Transforming Growth Factor β Signal Transducer Smad2 Is Expressed in Mouse Meiotic Germ Cells, Sertoli Cells, and Leydig Cells During Spermatogenesis

Although previous studies have shown that members of the transforming growth factor b (TGFb) family are expressed in the seminiferous tubules, the functions of these growth factors in spermatogenesis remain elusive. In order to shed light on the mechanisms of TGFb action in spermatogenesis, it is crucial to determine whether and where their downstream signaling molecules are expressed in the testis. We examined the expression of Smad2, an intracellular signal transducer of the TGFbs, in mouse testes by in situ hybridization and immunohistochemistry. Both Smad2 mRNA and protein were detected in meiotic germ cells, from preleptotene to pachytene spermatocytes, but not in postmeiotic germ cells. Smad2 expression was also observed in interstitial cells and Sertoli cells. Therefore, our data provide molecular evidence for TGFb signal transduction during spermatogenesis.