RNA-seq of bulk trophectoderm microdissected from human blastocysts cultured to day 5, day 6 and day 7 post-fertilisation
5 days after fertilisation the human embryo forms a blastocyst, comprising an outer layer of trophectoderm (TE), that gives rise to placental trophoblast cells, and the inner cell mass (ICM) which later segregates into epiblast (EPI) and primitive endoderm (PE). After implantation TE differentiates into cytotrophoblast cells (CTBs) which give rise to the multinucleated syncytiotrophoblast (STB) and invasive extravillous trophoblast cells (EVTs). A conserved molecular cascade regulates TE initiation (Gerri et al. Nature 2020), but subsequent TE development is poorly defined. To study this in greater detail we performed RNA-seq analysis of human blastocysts cultured to different stages of pre-implantation TE development: Day 5: TE appearance, Day 6: TE expansion and Day 7: TE hatching.