Enhancers drive cell-type-specific gene transcription and are marked by H3K4me1. MLL4 (KMT2D), a major H3K4me1 methyltransferase with partial functional redundancy with MLL3 (KMT2C), is critical for enhancer activation and cell-type-specific gene induction during cell differentiation and development. However, the roles of MLL3/4-mediated enhancer H3K4me1 and MLL3/4 enzymatic activities in general in these processes remain unclear. Here, we report that MLL3/4 enzymatic activities are partially redundant during mouse development. Simultaneous elimination of both leads to embryonic lethality around E8.5. Using embryoid body (EB) differentiation as an in vitro model for early embryonic development, we show that Mll3 knockout MLL4 enzyme-dead embryonic stem cells (ESCs) are capable of differentiating towards the three germ layers but display severe cavitation defects, likely due to impaired induction of visceral endoderm. Importantly, MLL3/4-catalyzed H3K4me1 is dispensable for enhancer activation during early EB differentiation and lineage-specific neural differentiation. Together, these results suggest a critical, but enhancer H3K4me1-independent, role of MLL3/4 enzymatic activities in early embryonic development and ESC differentiation.
ES cell differentiation system recapitulates the establishment of imprinted gene expression in a cell-type-specific manner