CELLULAR-DISTRIBUTION OF TRANSFORMING GROWTH-FACTOR BETA-1, BETA-2, AND BETA-3 AND THEIR TYPE-I AND TYPE-II RECEPTORS DURING POSTNATAL-DEVELOPMENT AND SPERMATOGENESIS IN THE BOAR TESTIS

Transforming growth factor betas (TCF beta s) 1, 2, and 3 and their ty pes I and II receptors (TCF beta s RI and RII) were immunolocalized 1) during testicular development from the perinatal to the adult period and 2) in maturing germ cell populations at successive seminiferous ep ithelium stages. In the perinatal testis, TGF beta isoforms and recept ors were both preponderant in Leydig cells and in spermatogonia. At pr epuberty, their expression appeared in Sertoli cells, while germ cells showed specific TGF beta 1 and TGF beta RI staining in the spermatocy tes. In the adult testis, TGF beta ligands exhibited a preferential tu bular distribution. TGF beta 1 was mainly detected in young spermatocy tes, TGF beta 2 in Sertoli cells, and TGF beta 3 in Sertoli and premei otic germ cells. Although the two receptors were systematically observ ed together in various cells, our data indicate a predominance of one in comparison with the other depending on the cell type. TGF beta RI w as predominant in meiotic and differentiated germ cells and TGF beta R II in somatic cells. Finally, in the adult testis, TCF beta s 1, 3, an d RI showed a germ-cell pattern that depended upon the stage of the se miniferous epithelium cycle. Specifically, staining for the ligands wa s predominant before meiosis, and TGF beta RI was present particularly during meiosis and spermiogenesis. Together, the temporal and spatial distribution of the TGF beta system components suggests that these si gnaling molecules may play a crucial role during specific steps of tes ticular development and during different waves of seminiferous epithel ium maturation leading to spermatogenesis.