A Novel Testis-Specific Metallothionein-like Protein,Tesmin,Is an Early Marker of Male Germ Cell Differentiation

We have cloned a novel cDNA encoding testis-specific metallothionein-like protein,tesmin,by randomized RT-PCR on RNA from mouse tissues. Twotesmin-related transcripts (2.2 and 1.8 kb) in mouse and one (2.1 kb) in human were detected and cloned. These encode a cysteine-rich 32-kDa protein that contained a metallothionein-like motif.In situhybridization analysis in adult mouse testis showed thattesminis specifically expressed in spermatocytes. Quantitative RT-PCR at different stages of mouse postnatal development (days 4, 8, 12, 18, and 42) revealed thattesminis expressed as early as day 8 and coincides with the entry of germ cells into meiosis. Furthermore, adult W/Wvsterile mice that harbor the c-kitmutation lackedtesminexpression. The gene is assigned to mouse chromosome 19B, which has been reported to translocate (11;19) in male sterile mice.