Sperm-egg

The acrosome reaction is the loss of the acrosomal and plasma membranes in the acrosome region and the release of acrosin, hyaluronidase and other enzymes that disperse the cumulus complex and allow the sperm to penetrate the zona pellucida. After capacitation and the acrosome reaction, sperm penetrate the extracellular cumulus matrix and bind with zona protein 3, a heavily glycosylated protein of the zona pellucida. The first segment of the sperm to make contact with the oolemma is usually the inner acrosomal membrane, followed by the postacrosomal region. The plasma membrane of the sperm attaches to microvilli on the oolemma. Sperm-egg fusion is apparent from reduced movement of the sperm tail (Yanagimachi, 1970,1988 Takano et al.,... 

Yanagimachi R (1988) Sperm-egg fusion. Cun Topics Membrane Transport, 32 349-363. 

Focarelli, R., La Sala, G. B., Balasini, M., and Rosati, F. (2001) Carbohydrate-mediated sperm-egg interaction and species specificity a clue from the Unio elon-gatulus model. Cells Tissues Organs 168(1-2), 76-81. 

Metz, E.C., Kane, R.E., Tanagimachi, H., and Palumbi, S.R., Fertilization between closely related sea urchins is blocked by incompatibihties during sperm-egg attachment and early stages of fusion, Biol. Bull., 187, 23, 1994. 

There is considerable evidence that calcium acts as a primary trigger for egg maturation and fertilization in several phyla. Calcium regulation has been demonstrated or suggested for numerous specific events in fertilization, including sperm motility, the acrosome reaction, sperm-egg binding and fusion and metabolic activation of egg, etc. However, very little is known concerning the mechanisms whereby calcium exerts its effects. 

Rubinstein, E., Ziyyat, A., Wolf, J.R, Le Naour, F. and Boucheix, C. (2006) The molecular players of sperm-egg fusion in mammals. Semin. Cell Dev. Biol. 17,254—263. 

Yanagimachi, R. Sperm-egg fusion. In Current Topics in Membranes and Transport Academic Press NY, 1988 32, 3 3. 

The second class of proteins that seem to bind mannose 6-phosphate and sulfated oligosaccharides derived from heparin are the seminal plasma spermadhesins, a group of small, structurally well defined proteins with possible biological function in sperm capacitation and sperm-egg interaction [236,237]. 

The steps in abalone sperm-egg interaction were deduced from light and electron microscopic studies (Figure 4). First, the sperm plasma membrane covering the tip... 

Figure 4. Scheme showing sperm-egg interaction in the abalone. 1. The sperm binds to the egg VE by the plasma membrane at the tip of the AV (AG), (F, flagellum M, mitochondrion N, nucleus). 2. The sperm acrosome reacts releasing lysin and the 18K protein from its anterior tip. 3. Lysin disrupts the fibers of the VE and the 18K coats the extending acrosome process as it extends. 4. The sperm passes through the hole in the VE and the membrane covering the tip of the acrosomal process fuses with the egg (from Vacquier and Lee, 1993). 

To summarize, variable structural features of lysins suggest ways to attack the elucidation of the molecular mechanism of species-specific sperm-egg recognition in abalones. The invariant structural features of lysins suggest ways to explore the molecular mechanism lysin uses to destroy nonenzymatically the integrity of the VE to allow the sperm to pass through this protective envelope and contact the egg cell membrane. 

O Rand, M.G. (1988). Sperm-egg recognition and barriers to interspecies fertilization. Gamete Res. 79 315-328. 

Yanagimachi, R. (1988b). Sperm-egg fusion. Curr. Top. Membr. Transport, 52 3-43. 

Bigler, D., Chen, M., Waters, S., and White, J.M. (1997). A model for sperm-egg binding and fusion based on ADAMs and integrins. TIBS. 7 220-225. 

Blobel, C.P., Myles, D.G., Primakoff, P., and White, J.W. (1990). Proteolytic processing of a protein involved in sperm-egg fusion correlates with acquisition of fertilization competence. J.Cell iol. 777 69-78. 

Evans, J.P., Schultz, R.M., and Kopf, G.S. (1995). Mouse sperm-egg plasma membrane interactions Analysis of roles of egg integrins and the mouse homologue of PH-30 (fertilin) p. J. Cell Sci. 705 3267-3278. 

Heinlein, U. A.O., Wallat, S., Senftleben, A., and Lemaire, L. (1994). Male germ cell-expressed mouse gene T AZ83 encodes a putative, cysteine rich transmembrane protein (cyritestin) sharing homologies with snake venom toxins and sperm egg fusion proteins. Dev. Growth and Diff. 36 49-58. 

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