Adhesion molecules in human sperm-oocyte interaction: relevance to infertility

Fertilization involves cell-cell fusion of a sperm with the oocyte. This fusion restores the diploid genome, activates the oocyte, and initiates embryonic development. The identification of proteins mediating the fusion of sperm with oocyte plasma membrane (oolemma) is important to a deeper knowledge of fertilization. Defects in sperm-oocyte fusion may account for some form of human infertility. The hypothesis that sperm plasma membrane and oolemma carry complementary molecules involved in multistep fusion process has been validated by studies of cell adhesion molecules (integrins) in sperm-oocyte interaction in a number of animal models and human in vitro fertilization assays. Integrins or integrin-like molecules and complement proteins present on the surface of mammalian gametes, might be involved in the interaction between oocyte and sperm at fertilization. This review will provide an overview of the interaction of human sperm membrane with the oolemma, the nature of cell adhesion molecules, their expression profiles and their possible involvement in adhesive and fusogenic events in human fertilization. Unraveling the unique molecules involved in human sperm plasma membrane-oolemma fusion will be an important component for the development of a new set of contraceptive vaccines.