Isolation and Maintenance of Primate Embryonic Stem Cells

Primate embryonic stem (ES) cells are derived from preimplantation embryos and are capable of prolonged undifferentiated proliferation in culture. Under particular conditions, these cells differentiate into derivatives of endoderm, mesoderm, ectoderm, and trophoblast (1 ,2 ). In mammals, many developmental events are studied using mouse embryos or ES cells, but some aspects of development differ significantly between humans and mice, such as the timing of embryonic genome expression (3 ), fetal membrane and placental structure and development (4 –6 ), and the formation of an embryonic disc instead of an egg cylinder (7 ,8 ). These and other features of human development are better studied using a primate model.