Cytoskeletal aspects of assisted fertilization

During mammalian fertilization, the zygotic centrosome organizes a large sp erm aster; critical for uniting the male and female pronuclei prior to firs t mitosis. Fluorescent imaging of inseminated human oocytes has shown that centrosomal defects may result in abnormal microtubule nucleation preventin g genomic union, suggesting a novel cause of fertilization failure. Working with rhesus monkey gametes, we have developed a preclinical model for unde rstanding the cell biological basis of intracytoplasmic sperm injection (IC SI). Typically ICSI results in abnormal nuclear remodeling during sperm dec ondensation due to the presence of the sperm acrosome and perinuclear theca , structures normally removed at the oolemma during IVF; this is turn cause s a delay in the onset of DNA synthesis. These unusual modifications raise concerns that the ICSI procedure itself may result in chromatin damage duri ng DNA decondensation and further highlight the need for a move rigorous as sessment of methods of assisted reproduction prior to their global applicat ion.