The critical aim of all assisted reproductive technologies is to achieve the fertilization of an oocyte with a sperm. When a patient’s sperm count is too low, and lacks good sperm motility, it becomes necessary to perform ICSI. Although ICSI can improve fertilization rates, pregnancy rates after performing ICSI are known to be lower than pregnancy rates following the performance of IVF. Moreover, we have recently found that meiotic failure at the time of the second polar body extrusion is higher in cases of ICSI than in cases of IVF. It is well known that the rate of chromosomal abnormalities in fertilized oocytes is very high, especially when the women's age is over 42, at which point the chromosomal abnormalities in their fertilized oocytes exceeds 80%. As neither the process of culturing human embryos nor ICSI technology have been perfected at this stage, we aim to develop novel technologies, based on basic experiments employing mouse models.

　In human oocytes, we occasionally encounter patients whose oocyte spindles cannot be detected under a polarization microscope, although this is rare. Despite the performance of IVF, ICSI and even oocyte activation, these oocytes do not achieve in normal fertilization. The reasons and mechanisms behind this failure are still unknown. We aim to perform functional analyses of the process of oogenesis, during the first and second meiosis using oocytes from mutant mice, which present with a mutation, leading to genetically developed abnormalities on chromosomal crossing-over during meiosis. In this way, we hope to contribute to the existing body of therapeutic strategies and preventive measures which can be taken against human infertility. * This study is a collaborative work with the unit of Applied Animal Genetics at Okayama University.

　The dysmorphic phenotypes to be found in human oocytes are unlike any other species, with the exception of chimpanzee oocytes. Among these dysmorphisms, we have been focusing on two phenotypes: smooth endoplasmic reticulum clusters (sERCs) and refractile/lipofuscin bodies. We have found that the incidence of mitotic and meiotic cleavage failure during the second polar body extrusion is significantly higher in oocytes with sERCs than that in oocytes without sERCs. Regarding the refractile body, we have reported that it presents with autofluorescence. Viewed by means of transmitted electron microscopy, the refractile bodies display the conventional morphology of lipofuscin inclusions and consist of a mixture of lipids and dense granule materials. We aim to elucidate the mechanisms of these dysmorphic phenotypes in human oocytes and work towards preventive measures against them. * This study is a collaborative work with the Okayama University Hospital and Fertility clinics.