Transcription Landscape Analysis of Wild Type and HHEX-/- ES-derived Pancreatic Progentiors

The pancreas and liver arise from a common pool of progenitors in the foregut endoderm; however, the underlying molecular mechanisms driving this lineage diversification are not fully understood. We combined human pluripotent stem cell guided differentiation and sequential CRISPR-Cas9 loss-of-function screening to uncover regulators of pancreatic specification. Here we report the discovery an unexpected, cell-intrinsic requirement for HHEX, a transcription factor (TF) associated with diabetes susceptibility. HHEX promotes pancreatic differentiation through cooperation with pancreatic TFs as well as common TFs like FOXA2 that are shared by both pancreas and liver differentiation programs. Furthermore, HHEX restricts differentiation plasticity, and deletion of HHEX causes a shift of FOXA2 interaction towards cooperation with HNF4A to drive liver differentiation. Our findings demonstrate a critical role for the fine tuning of TF cooperation in organ domain demarcation, as exemplified by how HHEX safeguards pancreatic differentiation by simultaneously promoting lineage specification and restricting cell fate plasticity. Overall design: RNA-seq at various stages of ES-derived pancreatic progenitor differentiation in the context of WT and HHEX KO