An integrated global regulatory network of hematopoietic precursor cell self-renewal and differentiation

The mammalian blood system is a hierarchically structured tissue. Hematopoietic stem cells (HSC) reside at the top of this hierarchy and the HSC-derived progenitor cells (HPC) have capacities for both differentiation and self-renewal. Systematic study of the regulatory mechanisms of HSC self-renewal and differentiation is fundamentally important for understanding hematopoiesis and for manipulating HSCs for therapeutic purposes. Herein, the mechanisms regulating HSC biology were studied on a genome-wide scale by integrating epigenomic, transcriptomic, proteomic, and protein-protein interaction data. Previously, we have characterized gene expression and identified important transcription factors (TFs) regulating the switch between self-renewal and differentiation in a multipotent hematopoietic progenitor cell line, EML (Erythroid, Myeloid, and Lymphoid). In the present study, we report binding maps for three additional TFs (SOX4, STAT3, and GABP) that were developed by chromatin immunoprecipitation (ChIP)-Sequencing. Assay for Transposase Accessible Chromatin (ATAC)-Sequencing was applied to globally identify the open chromatin regions associated with TF binding in the self-renewing subpopulation lin-CD34+.Mass spectrometry (MS) was also used to identify proteins and assess differences in their relative abundances. We found that MAPK (Mitogen-activated protein kinase) pathway and JAK-STAT (Janus kinase-signal transducer and activator of transcription) pathway components were highly enriched among the binding targets of these TFs in CD34+ cells, and that the TGF-β/SMAD signaling pathway comprised a sub-network of molecules that were differentially expressed between the lin-CD34+ and partially differentiated lin-CD34- cellular states. The present study integrates regulatory information at multiple levels to paint for the first time a more comprehensive picture of the mechanisms underlying the decision between HPC self-renewal and differentiation. We anticipate that this work will provide valuable clues for understanding the molecular switch that controls cell fate decisions between self-renewal or differentiation and blood formation. In vivo binding targets of transcription factors STAT3, SOX4, and GABPa were found through ChIP-sequencing in lin-CD34+ and lin-CD34- cells. Additionally, open chromatin regions were studied through ATAC-seq sequencing in lin-CD34+ cells. Epigenetic, transcriptomic, and proteomic data were integrated into a regulatory network.