Expression and regulation of transcription factors GATA-4 and GATA-6 in developing mouse testis

Previous studies have shown that transcription factors GATA-4 and GATA-6 ar e expressed in granulosa and thecal cells of the mouse ovary and that GATA- 4 expression in ovarian tissue is regulated by gonadotropins. Given the eme rging role of GATA-4 and GATA-6 in gonadal cells, we have now studied the e xpression and regulation of these factors in the mouse testis and testicula r cell lines. In situ hybridization demonstrated GATA-4 messenger RNA (mRNA ) in the fetal testis at 13.5 days postcoitum. Both GATA-4 and GATA-6 trans cripts were observed in late fetal, neonatal, juvenile, and adult Sertoli c ells. In addition, GATA-4 mRNA was detected in interstitial cells throughou t development. Immunohistochemistry demonstrated GATA-4 protein in both Ser toli and Leydig cells in postnatal animals. The regulation of GATA-4 and GA TA-6 expression was explored using established testicular cell lines. Treat ment of Leydig tumor cell lines with hCG resulted in a modest, but statisti cally significant, increase in the steady state level of GATA-4 mRNA, compa rable to the previously described effect of FSH on GATA-4 expression in Ser toli cell lines. Gonadotropin or androgen action was not, however, a prereq uisite for the basal expression of GATA-4 or GATA-6 in the testis, as their presence in Sertoli and Leydig cells was demonstrated in genetically hypog onadal hpg mice, in rats treated with GnRH receptor antagonist, and in Sert oli cells after chemical abolition of Leydig cells. Cotransfection studies using a GATA-4 expression plasmid and an inhibin alpha promoter/reporter ge ne construct in Leydig and granulosa tumor cell lines revealed that the inh ibin alpha promoter harboring essential GATA-binding sites can be trans-act ivated by GATA-4. In light of these results, we propose that transcription factors GATA-4 and GATA-6 play differing roles in the maturation and functi on of testicular somatic cells.