Intracellular signalling events leading to sperm fertilization 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 this 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 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 from the uterus and oviduct, and become fully fertilization competent in a process called capacitation. This phenomenon is associated with the hyperactivation of sperm motility, which is more vigorous, with increased velocity and strength to facilitate sperm passage through egg associated 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 prior to ovulation. The mechanisms regulating the processes of capacitation and sperm/egg interactions are not fully understood, although modification in different intracellular signal transduction pathways affecting cyclic AMP levels, Ca2+ concentration, pH, protein tyrosine phosphorylation, and actin reorganization are known to occur. My research program is devoted to further investigate sperm intracellular events during the acquisition of sperm fertilizing ability and to better characterize how spermatozoa become competent to successfully interact with the egg, fertilize it, and initiate the 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.