The mouse Tsx gene is expressed in Sertoli cells of the adult testis and transiently in premeiotic germ cells during puberty

Tsx is a gene of unknown function that was previously shown to be expressed specifically in the testis. In order to gain insight into the function of Tsx its pattern of expression was characterized with regard to both timing and cell type in the testis. Northern blot analysis of early postnatal test es showed not only that Tsx message was detectable shortly after birth, but that it increased substantially between 7 and 12 days postpartum (dpp), ro ughly coincident with the onset of meiosis in the mouse. Alternative Tsx tr anscripts, detected by RT-PCR, included a spliced form that first appeared at around 12 dpp. In situ hybridization revealed Tsx signal in the somatic Sertoli cells of the adult testis. Consistent with the data from Northern b lots, in situ hybridization signal was first detectable in normal pubertal testes at 12 dpp. An anti-Tsx polyclonal antiserum specifically stained pre meiotic germ cells in addition to Sertoli cells of pubertal testes at 16, 1 9, and 27 dpp. Tsx immunostaining in germ cells was nuclear, while Sertoli cells displayed signal throughout the cytoplasm and nucleus. In the adult, Tsx was detected exclusively in Sertoli cells. In contrast, in the adult te stis of the oligotriche (olt) mutant, where spermatogenesis is blocked afte r meiosis, Tsx protein was still present in the spermatogonial nuclei of a subset of tubules. Taken together, these results demonstrate that Tsx expre ssion is induced in both premeiotic germ cells and Sertoli cells during the first wave of spermatogenesis, but that expression is maintained at a dete ctable level only in Sertoli cells of the normal adult. The persistence of Tsx expression seen in spermatogonia of the adult olt mutant supports the h ypothesis that during the first wave of normal spermatogenesis, the advent of a late-stage cell type, either elongating spermatid or spermatozoan, is responsible for extinguishing expression in spermatogonia in normal adult t estis. To our knowledge, Tsx is the first gene to show a pattern of germ ce ll expression that is apparently specific to the pubertal testis. (C) 1998 Academic Press.