Stem cells bear eggs

摘要

Unlike testes, ovaries do not make gametes throughout life: female mammals are born with a limited supply of oocytes (eggs), which progressively decrease in number until the menopause. This biological barrier has complicated the study both of oocyte development in mammals and of the mechanisms underlying female infertility. Reporting in the latest issue of Science, Hayashi et a~1 have induced embryonic stem cells to develop into mature oocytes that, when fertilized, give rise to apparently normal, fertile animals.