Balls of Cells Mimic Unseen Stage of Human Embryo Development

June 12, 2020

(Science) – After a human sperm and egg unite, a new embryo spends its first few weeks looking blobby. There’s no obvious top or bottom, and it is unclear which cells will give rise to which body parts. After about 14 days, the embryo elongates and forms layers, revealing a rough plan for the body. But this dramatic transformation, called gastrulation, has never been directly observed in human embryos: Growing them to this stage in a lab is technically difficult and ethically fraught. Now, researchers have made structures from human stem cells that mimic some features of embryos after gastrulation, an advance that could reveal how genetic mutations and chemical exposures can lead to miscarriages and birth defects.