is a Japanese reproductive geneticist and stem cell researcher. He achieved same-sex reproduction of male mice and thus ranked Nature's 10. He has been studying the mechanism by which germ cells that transmit genetic information to the next generation are produced. In particular, he has identified the molecules and environmental factors that control the differentiation process of the oocyte lineage leading to eggs by reconstructing this process using pluripotent stem cells. Recently, based on these studies, he has been conducting research into the quality control mechanism of genetic information in the oocyte lineage and the diseases caused by its breakdown.