Immunosta ining for murine Testisin in mouse testis demonstrated specific staining in the cytoplasm and on the plasma membrane of round and elongating spermatid s. Examination of murine Testisin mRNA expression in developing sperm confi rmed that the onset of murine Testisin mRNA expression occurred at approxim ate to day 18 after birth, corresponding to the appearance of spermatids in the testis, in contrast to the expression of human Testisin in spermatocyt es. These data identify the murine ortholog to human Testisin and demonstra te that the murine Testisin gene is temporally regulated during murine sper matogenesis.