The invention provides a microinsertion-based, trans-complementation method of in vitro oocyte activation useful to identify properties of sperm-borne oocyte-activating factor(s) (SOAF) and ooplasmic interactions with sperm components at fertilization. The invention provides at least one detergent-insoluble heat-sensitive component of the perinuclear matrix of a spermatozoon (SOAFm) that acts coordinately with at least one heat-stable submembrane sperm component. SOAFm is solubilized in vitro (SOAFs) under reducing conditions similar to those encountered in the ooplasm. By the method of the invention, the failure of heat-inactivated demembranated sperm heads to activate an egg is rescued by coinsertion of SOAFs into an oocyte. SOAFs is protease-sensitive and is liberated from demembranated heads in a temperature-dependent manner that inversely correlates with the ability of demembranated sperm heads to activate oocytes.
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