Epigenetic Restoration of Fetal-like IGF1 Signaling Inhibits Leukemia Stem Cell Activity

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Epigenetic regulation in normal hematopoiesis and its dysfunction in leukemia

Epigenetic modifications including reversible and non-uniform chemical marks to chromatin support activation and silencing of gene transcription. Alterations in normal epigenetic states are associated with transformation across a wide range of cancer types including myeloid malignancies. To understand the role of epigenetic regulation of normal human hematopoietic progenitors and its dysfunction in myeloid transformation, I developed a low-cell input chromatin immunoprecipitation method that, when combined with an analytical framework enables a simultaneous assessment of chromatin accessibility and histone modification state. This method enabled a comparative analysis of the epigenomic states of normal and malignant human blood cell compartments. Application of this methodology to highly purified, phenotypically defined subsets of primitive and terminally differentiating normal human cord blood cells showed that multiple human hematopoietic progenitor phenotypes display a common H3K27me3 signature. This signature includes many large organized H3K27me3 domains co-marked by H3K9me3 also found in the mature lymphoid cells in cord blood (CB) but not in co-isolated monocytes or erythroblasts. These results indicate a marked difference in the epigenomic changes primitive human neonatal hematopoietic cells undergo when they initiate terminal differentiation of the lymphoid and myeloid lineages. Further evidence that this differential H3K27me3 contraction directly impacts hematopoietic differentiation was obtained by manipulating H3K27me3 regulators in cell line models of inducible neutrophil differentiation in vitro. These methodologies were then used to explore epigenomic dysfunction found in the leukemic cells obtained from patients presenting with acute myeloid leukemia (AML) whose blasts differed in their content of neomorphic isocitrate dehydrogenase (IDH) mutations. Comparison of the methylation landscape in the AML cells with and without IDH mutations revealed a higher fractional DNA methylation level at active enhancers in the IDH mutant cells. However, there was no significant difference in global occupancy of histone modifications between the leukemic cells from the two patient groups. Collectively, these findings reveal previously unknown relationships of epigenetic modifications in normal and malignant human blood cells.Science, Faculty ofMicrobiology and Immunology, Department ofGraduat

Capacitor Current Feedback-Based Active Resonance Damping Strategies for Digitally-Controlled Inductive-Capacitive-Inductive-Filtered Grid-Connected Inverters

Inductive-capacitive-inductive (LCL)-type line filters are widely used in grid-connected voltage source inverters (VSIs), since they can provide substantially improved attenuation of switching harmonics in currents injected into the grid with lower cost, weight and power losses than their L-type counterparts. However, the inclusion of third order LCL network complicates the current control design regarding the system stability issues because of an inherent resonance peak which appears in the open-loop transfer function of the inverter control system near the control stability boundary. To avoid passive (resistive) resonance damping solutions, due to their additional power losses, active damping (AD) techniques are often applied with proper control algorithms in order to damp the LCL filter resonance and stabilize the system. Among these techniques, the capacitor current feedback (CCF) AD has attracted considerable attention due to its effective damping performance and simple implementation. This paper thus presents a state-of-the-art review of resonance and stability characteristics of CCF-based AD approaches for a digitally-controlled LCL filter-based grid-connected inverter taking into account the effect of computation and pulse width modulation (PWM) delays along with a detailed analysis on proper design and implementation

Polycomb contraction differentially regulates terminal human hematopoietic differentiation programs

Background Lifelong production of the many types of mature blood cells from less differentiated progenitors is a hierarchically ordered process that spans multiple cell divisions. The nature and timing of the molecular events required to integrate the environmental signals, transcription factor activity, epigenetic modifications, and changes in gene expression involved are thus complex and still poorly understood. To address this gap, we generated comprehensive reference epigenomes of 8 phenotypically defined subsets of normal human cord blood. Results We describe a striking contraction of H3K27me3 density in differentiated myelo-erythroid cells that resembles a punctate pattern previously ascribed to pluripotent embryonic stem cells. Phenotypically distinct progenitor cell types display a nearly identical repressive H3K27me3 signature characterized by large organized chromatin K27-modification domains that are retained by mature lymphoid cells but lost in terminally differentiated monocytes and erythroblasts. We demonstrate that inhibition of polycomb group members predicted to control large organized chromatin K27-modification domains influences lymphoid and myeloid fate decisions of primary neonatal hematopoietic progenitors in vitro. We further show that a majority of active enhancers appear in early progenitors, a subset of which are DNA hypermethylated and become hypomethylated and induced during terminal differentiation. Conclusion Primitive human hematopoietic cells display a unique repressive H3K27me3 signature that is retained by mature lymphoid cells but is lost in monocytes and erythroblasts. Intervention data implicate that control of this chromatin state change is a requisite part of the process whereby normal human hematopoietic progenitor cells make lymphoid and myeloid fate decisions.Medicine, Faculty ofScience, Faculty ofOther UBCMedical Genetics, Department ofMicrobiology and Immunology, Department ofReviewedFacultyResearche

Autophagy Regulation of Metabolism Is Required for CD8+ T Cell Anti-tumor Immunity

Summary: Autophagy is a cell survival process essential for the regulation of immune responses to infections. However, the role of T cell autophagy in anti-tumor immunity is less clear. Here, we demonstrate a cell-autonomous role for autophagy in the regulation of CD8+ T-cell-mediated control of tumors. Mice deficient for the essential autophagy genes Atg5, Atg14, or Atg16L1 display a dramatic impairment in the growth of syngeneic tumors. Moreover, T cells lacking Atg5 have a profound shift to an effector memory phenotype and produce greater amounts of interferon-γ (IFN-γ) and tumor necrosis factor α (TNF-α). Mechanistically, Atg5−/− CD8+ T cells exhibit enhanced glucose metabolism that results in alterations in histone methylation, increases in H3K4me3 density, and transcriptional upregulation of both metabolic and effector target genes. Nonetheless, glucose restriction is sufficient to suppress Atg5-dependent increases in effector function. Thus, autophagy-dependent changes in CD8+ T cell metabolism directly regulate anti-tumor immunity. : DeVorkin et al. show that loss of autophagy enhances CD8+ T-cell-mediated rejection of tumors. Mechanistically, suppression of autophagy shifts T cells to a glycolytic phenotype and causes a reduction in S-adenosylmethionine. As a consequence, autophagy-deficient T cells transcriptionally reprogram immune response genes to an effector memory state. Keywords: autophagy, CD8+ T cells, anti-tumor immunity, glycolysis, lactate, SAM, methylatio