The role of Arid4b in mESC lineage commitment (RNA-Seq)
Distinct cell types emerge from embryonic stem cells through a precise and coordinated execution of gene expression programs during lineage commitment. This is established by the action of lineage specific transcription factors along with chromatin complexes. Numerous studies focused on epigenetic factors that affect ESC self-renewal and pluripotency. However, the contribution of chromatin to lineage decisions at the exit from pluripotency has not been studied extensively. We have set out to identify chromatin related factors critical for differentiation towards mesodermal and endodermal lineages. Our results reveal a critical role for chromatin protein, Arid4b. Arid4b deficient mESCs are similar to wild-type mESCs in the expression of pluripotency factors and their self-renewal. However, we found that Arid4b loss results in defects in upregulation of meso/endodermal gene expression program. Arid4b is in the Sin3a complex along with Hdac1 and Hdac2. We identified a physical and functional interaction of Arid4b with Hdac1 rather than Hdac2. Arid4b deficiency leads to changes in the overall chromatin environment. Most notably, a subset of the genomic loci was found to gain H3K27Ac whereas several of the key developmental genes instead have increased H3K27me3 levels. Accordingly, the super-enhancers associated with meso/endoderm commitment were selectively reduced in arid4b? cells. Overall design: arid4b?  vs. wild type