Uncover the role of H3.3-G343R mutation in shaping the DNA damage response, anti-tumor immunity and mechanisms of resistance in glioma.

儿科高级别胶质瘤(PHGGs)是最具侵袭性的脑癌之一， 生存(MS)~18个月1，2.PHGG目前的护理标准，包括肿瘤切除 通过放疗和化疗，只会引起MS1-4的适度增加。有限的主要原因是 治疗结果是由PHGG的浸润性引起的肿瘤复发，以及 免疫抑制的肿瘤微环境(TME)。半球形PHGG的主要亚型之一 编码组蛋白H3F3A 4中的G34R/V替换，以及ATRX和TP53失活突变。 对在PHGG发病机制中起作用的分子途径的研究需要准确 概括PHGG显著特征并在大脑微环境中发展的小鼠模型 在一个免疫能力强的宿主中。我们实验室建立了具有免疫能力的基因工程PHGG小鼠模型 使用睡美人(SB)转座酶系统5，6。肿瘤中遇到的遗传损伤 PHGG亚型，即H3.3G34R与ATRX和TP53共表达。这个PHGG模型中的宿主 展示完整的免疫系统，从而能够对PHGG生物学的各个方面进行详细的机制研究 在体内，包括与TME免疫细胞的相互作用。我们的H3.3-G34R与H3.3-G34R的初步RNA-Seq数据 H3.3-Wt PHGG揭示了与DNA损伤反应(DDR)相关的基因本体(GO)的下调 在H3.3-G34R PHGG。我们还观察到与免疫激活相关的GOS上调 H3.3-G34R的“免疫反应调节”和“I型干扰素产生”等应答 PHGG模型。在此，我们建议确定H3.3-G34R的细胞和分子机制 调节小鼠和人H3.3G34R PHGG细胞对放射治疗和DDR抑制的反应 在活体内。我们旨在阐明H3.3-G34R在DNA修复过程中所起的作用，以响应DNA 损害性物质，以及TME免疫细胞的重新编程。我们建议检验假设H3.3G34R 重塑表观遗传格局，导致染色质状态变化和转录变化。 这些改变导致DDR损伤并诱导基因组不稳定，进而导致cGAS-sting- 在H3.3G34R pHGG TME中通过途径介导的免疫系统激活。我们将评估 通过ATAC-SEQ检测染色质的状态，并确定染色质可及性降低是否会损害DNA修复 在G34R PHGG中。我们还将评估G34R PHGG中的基因组不稳定性是否调节免疫系统 通过cGAS-STING激活。我们还将在分子水平上定义表型多样化的肿瘤和 使用scRNA-seq在H3.3-G34R PHGG微环境中渗透免疫细胞簇；这将允许 美国试图揭示治疗耐药的机制。这些信息将使揭示基因构成成为可能- 针对H3.3-G34R PHGG的量身定制治疗方案，如细胞周期检查点或DDR抑制剂 配合放射治疗。

Pediatrichigh-grade gliomas (pHGGs) are one of the most aggressive forms of brain cancer, with a median survival (MS) of ~18 months 1,2. The current standard of care for pHGG, consisting of tumor resection followed by radiation and chemotherapy, elicits only a modest increase in MS 1-4. The main reasons for the limited therapeutic outcomes are tumor recurrence, caused by the infiltrative nature of pHGG, and the development of an immune-suppressive tumor microenvironment (TME). One of the main subtypes of hemispherical pHGG encodes for G34R/V substitutions in the histone H3F3A 4, along with ATRX and TP53 inactivating mutations. The investigation of the molecular pathways which play a role in the pathogenesis of pHGG requires accurate mouse models which recapitulate the salient features of pHGG and develop within the brain's microenvironment in an immune-competent host. Our lab created genetically engineered immune competent pHGG mouse models employing the Sleeping Beauty (SB) transposase system 5,6. Tumors harbor genetic lesions encountered in a subtype of pHGG, i.e., H3.3G34R co-expressed with ATRX and TP53 knock down. The host in this pHGG model exhibits an intact immune system, thus enabling detailed mechanistic studies on all aspects of pHGG biology in vivo, including interactions with the TME immune cells. Our preliminary RNA-Seq data on H3.3-G34R versus H3.3-Wt pHGG revealed downregulation of gene ontologies (GO) related to DNA Damage Response (DDR) in H3.3-G34R pHGG. We also observed upregulation of GOs related to the activation of the immune response, such as “Regulation of Immune Response” and “Type I Interferon Production”, in the H3.3-G34R pHGG model. Herein we propose to determine the cellular andmolecular mechanisms by which H3.3-G34R regulates the response to radiotherapy and DDR inhibition in mouse and human H3.3G34R pHGG cells in vitro and in vivo. We aim to elucidate the role played by H3.3-G34R in DNA repair processes, responseto DNA damaging agents, and in TME immune cells' reprogramming. We propose to test the hypothesis that H3.3G34R reshapes the epigenetic landscape, resulting in alterations in chromatin states and transcriptional changes. These alterations cause DDR impairment and induce genomic instability, which in turn leads to cGAS-STING- Pathway-mediated activation of the immune system within the H3.3G34R pHGG TME. We will assess chromatin states by ATAC-seq, and establish whether reduced chromatin accessibility impairs DNA repair in G34R pHGG. We will also evaluate whether genomic instability in G34R pHGG mediates the immune system activation via cGAS-STING. We will also define at the molecular level the phenotypically diverse tumor and infiltrating immune cell clusters within the H3.3-G34R pHGG microenvironment using scRNA-seq; this will allow us to uncover mechanisms of therapeutic resistance. This information, will enable uncovering genetic makeup- tailored therapeutic modalities for H3.3-G34R pHGG, such as cell cycle checkpoint or DDR inhibitors combined with radiotherapy.