Enhancer commissioning by H3K4 methyltransferase MLL4 regulates ES cell pluripotency and cell reprogramming

Friday, November 08, 2013 — Poster Session III
10:00 a.m. – 12:00 p.m.	FAES Academic Center (Upper-Level Terrace)	NIDDK	CHROM-9

Authors

C Wang
S Xu
JE Lee
YW Cho
T Macfarlan
K Cui
C Liu
W Peng
K Ge

Abstract

In eukaryotes, enhancers are marked by mono- and di-methylation of histone H3 lysine 4 (H3K4me1/2). Active enhancers are further marked by acetylation on histone H3 lysine 27 (H3K27ac). However, the methyltransferases responsible for H3K4me1/2 on mammalian enhancers have remained elusive. Here we show that MLL4 is a major H3K4 mono- and di-methyltransferase in mouse ESCs. ChIP-Seq analysis in ESCs reveals that MLL4 is enriched on enhancers and co-localizes with pluripotency circuitry transcription factors Sox2 and Oct4 on enhancers. Deletion of MLL4 in ESCs eliminates H3K4me1/2 and attenuates H3K27ac on MLL4-positive enhancers, indicating that MLL4 is required for enhancer activation. Further analysis of direct MLL4 target genes identifies multiple Oct4-regulated genes important for ESC pluripotency. Deletion of MLL4 impairs activation of Oct4-binding enhancers on these genes and leads to decreased gene expression. Consistently, MLL4 is required not only for maintaining ESC identity but also for reprogramming of somatic cells into induced pluripotent cells (iPSCs). Finally, MLL4 knockout ESCs also show severe defects in differentiation towards mesoderm and endoderm, indicating that MLL4 is required for ESC pluripotency. Our results thus identify an essential role of H3K4 mono- and di-methyltransferase MLL4 in enhancer commissioning on genes critical for establishing and maintaining ESC pluripotency.