CONICET | Buscador de Institutos y Recursos Humanos

Our group is interested in the study of signaling events that are involved in sperm differentiation and function. A family of serine/threonine kinases (Testis specific serine kinases (Tssk)) has been found postmeiotically expressed in the male germ cells. Previously, our group showed that male, but not female, mice lacking Tssk6 (aka Sstk), one of the Tssk family members, were sterile. Although the direct substrate of this serine/threonine kinase remains unknown, the sperm produced by these mice presents defects that prevent the successful fertilization of eggs in vitro. With further analysis we found that these sperm were able to attach to zona-free eggs but were incapable of undergoing membrane fusion. One of the most important, yet mechanistically unknown processes in fertilization is the fusion of the sperm and the egg. Thus far, only two proteins have been demonstrated using knock out approaches to be necessary for this process: CD9 in the egg and Izumo in the sperm. In this work, we analyzed the behavior of Izumo in sperm from Tssk6-/- mice. In WT sperm, immunofluorescent staining indicates that Izumo localizes to the anterior head, however, after the acrosome reaction, the signal relocates to other regions of the head including the postacrosomal compartment. In contrast, in Tssk6 null sperm, Izumo does not change its immunolocalization after the acrosome reaction. Additional evidence suggests that changes in Izumo immunofluorescent pattern involve actin polymerization. , phalloidin failed to detect polymerized actin in the head of Tssk6 -/- sperm. Altogether, these data suggest that Tssk6 is related in redistribution of Izumo after the acrosome reaction and that this re-localization is necessary for sperm-egg fusion.