THE ROLE OF CALCIUM IN MAMMALIAN OOCYTE MATURATION AND EGG ACTIVATION

The maturation of the immature oocyte and the fertilization of a matur e egg are two absolute prerequisites for mammalian embryo development. There is increasing evidence in mammals that both oocyte maturation a nd egg activation at fertilization are controlled by changes in intrac ellular free Ca2+ levels. The role of Ca2+ changes at fertilization is clear in that they are both required and sufficient for egg activatio n. However, it is not established how the sperm causes Ca2+ changes in eggs at fertilization, nor how different patterns of Ca2+ change affe ct embryo development. The role of Ca2+ in triggering oocyte maturatio n is less clear, although preventing intracellular Ca2+ changes can in hibit meiotic maturation at specific stages. Studies on how Ca2+ regul ates meiosis and fertilization in mammals may provide new insights int o the causes of failed fertilization in human IVF procedures.