NIH Research Festival
FARE Award Winner
Enhancers are cis-regulatory elements controlling cell-type-specific gene expression and are marked by H3K4me1. MLL3 (KMT2C) and MLL4 (KMT2D), the major mammalian H3K4me1 methyltransferases, are critical for enhancer activation and cell-type-specific transcription during development and cell differentiation. However, roles of MLL3/4 enzymatic activities and MLL3/4-mediated enhancer H3K4me1 in these processes remain unclear.
Using MLL3/4 enzyme-dead single and double knockin mice generated by CRISPR/Cas9, we report that enzymatic activities of MLL3 and MLL4 are redundant during early embryonic development. Simultaneous elimination of both leads to gastrulation failure and early embryonic lethality around E6.5. Embryonic stem cells (ESCs) lacking MLL3/4 enzymatic activities can differentiate towards the three embryonic germ layers including endoderm, mesoderm and ectoderm. However, they fail to differentiate to extraembryonic endoderm cells due to markedly reduced enhancer binding of GATA6, the lineage-determining transcription factor driving extraembryonic endoderm development. Moreover, loss of MLL3/4 enzymatic activity blocks induction of Elf5 during ESC to trophectoderm transition and thus leads to precocious terminal trophoblast differentiation. Consistent with ESC data, Sox2-Cre-mediated elimination of MLL3/4 enzymatic activities in epiblast, but not in early extraembryonic tissues, leaves gastrulation largely intact. These conditional MLL3/4 enzyme-dead mice survive until mid-gestational stage beyond E10.5. Furthermore, we show that MLL3/4-catalyzed H3K4me1 is largely dispensable for enhancer activation during early EB differentiation and neural differentiation of ESCs. Together, our findings highlight a lineage-selective, but enhancer activation-independent, role of MLL3/4 methyltransferase activities in mammalian embryonic development and ESC differentiation.
Scientific Focus Area: Genetics and Genomics
This page was last updated on Monday, September 25, 2023