Epigenetic regulators tet2 and polycomb repressive complex 2 (prc2) coordinate gene expression in myelodysplastic syndrome (mds)

Myelodysplastic syndrome (MDS) is a heterogeneous disorder that arises from somatic driver mutations that cause the expansion of mutant hematopoietic stem cells (HSCs). Acquisition of additional mutations can lead to transformation into Acute Myeloid Leukemia (AML). Epigenetic regulators including TET2 and DNMT3A are frequently mutated in MDS. Somatic loss of function TET2 mutations lead to HSC self-renewal that results in myeloproliferation, splenomegaly, and extramedullary hematopoiesis. We know TET2 plays an initial role in active DNA de-methylation, but the mechanism of how the disruption of this process can result in transformation to AML is still unknown. We hypothesize that loss of TET2 results in a gain in DNA methylation triggering an aberrant epigenetic cascade that dysregulates gene expression in stem and progenitor cells. We collaborated with the CAGE Core at St. Jude to develop TET2 knock out K562 cell lines to evaluate the effects of loss of TET2 on DNA methylation (WGBS) and transcription (RNA-Seq). We identified >5,000 regions that gain DNA methylation upon loss of TET2 that reside within intronic regions that are repressed in K562 cells. These gains in DNA methylation occur within genes that are up regulated upon loss of TET2. Taking these data together, we hypothesize that polycomb repressive complex 2 (PRC2) recruitment is blocked upon TET2 loss which results in gene activation. To test this, we conducted H3K27me3 CUT&RUN and identified a significant loss of H3K27me3 at up-regulated genes. Additionally, we evaluated gene expression changes in TET2-mutant AML samples and identified a conserved set of gene candidates that are putatively regulated by DNA methylation and PRC2 changes. These finding begin to unravel an epigenetic regulatory mechanism responsible for maintaining normal gene expression patterns in HSCs. Myelodysplastic syndrome (MDS) is a heterogeneous disorder that arises from somatic driver mutations that cause the expansion of mutant hematopoietic stem cells (HSCs). Acquisition of additional mutations can lead to transformation into Acute Myeloid Leukemia (AML). Epigenetic regulators including TET2 and DNMT3A are frequently mutated in MDS. Somatic loss of function TET2 mutations lead to HSC self-renewal that results in myeloproliferation, splenomegaly, and extramedullary hematopoiesis. We know TET2 plays an initial role in active DNA de-methylation, but the mechanism of how the disruption of this process can result in transformation to AML is still unknown. We hypothesize that loss of TET2 results in a gain in DNA methylation triggering an aberrant epigenetic cascade that dysregulates gene expression in stem and progenitor cells. We collaborated with the CAGE Core at St. Jude to develop TET2 knock out K562 cell lines to evaluate the effects of loss of TET2 on DNA methylation (WGBS) and transcription (RNA-Seq). We identified >5,000 regions that gain DNA methylation upon loss of TET2 that reside within intronic regions that are repressed in K562 cells. These gains in DNA methylation occur within genes that are up regulated upon loss of TET2. Taking these data together, we hypothesize that polycomb repressive complex 2 (PRC2) recruitment is blocked upon TET2 loss which results in gene activation. To test this, we conducted H3K27me3 CUT&RUN and identified a significant loss of H3K27me3 at up-regulated genes. Additionally, we evaluated gene expression changes in TET2-mutant AML samples and identified a conserved set of gene candidates that are putatively regulated by DNA methylation and PRC2 changes. These finding begin to unravel an epigenetic regulatory mechanism responsible for maintaining normal gene expression patterns in HSCs.