Proteome analysis of rat spermatogonia: Reinvestigation of stathmin spatio-temporal expression within the testis

Stathmin is a protein known to be involved in various cell processes includ ing cell proliferation and differentiation. It has already been described i n the testis but its recent identification using a proteomic approach in mi totic spermatogenetic stem cells named spermatogonia (Guillaume et al., 200 0) has lead us to reinvestigate its expression within the testis. Stathmin and its mRNAs were studied in isolated cells by Western and Northern blots and in situ using immunohistochemistry. We demonstrated that stathmin is in deed expressed in spermatogonia, and that it is also intensively expressed in the meiotic spermatocytes and in the first generations of spermatids. Fu rthermore, we showed aggregations of the protein in the cytoplasm of the la ter generations of spermatids preceding its elimination at the time of sper miation. Our Northern blots reveal the presence of two stathmin transcripts of 1.1 and 3.2 kb within the testis from the fetal stage onwards, in sperm atogonia, spermatocytes, and spermatids. However, the 3.2 kb RNA transcript was barely detectable in the spermatids. Stathmin expression is known to b e associated with microtubule dynamics. Therefore, its expression in the ge rm line is most probably related to the extremely complex structural cellul ar rearrangements occurring in germ cells during spermatogenesis. However, the exact role of stathmin and the reason of the existence of two transcrip ts in the male germ lineage awaits further investigation. Mol. Reprod. Dev. 60: 439-445, 2001. (C) 2001 Wiley-Liss, Inc.