The role of ATRX and H3.3 mutations in pediatric glioblastoma

描述(申请人提供)：脑瘤是儿童癌症相关死亡的主要原因。多形性胶质母细胞瘤(GBM)是一种致命的脑癌，儿童和成人都会患上。被诊断为GBM的儿童面临着悲惨的结局。即使是积极的治疗策略也是无效的，因为只有不到20%的儿童能在确诊后存活三年以上。对儿科GBM的测序发现，编码依赖于ATP的染色质重塑酶ATRX的基因在p53和组蛋白变体H3.3(由H3F3A和H3F3B编码)中同时发生突变。在癌症中，ATRX突变导致ATRX表达或活性的丧失，并与基因组不稳定、端粒和着丝粒异常表型以及不良的临床预后有关。在组蛋白尾部区域发现H3.3突变，该区域受到广泛的共价修饰。突变体H3.3的强制表达最近被证明是以一种显性的方式诱导染色质甲基化的全球变化，然而这些突变的功能后果仍然鲜为人知。基于这些发现，我们将检验ATRX和H3.3突变协同作用导致表观遗传不稳定、着丝粒和端粒异常以及GBM肿瘤发生的总体假设。首先，我们将产生新的脑癌小鼠模型，以模拟患者ATRX和H3.3突变的影响，并将提供给科学界用于未来的研究，测试某些药物是否可以抑制肿瘤的生长 这些肿瘤。同时，我们将在机制水平上调查ATRX和H3.3突变的后果。使用尖端显微镜和测序技术，我们将分析迫使正常神经前体细胞具有ATRX和H3.3突变后DNA和染色质组织的变化。我们还将纯化ATRX以及H3.3的正常和突变形式，并研究这些因素如何共同作用，在试管中将DNA重组为染色质。我们希望通过这些研究获得对ATRX和H3.3在调节染色质组织中的功能的详细了解，将有助于为患有ATRX和H3.3突变的脑肿瘤患者开发个性化的治疗方法。

DESCRIPTION (provided by applicant): Brain tumors are the leading cause of cancer-related deaths in children. Glioblastoma multiforme (GBM) is a deadly form of brain cancer that strikes both children and adults. Children diagnosed with GBM face dismal outcomes. Even aggressive treatment strategies are ineffective, as less than 20% of children will survive more than three years post-diagnosis. Sequencing of pediatric GBM has identified concurrent mutations in the genes encoding an ATP-dependent chromatin remodeling enzyme called ATRX, in p53, and in the histone variant, H3.3 (encoded by H3F3A and H3F3B). In cancer, ATRX mutations result in a loss of ATRX expression or activity and correlate with genome instability, aberrant telomere and centromere phenotypes, and with poor clinical prognosis. H3.3 mutations are found in the histone tail region that is subject to extensive covalent modification. Forced expression of mutant H3.3 has been recently shown to act in a dominant manner to induce global changes in the methylation of chromatin, yet the functional consequences of these mutations are still poorly understood. Based on these findings, we will test the overall hypothesis that ATRX and H3.3 mutations act in a cooperative manner leading to epigenetic instability, centromere and telomere abnormalities, and GBM tumorigenesis. First, we will generate novel mouse models of brain cancer to mimic the effects of patient ATRX and H3.3 mutations, which will be made available to the scientific community for future studies testing whether certain drugs can inhibit the growth of these tumors. In parallel, we will investigate the consequences of ATRX and H3.3 mutations on a mechanistic level. Using cutting edge microscopy and sequencing techniques we will analyze changes in DNA and chromatin organization after forcing normal neural progenitor cells to have ATRX and H3.3 mutations. We will also purify ATRX and both normal and mutant forms of H3.3 and study how these factors might work together to re-organize DNA into chromatin in a test tube. We hope that the detailed understanding of the functions of ATRX and H3.3 in mediating chromatin organization gained from these studies will enable the development of personalized therapies for cancer patients suffering from brain tumors with ATRX and H3.3 mutations.