Human trophectoderm becomes multi-layered by internalisation at the polar region

Elena Corujo Simon*, Lawrence Bates, Ayaka Yanagida, Kenneth Jones, Stephen Clark, Ferdinand von Meyenn, Wolf Reik, Jennifer Nichols*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

To implant in the uterus, mammalian embryos form blastocysts comprising trophectoderm
surrounding an inner cell mass, confined to the polar region by the expanding blastocoel. The
mode of implantation varies between species. Murine embryos maintain a single layered
trophectoderm until they implant in the characteristic thick deciduum, whereas human
blastocysts attach via polar trophectoderm directly to the uterine wall. Using
immunofluorescence of rapidly isolated inner cell masses, blockade of RNA and protein
synthesis in whole embryos, or 3D visualisation of immunostained embryos we provide
evidence of multi-layering in human polar trophectoderm before implantation. This may be
required for rapid uterine invasion to secure the developing human embryo and initiate
formation of the placenta. Using sequential fluorescent labelling, we demonstrate that the
majority of inner trophectoderm in human blastocysts arises from existing outer cells with no
evidence of conversion from the inner cell mass in the context of the intact embryo
Original languageEnglish
JournalDevelopmental Cell
Publication statusPublished - 17 Jun 2024

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