Post-ICSI cytoskeletal dynamics during fertilization

Although intracytoplasmic sperm injection (ICSI) is an innovative treatment for male infertility, a significant number of clinical cases of fertilization failure remain. ICSI overcomes the difficulty in fertilization of sperm entry into the egg cytoplasm. The goal of fertilization, however, is the union of the male and female genomes; sperm incorporation into the oocyte is only the start of fertilization. Human sperm must perform three vital functions after entering the egg: it contributes to the male genome, awakens the quiescent egg, and crystallizes the motility apparatus that unites the sperm and egg nuclei, consummating the fertilization process. During fertilization in most mammalian species, including humans, the sperm introduces the centrosome, which acts as a microtubule organizing center (MTOC). By promoting pronuclear apposition and mitotic spindle formation, the sperm plays the leading part in the induction of “motility”, post-ICSI, in fertilization. The present review introduces the challenges remaining in functional assessment of the human sperm centrosome and discusses the biparental (e.g. rabbit) and maternal (e.g. parthenogenesis) centrosomal contributions to microtubule organization during development.