Haematopoietic stem cells (HSC) and multipotent progenitors (MPP) generate all cells of the blood system. Despite their multipotency, MPPs display poorly understood lineage bias. Here, we examine whether lineage-specifying transcription factors, such as the B-lineage determinant EBF1, regulate lineage preference in early progenitors. We detect low level EBF1 expression in myeloid-biased MPP3 and lymphoid-biased MPP4 cells, coinciding with expression of the myeloid determinant C/EBPα. Hematopoietic deletion of Ebf1 results in enhanced myelopoiesis and reduced HSC repopulation capacity. Ebf1-deficient MPP3 and MPP4 cells exhibit augmented myeloid differentiation potential and a myeloid-enriched transcriptome that is inversely correlated with Cebpa-deficient progenitors. Correspondingly, EBF1 binds the Cebpa enhancer and Ebf1-deficient MPP3 and MPP4 cells upregulate Cebpa expression. In addition, EBF1 primes the chromatin of B-lymphoid enhancers specifically in MPP3 cells. Thus, our study implicates EBF1 in regulating myeloid/lymphoid fate bias in MPPs by constraining C/EBPα -driven myelopoiesis and priming the B-lymphoid fate.

Included is the data, scripts and container (singularity) for the single-cell RNA-seq analysis, Lenaerts_et_al_scRNA_data.tar.gz. ATAC-seq data are included in the Lenaerts_et_al_ATAC_LFS.tar.gz file.