Seasonal variation in expression and localization of testicular transforming growth factors TGF-β1 and TGF-β3 corresponds with spermatogenic activity in roe deer

Adult roe deer males show hormonally controlled seasonal cycles of testicular growth and involution. Mediation of endocrine signals likely requires variable production of testicular growth factors for regulation of testis function. Here we studied the expression pattern of transforming growth factors (TGFs) beta 1 and beta 3. Total RNA from testis parenchyma was extracted monthly and analysed using quantitative reverse transcriptase PCR. The localization of mRNAs was determined by in situ hybridization, and corresponding proteins were visualized immunohistochemically. Both factors showed different expression levels and different seasonal expression patterns. The TGF-beta 1 mRNA content was up to 45 times higher than that of TGF-beta 3. Compared with its lowest level in May, TGF-beta 1 expression was slightly enhanced during pre-rut (June/July). TGF-beta 3 expression increased 5-fold from April to June/July and decreased thereafter to its low in December. This corresponded with changing numbers of spermatocytes and round spemiatids, in which both TGF-beta 3 mRNA and the protein were mainly localized. The TGF-beta 1 mRNA was found in interstitial cells, mainly during the non-breeding season, but also in spemiatocytes and spermatids during activated spermatogenesis. The translation product was localized in few spermatogenic cells only. The results suggest that TGF-beta 1 and -beta 3 are important in regulating seasonal spermatogenesis of roe deer with diverse functions affecting interstitial and spermatogenic cells.