Importance of the interactions between intracellular signalling pathways during sperm acquisition of 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. Although structurally complete at the exit of the testis, they must reside in the female reproductive tract where they undergo surface and intracellular modifications, named as a whole as capacitation, to become fully fertilization competent. 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. Although the requirement for Ca2+ for these events is known for many years, the mechanisms that control its intracellular levels and its exact roles during sperm capacitation remain to be elucidated. In this research proposal, we will investigate the biochemical events that are involved in the storage of intracellular Ca2+, which will be necessary later when the spermatozoa will interact with the egg. Another objective is to investigate further the importance of Ca2+ in sperm capacitation, such as the dynamics of actin polymerization and depolymerization, and to determine whether it involves or is affected by protein tyrosine phosphorylation. The changes in sperm intracellular biochemical reactions elucidated in this research program will undoubtedly lead to a better knowledge on sperm fertilizing ability and sperm/egg interactions, which would ultimately help to detect and have impact on fertility problems encountered in endangered animal species where the quality of semen and of spermatozoa are often defective. Impact could also be applicable to humans as well since lifestyle and environment have strong impacts on sperm fertilizing ability and, therefore, male fertility. Highly importantly, my research program is directly related to agricultural industries like dairy or meat, which depend on successful reproduction. This is further emphasized by the importance of artificial insemination in livestock reproduction, more specifically when cryopreserved semen is used. Although this process gives numerous advantages, it affects sperm viability and fertilizing ability, which explains why more spermatozoa are required per insemination units when compared with fresh non-frozen semen. Therefore, results obtained through this research proposal can ultimately results in changes in the cryopreservation process that will ultimately reduce the number of spermatozoa per insemination unit without affecting fertilization rate.