MOUSE embryos have been made by fertilising eggs with immature sperm cells derived from embryonic stem cells. “But we will be quite surprised if the embryos develop normally,” warns George Daley of Harvard Medical School.
Earlier this year, a group in Japan showed that mouse embryonic stem cells (ESCs) could be turned into sperm-like cells, while a group in the US turned them into egg-like cells (Â鶹´«Ã½, 10 May, p 4). This work might one day make it possible for infertile couples to have children, using sperm or eggs derived by therapeutic cloning. But until now, no team…
