Primate amnion development

Formation of the amnion in humans is crucial for fetal development and a healthy pregnancy. In addition to providing a protective layer to the developing fetus as a component of the amniochorionic fetal membranes, the amnion serves as a signaling center for patterning early embryonic tissues. However, because the amnion is first specified in the human epiblast during implantation, the molecular and cellular events of this early amniogenic process in humans cannot be studied in utero. Recent developments using new human stem cell-derived model systems, as well as single-cell and spatial transcriptomic analyses of early human and monkey embryos, have uncovered new insights into the underpinnings of primate amnion specification. Here, we highlight recent findings from human and monkey models with an emphasis on current understandings of morphogenesis, BMP-driven transcriptional signatures and key players associated with primate amniotic ectoderm specification.