Implication of Amphiphysin 1 and Dynamin 2 in Tubulobulbar Complex Formation and Spermatid Release

抄録

Tubulobulbar complexes (TBC) are composed of several tubular invaginations formed at the plasma membrane of testicular Sertoli cells. TBC is transiently formed at contact region with spermatids at spermatogenic stage VII in rat and mouse, and the TBC formation is prerequisite for spermatid release. Since the characteristic structure of TBC suggests that the molecules implicated in endocytosis could be involved in TBC formation, we here investigated the localization and physiological roles of endocytic proteins, amphiphysin 1 and dynamin 2, at TBC. We demonstrated by immunofluorescence that the endocytic proteins were concentrated at TBC, where they colocalized with cytoskeletal proteins, such as actin and vinculin. Immunoelectron microscopy disclosed that both amphiphysin 1 and dynamin 2 were localized on the membrane of TBC. Next, we histologically examined the testis from amphiphysin 1 deficient {Amph^-/-} mice. Morphometric analysis revealed that the number of TBCs was significantly reduced in Amph^-/-. The ratio of stage VIII seminiferous tubules was increased, and the ratio of stage IX was contrarily decreased in Amph^-/-. Moreover, unreleased spermatids in stage VIII seminiferous tubules were increased in Amph^-/-, indicating that spermatid release and the following transition from stage VIII to IX was prolonged in Amph^-/- mice. These results suggest that amphiphysin 1 and dynamin 2 are involved in TBC formation and spermatid release at Sertoli cells.