HAND1 controls the lineage bifurcation of trophoblast and amnion from human pluripotent stem cells.

Trophoblast and amniotic lineages, representing key extra-embryonic tissues, can be differentiated from human pluripotent stem cells (hPSCs) under chemically defined conditions. However, the regulatory mechanisms coordinating the fate decision between these lineages during PSC differentiation remain incompletely understood. Leveraging CRISPR/Cas9-mediated loss-of-function screening in lineage-reporter PSCs, we identified the transcription factor HAND1 as a critical determinant controlling the bifurcation of trophoblast and amniotic lineages. Genetic ablation of HAND1 effectively abrogated the amniotic differentiation capacity of PSCs while concomitantly enhancing their trophoblast differentiation potential. Conversely, ectopic HAND1 overexpression impaired trophoblast differentiation. Notably, forced HAND1 expression in human trophoblast stem cells (TSCs) induced transcriptional reprogramming toward an amniotic fate, indicating its lineage-instructive capability. Mechanistic analyses demonstrated that HAND1 interacts with the TCFs and Wnt signaling effectors β-catenin to form a transcriptional complex that antagonistically modulates the balance between trophoblast- and amnion-associated gene regulatory networks. Collectively, our findings establish HAND1 as a master regulator orchestrating the amniotic versus trophoblast lineage choice during human PSC differentiation, thereby illuminating fundamental regulatory mechanism underlying extra-embryonic lineage specification.