Placental development: Lessons from mouse mutants

The placenta is the first organ to form during mammalian embryogenesis. Pro blems in its formation and function underlie many aspects of early pregnanc y loss and pregnancy complications in humans. Because the placenta is criti cal for survival, it is very sensitive to genetic disruption, as reflected by the ever-increasing list of targeted mouse mutations that cause placenta l defects. Recent studies of mouse mutants with disrupted placental develop ment indicate that signalling interactions between the placental trophoblas t and embryonic cells have a key role in placental morphogenesis. Furtherin g our understanding of mouse trophoblast development should provide novel i nsights into human placental function.