Expression of prothymosin alpha in meiotic and post-meiotic germ cells during the first wave of rat spermatogenesis

Prothymosin alpha (PTMA) is a highly acidic small polypeptide, that is, widely distributed and conserved among mammals. Its possible involvement in male gametogenesis has been mentioned but not clarified yet; in particular, it has been suggested that, in non-mammalian vertebrates, it could play a role during GC meiosis and differentiation. In the present work we investigated the possible association between PTMA and meiotic and post-meiotic phases of mammalian spermatogenesis. Three different time points during postnatal development of rat testis were analyzed, that is, 27 dpp (completed meiosis), 35 dpp (occurring spermiogenesis), and 60 dpp (first wave of spermatogenesis definitely ended). RT-PCR and Western blot analyses showed that the expression levels of both Ptma mRNA and corresponding protein decrease in total extracts from 27 to 60 dpp. The in situ hybridization localized the transcript in interstitial Leydig cells, peritubular myoid cells and, inside the tubules, in germ cells from pachytene spermatocytes to newly formed haploid spermatids. The immunohistochemistry analysis localized the protein in the same cell types at 27 dpp, while at 35 and 60 dpp the haploid cells remain the only germ cells that still express it. In particular, PTMA specific localization in the heads of spermatids and epididymal spermatozoa, associated with the acrosome system, supports for the first time the hypothesis of a direct function in male germ cells.