PROJECT SUMMARY Gliomas represent 80% of the 26,000 newly diagnosed cases of malignant brain and central nervous system tumors in the United States each year and are among the most lethal and treatment-resistant human cancers. Hot-spot, mono-allelic, gain-of-function mutations in the isocitrate dehydrogenase genes IDH1 and IDH2 are present in more than 70% of certain subtypes of gliomas, thus representing the genetic hallmark of these malignant brain tumors. The ‘oncometabolite’ (R)-2-hydroxyglutarate [(R)-2HG], produced by IDH mutant enzymes, modulates the activities of certain 2-oxoglutarate (2OG) dependent DNA and histone demethylases, which subsequently promotes neural cell transformation. Accordingly, broad changes in histone and DNA methylation are strongly associated with IDH mutations in glioma. Despite these discoveries, the precise molecular mechanisms linking oncometabolite-dependent chromatin remodeling with gliomagenesis remain obscure. I propose to directly address this knowledge gap and test a new conceptual model to explain oncometabolite-driven tumorigenesis. In Aim 1, I will perform time-resolved single cell and bulk RNA-seq and ATAC-seq analyses of the molecular and cellular changes that occur during brain tumor initiation in a novel genetically engineered mouse (GEM) model of glioma to reveal key mechanisms of (R)-2HG dependent malignant transformation. In Aim 2, I will conduct integrative analyses of sequencing datasets from human glioma samples and murine glioma samples from our GEM models to discover functional targets of (R)-2HG in IDH mutant gliomas. In Aim 3, I will leverage novel mouse brain organoid models to investigate the impact of oncometabolite activity on neural cell specification during brain development. If successful, my work will provide a new conceptual framework for understanding the deterministic and stochastic functions of oncometabolite signaling to chromatin and their influence on cell fate. This advance would deepen our understanding of how metabolic alterations signal to chromatin in cancer and other diseases. Furthermore, identifying the molecular processes that functionally link oncometabolites with brain tumor initiation may reveal new therapeutic targets to combat this disease.