Function Study Of Flotillin-2during Mouse Spermiogenesis

Spermatogenesis is a complex process of terminal differentiation to generatemature sperm, and it can be divided into three phases: mitosis, meiosis andspermiogenesis. To generate mature spermatozoa, the SSCs complete self-renewaland proliferation by mitosis, and differentiate from spermatogonia to secondaryspermatocytes through meiosis, the haploid spermatids undergo a series of complexprocess and ultimately form mature sperm. Spermiogenesis was a unique processinvolved in formation of acrosome and sperm tail, elongation and condensation ofnucleus, and removal of unnecessary cytoplasm. The acrosome was a uniquemembranous apparatus that was formed during spermiogenesis through an integratedprocess of transport vesicle production, trafficking and fusion. Golgi apparatus is avery important organelle during acrosome formation. At present, four Golgi proteinshave been reported in pachytene spermatocytes, round and elongating spermatids:giantin, β-COP, Golgin-97and Golgin-95/GM130.In the early stage of the study, we established a series of proteome profiles ofspermatogenesis and provided several important protein lists to understand theregulation of male fertility and infertility. Here, we chose Flotillin-2for further study.To better understand the function of Flotillin-2, we have done a lot of research. Ourresults showed Flotillin-2was highly expressed in male germ cells, and it expressedin pachytene spermatocyte as a strong dot signal and then as sickle distribution aheadof the acrosome in round spermatid during spermiogenesis. To clearly clarify therelation between acrosome and localization of Flotillin-2, we used PNA to label theouter acrosomal membrane and indirect immunofluorescence of Flotillin-2at thesame time. Immunofluorescence further showed Flotillin-2was localized in front of acrosome in round spermatid and this location indicated it might be Golgi apparatus.Further, we studied function of Flotillin-2by means of microinjection combined withRNAi. The decreased expression of Flotillin-2through injection of SiRNA againstFlotillin-2into mouse testis caused significant increased head abnormalities in spermfrom cauda epididymis compared with the negative control. Flotillin-2may beimportant for formation of acrosome.In summary, we proposed that Flotillin-2is important for spermiogenesis. It maybe a novel Golgi-related protein in sperm acrosome biogenesis. So exploring thefunction of Flotillin-2provides us a powerful clue to study male sterility.