ATAC-seq provides the open chromatin landscape of LT-HSCs, ST-HSCs, and MPPs. (A) Representative flow cytometry results to assess the Sca1⁺c-Kit⁺ population of cells, then to further distinguish LT-HSCs, ST-HSCs, and MPPs using the CD150 and CD48 combination of markers. (B) PCA for read counts of bins genome-wide among ATAC-seq samples. (C) Scatterplot and Pearson correlation of ATAC-seq data between 2 biological replicates for each of the 3 HSC cell types (LT-HSCs, ST-HSCs, and MPPs). (D-F) Browser track plot of ATAC-seq signal (RPM) in the genomic regions around CD34, Flt3/Flk2, and Hoxb5, respectively. (G) Gene expression activity of CD34, Flt3/Flk2, and Hoxb5 in different types of blood cells. Expression data collected from Gene Expression Commons (https://gexc.stanford.edu). Gene expression activity ranged from −100 (most inactive) to 100 (most active). MEP, megakaryocyte-erythroid progenitor.