Primitive Syncytiotrophoblast Cells (ChrF)

In the mouse, the closest equivalent of this cell type is the secondary trophoblast giant cells (TGCs), which are terminally differentiated polyploid cells that are formed by endoreduplication and possess invasive properties, which mediate invasion of the conceptus into the maternal decidua. They of are diverse origins, with a first wave of primary TGCs arising from mural trophectoderm cells, whereas subsequent secondary giant cells arise from the ectoplacental cone progenitor cells, and may also directly arise from the chorion.