Single cell lineage analysis reveals extensive multimodal transcriptional control during directed β-cell differentiation

The in vitro differentiation of insulin-producing β-like cells can model aspects of human pancreatic development. Here we generate 95,308 single cell transcriptomes and reconstruct a lineage tree of the entire differentiation process from hESCs to β-like cells to study temporally regulated genes during differentiation. We identify so-called ‘switch genes’ at the branch point of endocrine/non-endocrine cell fate choice, revealing insights into the mechanisms of differentiation promoting reagents, such as NOTCH and ROCKII inhibitors, and providing improved differentiation protocols. Over 20% of all detectable genes are activated multiple times during differentiation, even though their enhancer activation is usually unimodal, indicating extensive gene reuse driven by different enhancers. We also identify a stage-specific enhancer in the TCF7L2 diabetes GWAS locus that drives a transient wave of gene expression in pancreatic progenitors. Finally, we develop a web app to visualize gene expression on the lineage tree, providing a comprehensive single cell data resource for researchers studying islet biology and diabetes.