Evidence for the involvement of Prothymosin alfa in the spermatogenesis of the frog Rana esculenta.

Prothymosin alpha (PTMA) is a small acidic protein abundantly and ubiquitously expressed in mammals and involved in different biological activities. Until now, its specific function in spermatogenesis has never been properly investigated. Recently, the isolation of a cDNA encoding for PTMA from the testis of the frog Rana esculenta has been reported: ptma transcript is highly expressed throughout the frog reproductive cycle, peaking in September/October, in concomitance with the germ cell maturation; it is specifically localized in the cytoplasm of primary and secondary spermatocytes and, at a lower level, in the interstitial compartment, in Leydig cells. In this article we support the involvement of PTMA in the meiotic phases of frog spermatogenesis. The expression of ptma mRNA increases in the testis of frogs treated with the antiandrogen cyproterone acetate, which blocks the II meiotic division and induces an increase in SPC cysts; on the contrary, it highly decreases in the testis of animals kept at 41C and treated with human corionic gonadotropin, in concomitance with the induced block of spermatogenesis and the disappearance of meiotic cells in the tubules. Furthermore, for the first time we have also evidenced by immunohistochemistry the expression of PTMA in the nuclei of secondary spermatocytes, spermatids, and spermatozoa, as well as in the cytoplasm of interstitial Leydig cells. Taken together our data suggest for an important role of PTMA in germ cell maturation and/or differentiation during R. esculenta spermatogenesis.