VGLL1 cooperates with TEAD4 to control human trophectoderm lineage specification [scRNA-Seq]

In contrast to rodents, the mechanisms underlying human trophectoderm and early placenta specification are understudied due to ethical barriers and the scarcity of embryos. Recent reports have shown that human pluripotent stem cells (PSCs) can differentiate into trophectoderm (TE)-like cells (TELCs) and trophoblast stem cells (TSCs), offering a valuable in vitro model to study early placenta specification. Here, we demonstrate that the VGLL1 (vestigial-likefamilymember1), which is highly expressed during human and non-human primate TE specification in vivo but is negligibly expressed in mouse, is a critical regulator of cell fate determination and self-renewal in human TELCs and TSCs derived from naïve PSCs. Mechanistically, VGLL1 partners with the transcription factor TEAD4 (TEA domain transcription factor 4) to regulate chromatin accessibility at target gene loci through histone acetylation and acts in cooperation with GATA3 and TFAP2C. Our work is relevant to understand primate early embryogenesis and how it differs from other mammalian species. Overall design: Human naïve PSCs were dissociated into single cells with a 1:1 mixture of 0.5 mM EDTA and TrypLE Express and plated at a density of 100,000 cell/well of 6-well plate on Geltrex in TE induction medium (1:1 mix of Neurobasal medium (Gibco) and DMEM/F12 (HyClone) supplemented with N2 (Gibco) and B27 (Gibco), penicillin-streptomycin (HyClone), Glutamax (Gibco), ß-mercaptoethanol (Sigma), 1 µM PD0325901 (Axon) and 1 µM A83-01 (Selleck)) for five days. TELCs at day 5 were used for downstream analysis throughout this study. For generating expandable TSCs, TELCs at day 5 were dissociated into single cells with TrypLE and plated on Geltrex-coated six-well plates at a 1:4-1:8 split ratio in TSC medium (DMEM/F12 supplemented with N2 and B27, penicillin-streptomycin, Glutamax, ß-mercaptoethanol, 1.5 µg/ml L-ascorbic acid, 50 ng/ml EGF (PeproTech), 0.5 µM A83-01 (Selleck), 1 µM SB431542 (Selleck), 2 µM CHIR99021 (Axon), 0.8 mM VPA (Vetec) and 5 µM Y-27632 (Axon)) supplemented with 10 µM Y-27632.