The role of dynamin 3 in the testis.

We report here that dynamin 3 in the testis is associated with structures termed tubulobulbar complexes that internalize intact intercellular junctions during sperm release and turnover of the blood-testis barrier. The protein lies adjacent to an actin-Arp2/3 network that cuffs the double plasma membrane tubular invagination at the core of each complex. To explore the possible relationship between dynamin 3 and nectin-based adhesion junctions, we transiently transfected DsRed-tagged dynamin 3 into MDCK cells stably transfected with eGFP-tagged nectin 2, one of the adhesion molecules known to be expressed in Sertoli cells at adhesion junctions. Cells transfected with the dynamin 3 construct had less uniformly distributed nectin 2 at intercellular contacts when compared to control cells expressing only nectin 2 or transfected with the DsRed plasmid alone. Significantly, tubular extensions positive for nectin 2 were visible projecting into the cells from regions of intercellular contact. Our findings are consistent with the conclusion that dynamin 3 is involved with tubulobulbar morphogenesis. Dynamin 3 also occurs in concentrated deposits around the capitulum and striated columns in the connecting piece of sperm tails suggesting that the protein in these cells may function to stabilize the base of the tail or serve as a reservoir for use during or after fertilization. Copyright 2006 Wiley-Liss, Inc.