The Employment of Apoptosis in Embryonic Development

Programmed cell death is necessary for the elimination of excess or damaged cells in all stages of life, but this is especially true during embryonic and fetal development of mammals. Beginning before implantation and continuing until birth, both intrinsic and extrinsic apoptosis are employed within mammalian embryos to ensure the viability of the organism, proper organ morphogenesis, integrity of the genetic material, and the high quality of the germ line. The formation of both transient and permanent ectodermal, mesodermal, and endodermal structures often involves apoptosis. In this review, a selection of apoptotic events within each germ layer and occurrences of apoptotic dysregulation will be discussed. The study of apoptosis in mammalian development demonstrates the meticulous genetic control necessary for life.