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Genome-wide maps of chromatin state in KMT2D Knockout and KMT2D WT melanoma in mice

ABSTRACT: Somatic mutations in various epigenetic regulators, including histone methyltransferases KMT2C and KMT2D, have emerged as important cancer-driving events. However, the mechanism of action and therapeutic vulnerability imparted by these mutations remain poorly understood. We identified KMT2D and 8 other epigenetic regulators as potential suppressors to melanoma initiation through an in vivo pooled epigenome-focused RNAi screen. Loss of KMT2D, which exhibits somatic mutations in human melanoma and other cancers, drastically enhanced melanoma progression in xenograft models and a BRAFV600E-driven genetically engineered mouse model of melanoma. Epigenome profiling of 6 histone marks and chromatin state alterations showed substantial reprogramming of H3K4me1- and H3K27ac-marked active enhancer states in KMT2D mutant tumors. Energy metabolic pathways such as glycolysis, OxPhos and TCA/electron transport showed high degree of deregulation which was confirmed with metabolic profiling. Pharmacological abrogation of glycolysis led to reduced proliferation and tumorigenesis preferentially in KMT2D mutant cells. Mechanistically, we find that enhancer loss at IGFBPs increases IGF signaling and downstream AKT phosphorylation that leads to upregulation of metabolic pathways rendering KMT2D mutant cells dependent on these energy metabolism pathways for their higher growth potential. Overall, we present evidence that KMT2D mutations promote tumorigenesis by reprogramming energy metabolism pathways through enhancer reprogramming.

ORGANISM(S): Mus musculus

PROVIDER: GSE116851 | GEO | 2020/11/16

REPOSITORIES: GEO

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Project description:Kabuki Syndrome (KS) is a multisystemic rare disorder, characterized by growth delay, distinctive facial features, intellectual disability, and rarely autism spectrum disorder. This condition is mostly caused by de novo mutations of KMT2D, encoding a catalytic subunit of the COMPASS complex involved in enhancer regulation. KMT2D catalyzes the deposition of histone-3-lysine-4 mono-methyl (H3K4Me1) that marks active and poised enhancers. To assess the impact of KMT2D mutations in the chromatin landscape of KS tissues, we have generated patient-derived induced pluripotent stem cells (iPSC), which we further differentiated into neural crest stem cells (NCSC), mesenchymal stem cells (MSC) and cortical neurons (iN). In addition, we further collected blood samples from 5 additional KS patients. To complete our disease modeling cohort we generated an isogenic KMT2D mutant line from human embryonic stem cells, which we differentiated into neural precursor and mature neurons. Micro-electrode-array (MEA)-based neural network analysis of KS iNs revealed an altered pattern of spontaneous network-bursts in a Kabuki-specific pattern. RNA-seq profiling was performed to relate this aberrant MEA pattern to transcriptional dysregulations, revealing that dysregulated genes were enriched for neuronal functions, such as ion channels, synapse activity, and electrophysiological activity. Here we show that KMT2D haploinsufficiency tends to heavily affect the transcriptome of cortical neurons and differentiated tissues while sparing multipotent states, suggesting that KMT2D has a most prevalent role in terminally differentiated cell and activate transcriptional circuitry unique to each cell type. Moreover, thorough profiling of H3K4Me1 unveiled the almost complete uncoupling between this chromatin mark and the regulatory effects of KMT2D on transcription, which is instead reflected by a defect of H3K27Ac. By integrating RNA-seq with ChIP-seq data we defined TEAD and REST as the master effectors of KMT2D haploinsufficiency. Also, we identified a subset of genes whose regulation is controlled by the balance between KMT2D and EZH2 dosage. Finally, we identified the bona fide direct targets of KMT2D in healthy and KS mature cortical neurons and TEAD2 as the main proxy of KMT2D dysregulation in KS. Overall, our study provides the transcriptional and epigenomic characterization of patient-derived tissues as well as iPSCs and differentiated disease-relevant cell types, as well as the identification of KMT2D direct target in cortical neurons, together with the identification of a neuronal phenotype of the spontaneous electrical activity.

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Genome-wide maps of chromatin state in KMT2D Knockout and KMT2D WT melanoma in mice

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