O-285 Incompatible gametes: implications for infertility diagnosis and treatment

Sperm face intense selection in the female reproductive tract (FRT), and in humans usually only very few out of up to hundreds of millions of sperm cells can eventually proceed to the vicinity of an unfertilized oocyte. Traditionally, it has been thought that the primary function of female-induced sperm selection is to eliminate poor-quality sperm from reaching the oocyte. However, recent studies have demonstrated that in many species (including humans) FRT also mediate mate choice at the level of the gametes, which frequently bias fertilization towards the male, which is genetically compatible with the female. Furthermore, emerging evidence indicates that sperm phenotypic and genotypic variation within single ejaculates may allow gamete-level mate choice to act also among high-quality (‘healthy’) sperm and bias fertilization towards genetically compatible sperm haplotypes. I argue that both of these cellular-level mate choice processes can have important consequences for deeper understanding of the mechanistic basis of fertilization and infertility.