Importance of intracellular signaling in the regulation of sperm fertilizing competence

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Spermatozoa are highly differentiated cells which only role is to fertilize the egg in order to produce a new individual. To achieve its goal, spermatozoa are made of two distinct compartments linked together: the head which contains half of the paternal genetic content, and the flagellum, which is the mobility organ required to bring the genetic content in contact with the egg. Although structurally complete at the exit of the testis, sperm cells acquire the ability to move and to interact with the ovulated egg during the epididymal transit. However, they but remain in immotile until ejaculation, when they are mixed with the secretions from the seminal vesicles and the prostate. This process is called motility activation. Once in the female reproductive tract, sperm interacts with cells and secretion, and become fully fertilization competent in a process called capacitation and is associated with the hyperactivation of sperm motility, which is more vigorous, increasing cell velocity and strength to facilitate sperm passage through egg associated vestments such as the cumulus, a highly viscous proteoglycan-rich fluid containing cumulus cells linked together, and the zona pellucida, a relatively thick extracellular matrix produced by the growing oocyte. The mechanisms regulating the processes of capacitation and sperm/egg interactions are not fully understood although agents affecting different intracellular signal transduction pathways regulating cyclic AMP-, Ca2+-, pH-, and protein tyrosine phosphorylation-mediated events are involved. My research program is devoted to further investigate sperm intracellular biochemical events during the acquisition of sperm fertilizing ability and to better characterize the mediators involved in the sperm interactions with the egg that will result in fertilization and early development of a genetically unique individual. This research program will undoubtedly have impact on fertility problems encountered in endangered species, in agricultural industries (dairy, meat) that depend on successful reproduction and, ultimately in humans where lifestyle and environment have strong impacts on male fertility.