Exploring sperm function

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At ejaculation, sperm cannot fertilise. They must first undergo capacitation, which is broadly defined as the modifications that render sperm competent to fertilise. A hallmark of capacitation is the ability of the sperm to undergo the acrosome reaction, a calcium-dependent, secretory event, in response to the egg's extracellular matrix, the zona pellucida. Just how the sperm, a highly compartmentalised and non-transcriptional cell, undergoes the complexities of capacitation and the acrosome reaction remains unclear. Using the porcine model, we previously showed that capacitation is associated with the appearance of "p32", a tyrosine phosphoprotein. Early proteomics revealed that p32 is actually a complex of >9 tyrosine phosphoproteins and that the principle tyrosine phosphoprotein appearing during capacitation to be Sp32. This protein was first known as an acrosomal protein involved in acrosin maturation, however, Sp32 itself has zona-binding affinity and has been identified as a cancer-testis antigen. Our long term objective is to establish an integrated model of sperm function at the gene and protein level including capacitation and the acrosome reaction in a context of comparative biology. Our short term objectives are to identify, localise and characterise p32 complex components, to characterise Sp32 and to identify the pathways mediating capacitation and the acrosome reaction. This program will clarify how post-translational protein modifications lead to sperm competence and how capacitation and the acrosome reaction are regulated. Such use-inspired basic research is instrumental to resolve causes of infertility, formulate rational contraception, improve assisted reproductive techniques, and interpret toxicological effects on male reproduction. Fertility control is necessary in human and veterinary medicine, animal agriculture, pest control, and to conserve endangered species.