Cytoskeletal assemblies of mammalian spermatozoa.

It is becoming increasingly evident that the different domains of the mammalian spermatozoa possess distinct cytoskeletal assemblies. In this paper we have discussed three assemblies, found in the acrosomal, postacrosomal, and midpiece segment, respectively. Each has a distinct substructure and associates with specific sperm-membrane systems. Their protein compositions are currently unidentified, and they may be comprised of sperm-specific polypeptides. Analysis of their formation and fate during sperm-egg interaction should provide valuable insight into their role in the development of cell polarity and in the membrane-mediated steps of fertilization.