Studies on the Regulation of Fertilization and Activation of Development

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To elucidate the regulation of fertilization and activation of development, we have examined possible functions of mouse sperm in sperm maturation, sperm transit from uterus to oviduct, fertilization, and egg activation. The following experimental results have been obtained :1. The TritonX-100-insoluble microdomains, lipid rafts, on the plasma membranes of epididymal sperm gradually move to the apical region from the equatorial region of sperm during capacitation.2. Male mice lacking sperm PH-20 are still fertile, in spite of a reduced ability to disperse cuwnulus cells from the cumulus mass. Western blot analysis of sperm extracts reveals the presence of other hyaluronidase(s), except PH-20, presumably within the sperm acrosome. These data provide evidence that PH-20 is not essential for fertilization at least in the mouse, and suggest that the other hyaluronidase(s) may play an important role in the sperm penetration through the cumulus cell layer and/or the egg zona pellucida, possi … More bly in cooperation with PH-20.3. Mouse genomic clones encoding a 42-kDa sperm serine protease, TESP5, have been identified. Immunochemical analysis reveals that 42- and 4l-kDa forms of TESP5 are localized in the head, cytoplasmic droplet, and tail of cauda epididymal sperm probably as a glycosylphosphatidylinositol-anchored membranous protein. Moreover, these two forms of TESP5 are selectively included into Triton X-100-insoluble microdomains, Iipid rafts, of the sperm membranes. These results suggest a possible involvement of TESP5 in the sperm/egg interactions.4. Two different ADAMI isoforms, ADAMla and ADAMlb, instead of ADAMl are present in the mouse testis. ADAMla is resttrictedly present within the endoplasmic reticulum of germ cells, whereas epididymal sperm contain only ADAMlb on the cell surface. The precursors of ADAMla and ADAMlb form a heterodimeric complex with that of ADAM2 in the endoplasmic reticulum of germ cells. The heterodimeric complex between the mature forms of ADAMlb and ADAM2 is also found on the sperm surface. These data imply the potential roles of ADAMla and ADAMlb in spermatogenesis and fertilization, respectively.5. When a synthesized mRNA with a poly(A) tail encoding phospholipase ζ is injected into unfertilized eggs, pronuclear formation is observed. Less