Study on the mechanism of maternal imprinting during oocyte growth.

In mammals, both parental genomes are essential for normal ontogeny because epigenetic modifications imposed in the parents' gametes lead to parent-of-origin specific gene expression in their offspring. These phenomena are referred to as genomic imprinting. It has been shown that maternal imprinting is established during oocyte growth, lack of maternal imprinting in zygotes leads to early embryonic death, and in vitro system that allows establishment of maternal imprinting is developed. In this review, I describe the history of the discovery of genomic imprinting, the regulatory mechanisms of mammalian development by maternal imprinting, and the molecular mechanisms of genomic imprinting.