Sperm membrane incorporation into oolemma contributes to the oolemma block to sperm penetration: Evidence based on intracytoplasmic sperm injection experiments in the mouse

Perfect date—the review of current research into molecular bases of mammalian fertilization

“…Interestingly, when gamete recognition was circumvented by ICSI, Juno was not removed from the oocyte surface and the egg remained receptive to further sperm [78]. This finding is consistent with previous observations that ICSI does not induce an effective block to polyspermy in mammalian eggs [118,119]. Studies are being undertaken to provide the evidence that the removal of Juno from egg s surface contributes to the establishment of a polyspermy block in humans.…”

Decrease in CD9 content and reorganization of microvilli may contribute to the oolemma block to sperm penetration during fertilization of mouse oocyte

“…Modification of the structure of the oolemma, as well as the changes in localization of CD9, which we observed after fertilization, likewise the oolemma block to sperm penetration (Komar, 1982;Borsuk & Tarkowski, 1989;Horvath et al, 1993;Maleszewski & Bielak, 1993;Maleszewski et al, 1996;Pyrzynska et al, 1996;Wortzman-Show et al, 2007), must be only partially related to the oocyte activation, as these phenomena do not occur in parthenogenetically activated oocytes. The changes in the structure of oolemma and, in consequence, the membrane block to sperm penetration Gardner & Evans, 2006), can be induced by the fusion of the membranes of the gametes.…”

Prophase I Mouse Oocytes Are Deficient in the Ability to Respond to Fertilization by Decreasing Membrane Receptivity to Sperm and Establishing a Membrane Block to Polyspermy1

“…As addressed in the Introduction, increased [Ca 2þ ] cyt facilitates membrane block establishment but is not sufficient [51,54], making membrane block establishment different from most other egg activation events, nearly all of which are entirely Ca 2þ dependent [99]. Although one model for membrane block establishment was that sperm-egg fusion and incorporation of the sperm membrane into the egg membrane is the trigger [55], the work here provides clear evidence that sperm-egg fusion is not sufficient to trigger normal membrane block establishment because sperm obviously fuse with prophase I oocytes and yet the membrane block response is significantly deficient. This indicates that the membrane block to polyspermy is a two-part process: the sperm provides the trigger, and the female gamete must be capable of responding to the fertilizing sperm.…”