Project description:We describe an assay for transposase-accessible chromatin using sequencing (ATAC-seq), based on direct in vitro transposition of sequencing adaptors into native chromatin, as a rapid and sensitive method for integrative epigenomic analysis. ATAC-seq captures open chromatin sites using a simple two-step protocol with 1000–50,000 cells and reveals the interplay between genomic locations of open chromatin, DNA-binding proteins, individual nucleosomes and chromatin compaction at nucleotide resolution. We discovered classes of DNA-binding factors that strictly avoided, could tolerate or tended to overlap with the nucleosome. Using ATAC-seq maps of chromatin accessibility in Irf8+/+ and Irf8-/- LT-HSC cells, we demonstrated the genome-wide activity of cis-regulatory elements (CREs) perturbation in IRF8 deficient mice bone marrow LT-HSC.
Project description:The transcriptome of Ctrl and Vitamin A-deficient longterm hematopoietic stem cells (LT-HSC) and multipotant progenitors (MPP3/4) was assessed by RNAseq.
Project description:Life-long blood production requires long-term hematopoietic stem cells (LT-HSC) - marked by stemness states involving quiescence and self-renewal - to transition into activated short-term HSC (ST-HSC) with reduced stemness. As few transcriptional changes underlie this transition, we used single-cell and bulk ATAC-seq on human HSC and stem/progenitor subsets (HSPC) to uncover chromatin accessibility signatures, one including LT-HSC (LT/HSPC signature) and another excluding LT-HSC (Act/HSPC signature). These signatures inversely correlated during early hematopoietic commitment and differentiation. The Act/HSPC signature contains CTCF binding sites mediating 351 chromatin interactions, engaged in ST-HSC but not LT-HSC, enclosing multiple stemness pathway genes active in LT-HSC and repressed in ST-HSC. CTCF silencing derepressed stemness genes, restraining quiescent LT-HSC from transitioning to activated ST-HSC. Hence, 3D chromatin interactions centrally mediated by CTCF, endow a gatekeeper function that governs the earliest fate transitions HSC make by coordinating disparate stemness pathways linked to quiescence and self-renewal.
Project description:To investigate how ex vivo culture affects chromatin accessibility in cultured HSC, we performed the Assay for Transposase Accessible Chromatin with high-throughput sequencing (ATAC-Seq) on cLT (CD34+CD90+CD45RA-) and cST populations purified from 8 day cultured lineage depleted cord blood (lin- CB) cells treated with 3-Factor (4HPR+UM171+SR1), U+S or 4HPR as well as untreated and vehicle-treated (DMSO) control populations. The subsequent ATAC-seq data was compared to chromatin accessibility signatures generated from uncultured hematopoietic stem and progenitor populations (Takayama, et al.). We found that ex vivo culture shifted cLT and cST cells isolated from control or untreated samples to a chromatin accessibility profiles not found in LT-HSC, suggesting some loss of a stem-cell associated chromatin state. By contrast, 4HPR-treated, to some extent, and 3-Factor-treated HSC maintained chromatin accessibility features of uncultured LT-HSC.
