Involvement of Complexin 2 in Docking, Locking and Unlocking of Different SNARE Complexes during Sperm Capacitation and Induced Acrosomal Exocytosis
Figure 1
Ultrastructural morphology of acrosome reacted spermatozoa and the subsequently formed MVs.
(A) MVs were present around the apical sperm head after AE was induced by calcium ionophore in the absence of bicarbonate. (B) The same was observed for sperm that were first capacitated in presence of bicarbonate and then challenged with Ca2+ ionophore. (C) MVs isolated from sperm treated as in panel A appeared as unilamellar membrane vesicle structures with a relatively large variation in size (126.7±54.5 nm) and in shape. (D) Unilamellar membrane vesicles isolated from sperm treated as in panel B showed a more homogeneous shape and size (184.4±28.5 nM). These MVs also appear to have more acrosomal matrix components associated to one side of the vesicles (arrow heads) as was already manifest before the MV shedding of the sperm head (see panel B). Statistical analyses on the morphology of MVs present in (C) and (D) were carried out by evaluating three sections from three independent samples (n = 3 values are indicated ± SD). Bar represents 200 nm.