Functional role of genes and pathways in histone H3 mutated gliomas

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Histones are evolutionarily highly conserved and their epigenetic modification plays a key role in the differentiation of eukaryotic cells and brain development. In brain tumors, histone H3 mutations (K27M, G34R and G34V) have been described as driver mutations in a subgroup of malignant gliomas showing aggressive biological behavior and poor response to therapy. Histone H3 mutations have been shown to cause transcriptional dysregulation, but little is known on functionally relevant genes and signaling pathways. Within the proposed DFG project, we aim at identifying genes and pathways involved in the biology of histone H3-mutated gliomas, which are of functional and clinical relevance. In particular, we want to better understand (1) how overexpression of mutated histone H3 affects central nervous system development, (2) investigate which genes and signaling pathways are involved in the detrimental effects of histone H3 mutations and (3) examine the functional role and clinical relevance of these genes and signaling pathways in histone H3 mutated tumors. To this end, we have established a fly model to study the effect of ubiquitous and cell-type specific over-expression of human mutated histone H3.3. In this model, we will employ a dual approach. In an unbiased approach we will (1) perform Gal4-UAS modifier screens by crossing in 1099 different fly strains expressing siRNA constructs of genes expressed in the fly nervous system and study the effect of ubiquitous and cell-type specific knockdown on the phenotype caused by overexpression of mutated histone H3.3. In parallel, we will (2) study the functional role of genes found to be over-expressed functional role of fly orthologues of human genes over-expressed in K27M mutated gliomas in this model. Results will be further validated by studying the effect of pharmacological inhibition of identified pathways. Expression, functional role (histone trimethylation, proliferation, migration) and clinical relevance of identified genes and signaling pathways will be examined in human histone H3-mutated tumor cell lines as well as clinically well-annotated histone H3-mutated tumor specimens, respectively. The results of this project will contribute to a better understanding of genes and pathways involved in the biology of histone H3-mutated gliomas. In the long term, they are expected to aid better treatments of patients harboring histone H3-mutated gliomas.