Requisite chromatin remodeling for myeloid and erythroid lineage differentiation from erythromyeloid progenitors

The mammalian SWI/SNF chromatin-remodeling BAF (BRG1/BRM associated factor) complex plays an essential role in developmental and pathological processes. We show that the deletion of Baf155 encoding a subunit of BAF complex in the Tie2(+) lineage (Baf155 CKO) leads to defects in the yolk sac myeloid and definitive erythroid (EryD) lineage differentiation from erythromyeloid progenitors (EMPs) and embryonic lethality. Baf155 knock-down in EMP was sufficient to block myeloid and EryD differentiation. Chromatin of the myeloid gene loci in Baf155 CKO EMPs was largely inaccessible and was enriched mostly by the ETS binding motif. BAF155 interacted with PU.1 and was recruited to the PU.1 in target gene loci together with p300 and KDM6a. Treatment of Baf155 CKO embryos with GSK126, an inhibitor of the H3K27me2/3 methyltransferase EZH2, rescued myeloid lineage gene expression. These studies uncover the indispensable BAF mediated chromatin remodeling of the myeloid gene loci at the EMP stage. Droplet-based 5′ end massively parallel single-cell RNA sequencing was performed by isolating single nuclei from mouse yolk sac and libraries were prepared using Chromium 10x Genomics library construction. The generated scRNAseq libraries were sequenced using HiSeq2500 sequencers. Equal numbers of mouse E9.5 and E10.5 per genotypes were mixed and dissociated. Dead cells and Ter119+ cells were excluded by sorting to enrich live and non-erythroid cells that proceed to sequence.