ANALYSIS OF MOUSE OOCYTE ACTIVATION SUGGESTS THE INVOLVEMENT OF SPERMPERINUCLEAR MATERIAL

The mouse oocyte can be activated by injection of a single, intact mou se spermatozoon or its isolated head. Isolated tails are unable to act ivate the oocyte. Active sperm-borne oocyte-activating factor(s) (SOAF ) appears during transformation of the round spermatid into the sperma tozoon. The action of SOAF is not highly species-specific: mouse oocyt es are activated by injection of spermatozoa from foreign species, suc h as the hamster, rabbit, pig, human, and even fish. Some SOAF can be extracted by simple freeze-thawing of (hamster) spermatozoa; additiona l SOAF is obtained by sequential treatment of spermatozoa with Triton X-100 and SDS. Electron microscopic examination of sperm heads during SOAF extraction suggests that the relatively insoluble SOAF is associa ted with perinuclear material. When microsurgically injected into oocy tes, Triton X-100-treated sperm heads (with perinuclear material, but without any membranes) can activate the oocytes, leading to normal emb ryonic development. Whereas perinuclear components have been believed to play a purely structural role, these data suggest an additional fun ction for them in oocyte activation.