Mammalian oocyte activation by the synergistic action of discrete sperm head components: Induction of calcium transients and involvement of proteolysis
Perry, A. C. F., Wakayama, T., Cooke, I. M. and Yanagimachi, R., 2000. Mammalian oocyte activation by the synergistic action of discrete sperm head components: Induction of calcium transients and involvement of proteolysis. Developmental Biology, 217 (2), pp. 386-393.
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Sperm-borne oocyte-activating factor (SOAF) elicits activation sufficient for full development and originates from sperm head submembrane matrices. SOAF comprises discrete, heat-sensitive and -stable components (referred to here respectively as SOAF-I and -II) which are each necessary but not sufficient to activate oocytes. The heat-sensitive SOAF component, SOAF-I-m, becomes solubilized from the perinuclear matrix under reducing conditions (the SOAF transition) to generate SOAF-I-s. Although calcium transients likely play an important role in oocyte activation at fertilization, the question is open as to whether demembranated heads or SOAF-I-s and/or SOAF-II can induce calcium transients. We now report that injection of demembranated sperm heads into mouse oocytes efficiently induced Ca2+ oscillations. When injected independently, SOAF-I-s and demembranated heads heated to 48 degrees C failed to generate Ca2+ oscillations. However, co-injection of SOAF-I-s and 48 degrees C-heated heads induced oscillations, mirroring their synergistic ability to activate oocytes. This suggests that SOAF-mediated activation proceeds via pathways resembling those at fertilization and provides the first direct evidence that multiple sperm components are required to induce Ca2+ oscillations. We probed the SOAF-I-s liberation at the center of this activation and show that in vitro it was sensitive to a profile of serine protease inhibitors. These findings support a model in which mammalian oocyte activation, including the induction of calcium transients, involves proteolytic processing of SOAF from sperm head submembrane compartments.
|Creators||Perry, A. C. F., Wakayama, T., Cooke, I. M. and Yanagimachi, R.|
|Departments||Faculty of Science > Biology & Biochemistry|
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