Project description:Chromatin organization is a highly orchestrated process that influences gene expression, in part by modulating access of regulatory factors to DNA and nucleosomes. We found that the chromatin accessibility regulator HMGN1, a target of recurrent DNA copy gains in leukemia, controls myeloid differentiation. HMGN1 amplification was associated with increased accessibility, expression, and histone H3K27 acetylation of loci important for hematopoietic stem cell (HSC) function and AML, such as HoxA cluster genes. In vivo, HMGN1 overexpression was linked to decreased quiescence and increased HSC activity in bone marrow transplantation. HMGN1 overexpression also cooperated with the AML-ETO9a fusion oncoprotein to impair myeloid differentiation and enhance leukemia stem cell (LSC) activity. Inhibition of histone acetyltransferases CBP/p300 relieved the HMGN1-associated differentiation block. These data nominate factors that modulate chromatin accessibility as regulators of HSCs and LSCs and suggest that targeting HMGN1 or its downstream effects on histone acetylation could be therapeutically active in AML.
Project description:Tissue homeostasis and regeneration require activation and subsequent lineage commitment of tissue-resident stem cells (SCs). These state changes are controlled by epigenetic barriers. Using hair follicle stem cells (HFSCs) as paradigm, we studied how aging impacts the chromatin landscape and function of mammalian SCs. Analyses of genome-wide chromatin accessibility revealed that aged HFSCs displayed widespread reduction of chromatin accessibility specifically at key SC self-renewal and differentiation genes that were characterized by bivalent promoters carrying both activating and repressive chromatin marks. Consistently, aged HFSCs showed reduced self-renewing capacity and attenuated ability to activate expression of these bivalent genes upon regeneration. These functional defects were niche-dependent as transplantation of aged HFSCs into young recipients or into ex vivo niches restored SC functions and transcription of poised genes. Mechanistically, aged HFSC niche displayed wide-spread alterations in extracellular matrix composition and mechanics, resulting in compressive forces on SCs and subsequent transcriptional repression, leading to loss of bivalent promoters. Tuning tissue mechanics both in vivo and in vitro recapitulated age-related SC changes, implicating niche mechanics as a central regulator of genome organization and function leading to age-dependent SC exhaustion.
Project description:Epithelial-mesenchymal transition (EMT), the process whereby cells gain migratory and invasive properties characteristic of mesenchymal cells, plays a central role in embryogenesis and wound healing in a wide range of tissues. However, EMT has also been linked to the formation of cancer stem cells (CSCs). Many of the signaling pathways involved in EMT have also been implicated in CSC formation but the processes that contribute uniquely to CSC formation remain elusive. We have previously demonstrated that PKCθ activation is critical for EMT induction and concomitant CSC formation in the breast cancer luminal epithelial cell line, MCF7. To discover how PKC-induced alterations in the epigenome influence the EMT and CSC formation in MCF-7 cells, we employed a combination of expression profiling and Formaldehyde Assisted Regulatory Elements (FAIRE)-sequencing in order to reveal novel links between gene expression and DNA accessibility changes after PKCθ activation. We found that, during EMT, increases in accessibility generally occurred in regions away from transcription start sites, low in CpG, enriched with chromatin marks of enhancer elements and motifs for FOX, AP1, TEAD and AP2. Increases in FOX and AP-1 motif accessibility were associated with genes that exhibited increased expression in CSC, while increased AP-2 accessibility was associated with genes that had higher expression in non-CSCs. This study revealed novel regions of DNA accessibility induced by PKC that contribute to the understanding of how epigenomic plasticity of cells undergoing EMT leads to the activation of genes that drive the CSC program. 2 biological samples were analysed with 2 biological replicates each and a mixed total input.
Project description:<p>Non-coding regions comprise most of the human genome and harbor a significant fraction of risk alleles for neuropsychiatric diseases, yet their functions remain poorly defined. We created a high-resolution map of non-coding elements involved in human cortical neurogenesis by contrasting chromatin accessibility and gene expression in the germinal zone and cortical plate of the developing cerebral cortex. To obtain a high resolution depiction of chromatin structure and gene expression in developing human fetal cortex, we dissected the post-conception week (PCW) 15-17 human neocortex into two major anatomical divisions to distinguish between proliferating neural progenitors and post mitotic neurons: (1) GZ: the neural progenitor-enriched region encompassing the ventricular zone (VZ), subventricular zone (SVZ), and intermediate zone (IZ) and (2) CP: the neuron-enriched region containing the subplate (SP), cortical plate (CP), and marginal zone (MZ). Tissues were obtained from three independent donors and three to four technical replicates from each tissue were processed for ATAC-seq to define the landscape of accessible chromatin and RNA-seq for genome-wide gene expression profiling.</p>
Project description:A single hematopoietic stem cell can give rise to all blood cells with remarkable fidelity. Here, we define the chromatin accessibility and transcriptional landscape controlling this process in thirteen primary cell types that traverse the hematopoietic hierarchy. Exploiting the finding that enhancer landscapes better reflect cell identity than mRNA levels, we enable "enhancer cytometry" for accurate enumeration of pure cell types from complex populations. We further reveal the lineage ontogeny of genetic elements linked to diverse human diseases. In acute myeloid leukemia, chromatin accessibility reveals distinctive regulatory evolution in pre-leukemic HSCs (pHSCs), leukemia stem cells, and leukemic blasts. These leukemic cells demonstrate unique lineage infidelity, confirmed by single cell regulomes. We further show that pHSCs have a competitive advantage that is conferred by reduced chromatin accessibility at HOXA9 targets and is associated with adverse patient outcomes. Thus, regulome dynamics can provide diverse insights into human hematopoietic development and disease. Single-cell ATAC-seq of LMPPs, Monocytes, LSCs and Luekemic blast cells.
Project description:Mesenchymal stem cells (MSCs) are multipotent stem cells that are under investigation for use in clinical trials because they are capable of self-renewal and differentiating into different cell types under defined conditions. Nonetheless, the therapeutic effects of MSCs have been constrained by low engraftment rates, cell fusion, and cell survival. Various strategies have been explored to improve the therapeutic efficacy of MSCs, with platelet-derived growth factor (PDGF)-BB emerging as a promising candidate. To enhance our comprehension of the impact of PDGF-BB on the gene expression profile and chromosomal accessibility of MSCs, RNA-sequencing and analysis of chromatin accessibility profiles were conducted on three human primary MSCs in culture, both with and without stimulation by PDGF-BB. Integrative analysis of gene expression and chromatin accessibility demonstrated that PDGF-BB treatment modified the chromatin accessibility landscape, marking regions for activation or repression through the AP-1 family transcription factors TEAD, CEBP, and RUNX2. These changes in AP1 transcription factor expression, in turn, led to cell proliferation and differentiation potential towards osteoblasts, adipocytes, or chondrocytes. The degree of MSC differentiation varies among cells isolated from different donors. The presence of an enrichment of exosome-related genes is also noted among all the differentially expressed genes. In conclusion, the observed changes in AP1 transcription factor expression not only induced cellular proliferation and differentiation, but also revealed variations in the degree of MSC differentiation based on donor-specific differences. Moreover, the enrichment of exosome-related genes among differentially expressed genes suggests a potential significant role for PDGF-BB in facilitating intercellular communication.
Project description:Loss-of-function mutations in genes coding for subunits of the large, multifarious BRG1/BRM associated factor (BAF) chromatin remodeling complexes are frequently causative for cancer or developmental diseases1-5. Cells lacking the most frequently mutated subunits like the ATPase SMARCA4 typically exhibit drastic chromatin accessibility changes, especially of important regulatory regions6-12. However, so far it remains unknown how these changes are established over time, and whether they are causative for intra-complex synthetic lethalities abrogating the formation (SMARCC1-SMARCC2)8,13,14 or activity (SMARCA4-SMARCA2)15-17 of BAF complexes. Here, we utilize the dTAG system18 to induce acute degradation of BAF subunits in wild-type and BAF mutant backgrounds and analyze the resulting chromatin accessibility changes with high kinetic resolution. We observe that chromatin alterations are established faster than the duration of one cell cycle and that maintaining genome accessibility requires constant ATP-dependent remodeling. Completely abolishing BAF complex function by acute degradation of a synthetic lethal subunit in a paralog-deficient background results in a near-complete loss of chromatin accessibility at BAF-controlled sites, especially at super-enhancers, providing a mechanism for intra-complex synthetic lethalities.