Incorporation and dispersal of sperm surface antigens in plasma membranes of inseminated sea urchin (Arbacia punctulata) eggs and oocytes.

Monoclonal antibodies have been generated to determine the fate of sperm-specific surface components of the sea urchin, Arbacia punctulata, subsequent to gamete fusion. Monoclonal antibody-7 (MAB-7) reacted with two polypeptide bands having apparent molecular masses of 33 and 35 kDa derived from the sperm plasma membrane; similar reactivity was not detected in egg preparations. Eggs and oocytes were prepared for electron microscopy at periodic intervals following insemination and reacted with MAB-7 followed by antimouse antibodies conjugated to colloidal gold. In samples prepared 30 to 60 sec postinsemination (PI) colloidal gold was confined to the surface of fused sperm with only a few gold particles associated with the egg plasma membrane. In later samples (2-10 min PI) label was present on increasingly greater areas of the egg/oocyte surface away from the site of gamete fusion so that by 20 min PI particles were located along one hemisphere of inseminated eggs and oocytes. These results demonstrate the incorporation of sperm plasma membrane polypeptides and their intermixing with egg plasmalemmal components subsequent to gamete membrane fusion. From measurements of labeled oocytes at different times PI, the diffusion coefficient for sperm surface polypeptides detected by MAB-7 was estimated to be 0.7 to 2.4 x 10(-9) cm2/sec.