Exploring the first lineage segregation in the human embryo: is GATA3 the gatekeeper of trophectoderm differentiation?

In mammalian preimplantation development the differentiation of
blastomeres into trophectoderm (TE) and inner cell mass (ICM) in the
blastocyst represents the first lineage segregation. Knowledge
regarding this event in the human embryo is scarce and data from
mouse models cannot be fully extrapolated. Neither the timing of
lineage segregation during preimplantation development nor the
molecular determinants are known. Here we aim to investigate the
role of polarity dependent TEAD/YAP1 interaction in the induction of
TE specific GATA3 expression in the outer cells of the early human
embryo. In a first step we will use a novel approach of a single-cell
RNA-seq pseudotime modelling to investigate the spatial and
temporal distribution of pluripotency factors OCT4, SOX2 and
NANOG and TE markers CDX2 and GATA3 to define the onset and
duration of TE differentiation. To characterize the role of GATA3 we
will use CRISPR/Cas9 technology to knockout GATA3 as well as
novel inhibitors to block TEAD/YAP1 interaction to identify how this
interaction regulates GATA3 expression. In a last step we will
attempt to investigate the contribution of GATA3 to cell differentiation
and plasticity by manipulating the position of the blastomeres. We
expect to identify and confirm GATA3 as the gatekeeper of TE
differentiation and further increase our knowledge of human
preimplantation development to improve artificial reproductive
techniques.