Border cells contribute to an early placental structure in mice
Cells near a boundary in the mouse embryo's outer layer contributed to an early placental structure previously attributed to another region alone. A peer-reviewed study combined cell measurements and live imaging to track that contribution. Cultured human embryos showed regional differences too, but the same developmental contribution has not been established in humans.
Science··Morning
An early placental precursor has two cellular origins
Some cells at the boundary of the mouse embryo's outer layer joined the ectoplacental cone, an early placental precursor. That structure had previously been attributed to polar trophectoderm alone. Live tracking identified a contribution from neighbouring mural trophectoderm, extending the developmental account of how this tissue forms around implantation. The peer-reviewed study combined single-cell measurements, tissue imaging and functional experiments rather than relying on cell appearance alone.[1]
Border cells changed position during implantation
The mouse atlas spans six stages and includes 15 cell types across a total of 22,171 cells. Border mural cells expressed a marker associated with the cone before relocating. Removing mural tissue impaired normal cone formation, supporting its contribution. Uterine contact was closely associated with the border-cell identity. How those cells move remains unresolved: active migration, displacement as neighbouring tissues change shape, or a combination could account for their relocation.[1]
Human observations do not yet establish the same lineage
Cultured human embryos also showed different behaviour between mural cells near and far from the border. The organization of human trophoblast differs markedly from its mouse counterpart, so contributions to particular human cell subtypes in living development remain unproven. The donated embryos differed in their developmental potential and quality; only embryos that attached in culture entered the analyses. The findings may help explain weaknesses in stem-cell embryo models lacking a mural compartment; they do not establish a fertility treatment's success or harm from human embryo biopsy.[1]
