|Human embryo Carnegie Stage 5c (Carnegie Embryo #7700)|
Photomicrograph courtesy of Dr. Allen C. Enders
Papers by two groups were just published: Shahbazi et al. in Nature Cell Biology and Deglincerti et al. in Nature. They used appropriate molecular markers to identify epiblast, primitive endoderm (hypoblast) and trophectoderm. In addition they used cytokeratin 7 and human chorionic gonadotrophin as markers for cyto- and syncytiotrophoblast.
|Day 13 embryo of the rhesus macaque (Macaca mulatta) |
Courtesy of Dr. Allen C. Enders
As in the macaque, amnion formation was by cavitation. This is nicely described by Shahbazi et al. Unfortunately they use the term pro-amnion, which is appropriate in the mouse but not in primates (contrasted here).
Differentiation of trophectoderm into cytotrophoblast and multinucleated syncytiotrophoblast was confirmed with appearance of lacunae in the latter as appropriate for Carnegie Stage 5c.