Heterozygous KMT2D Loss and Medulloblastoma

杂合 KMT2D 缺失和髓母细胞瘤

• 批准号: 10680489
• 负责人: Min Gyu Lee
• 金额: $ 43.16万
• 依托单位: UNIVERSITY OF TX MD ANDERSON CAN CTR
• 依托单位国家: 美国
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-08-09 至 2027-07-31
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10680489
• 关键词: AKT1 gene; Acceleration; Alleles; Apoptosis; Brain; Brain region; Cell Proliferation; Cells; Cerebellum; ChIP-seq; Characteristics; DNA Sequence; DNA Sequence Alteration; Data; Development; Enhancers; Epigenetic Process; Equilibrium; Future; G Protein-Coupled Receptor Signaling; Gene Expression; Gene Expression Regulation; Genes; Genetic Transcription; Genetically Engineered Mouse; Goals; Heritability; Heterozygote; Histone H3; Histones; Human; Loss of Heterozygosity; LoxP-flanked allele; Lysine; MLL2 gene; Malignant - descriptor; Mathematics; Mediating; Methylation; Methyltransferase; Modeling; Molecular; Motor; Mus; Mutate; Mutation; NCOR2 gene; Neuronal Differentiation; Neurons; Nucleic Acid Regulatory Sequences; Oncogenic; Oncoproteins; Oxidation-Reduction; PTCH gene; Pathogenesis; Pathogenicity; Pathway interactions; Patients; Pattern; Pediatric Neoplasm; Phenotype; Phosphotransferases; Post-Translational Protein Processing; Primary Brain Neoplasms; Process; Regulator Genes; Reporting; Repression; Role; SHH gene; Signal Pathway; Signal Transduction; Testing; Therapeutic; Therapeutic Intervention; Transcription Coactivator; Transcriptional Regulation; Tretinoin; Tumor Promotion; Tumor Suppressor Genes; Tumor Suppressor Proteins; cancer type; clinically relevant; design; epigenetic regulation; epigenomics; gene interaction; genome-wide; granule cell; histone demethylase; histone methylation; histone methyltransferase; in vivo; insight; medulloblastoma; motor control; mouse model; neoplastic cell; nestin protein; programs; promoter; rational design; side effect; spatiotemporal; stem cells; tumor; tumorigenesis

PROJECT SUMMARY Medulloblastoma (MB) is the most common malignant primary brain tumor in children. MB is frequently induced by the alterations of cellular signaling pathways, such as sonic hedgehog and wingless pathways, which have been extensively characterized. Nevertheless, current treatment of MB causes severe life-long side effects and fails to cure many patients. Thus, there is an unmet need for a new mechanistic understanding that would be helpful for designing a mechanism-based approach for MB treatment. Epigenetic aberrations, which are heritable aberrations in gene expression or cellular phenotypes without accompanying changes in DNA sequences, are a major factor for tumorigenesis. Epigenetic modifiers often harbor DNA alterations, such as mutations and deletions, in human MB. However, the roles of epigenetic modifiers in MB development remain largely unknown. Histone lysine methylation, a type of histone posttranslational modification, is a hallmark of epigenetic and transcriptional regulation of gene expression and is reversibly modified by histone methyltransferases and demethylases. Of histone lysine methylation, methylations at histone H3 lysine 4 (H3K4) are key gene-activating epigenomic marks. For example, monomethyl H3K4 is a mark for enhancers, which activate genes by interacting with gene promoters. In addition, trimethyl H3K4 occupies as much as 75 % of all human gene-regulatory regions, and broad trimethyl H3K4 is a gene-activating signature that denotes tumor suppressor and cell identity genes. We have previously reported that the H3K4 methyltransferase KMT2D (also called MLL4, ALR, and MLL2; a transcriptional coactivator) is required for retinoic acid-induced neuronal differentiation of human neuron-lineage NT2/D1 stem cells. Notably, our other study showed that homozygous loss of Kmt2d in the mouse brain developed spontaneous MB in the cerebellum, a brain region that controls motor coordination and balance. Strikingly, our additional results showed that heterozygous loss (single-allelic) of Kmt2d highly promoted MB. Based on these compelling findings, our long-term goal is to define the oncogenic role of heterozygous loss of Kmt2d in MB pathogenesis. Our central hypothesis is that heterozygous loss of Kmt2d causes epigenomic alterations to downregulate tumor suppressor genes and thereby promotes MB. Here, we propose to study to 1) characterize the MB-promoting effect of heterozygous Kmt2d loss using genetically engineered mouse models; 2) define the molecular mechanism by which heterozygous Kmt2d loss promotes MB; and 3) determine how heterozygous Kmt2d loss causes epigenomic alterations. Because KMT2D is one of the most frequently mutated genes in MB and a majority of KMT2D mutations in MB are heterozygous and truncations, our proposed studies are significant and clinically relevant. In addition, our studies using genetically engineered mouse models will define an in vivo MB-promoting role for heterozygous Kmt2d loss. Furthermore, our results will uncover the previously unappreciated epigenetic mechanism underlying MB pathogenesis and provide valuable information for the rational design of a therapeutic approach for MB treatment.

项目摘要 髓母细胞瘤（MB）是儿童最常见的恶性原发性脑肿瘤。MB经常被诱发 通过改变细胞信号通路，如音刺猬和无翼通路， 被广泛地描述。尽管如此，目前的MB治疗会导致严重的终生副作用， 不能治愈很多病人。因此，需要一种新的机械理解， 有助于设计一种基于机制的MB治疗方法。表观遗传畸变， 基因表达或细胞表型的畸变，而不伴随DNA序列的变化，是一种 肿瘤发生的主要因素。表观遗传修饰剂通常含有DNA改变，如突变和 缺失，在人MB中。然而，表观遗传修饰剂在MB发展中的作用在很大程度上仍然未知。 组蛋白赖氨酸甲基化是组蛋白翻译后修饰的一种类型，是表观遗传学的标志， 基因表达的转录调控，并被组蛋白甲基转移酶可逆地修饰， 脱甲基酶在组蛋白赖氨酸甲基化中，组蛋白H3赖氨酸4（H3 K4）的甲基化是基因激活的关键。 表观基因标记例如，单甲基H3 K4是增强子的标记，增强子通过相互作用激活基因， 基因启动子。此外，三甲基H3 K4占据了所有人类基因调控区的75%， 而广泛的三甲基H3 K4是一个基因激活标记，它表示肿瘤抑制基因和细胞身份基因。 我们以前曾报道过H3 K4甲基转移酶KMT 2D（也称为MLL 4，ALR和MLL 2; 转录辅激活因子）是维甲酸诱导的人类神经元谱系神经元分化所必需的 NT 2/D1干细胞值得注意的是，我们的另一项研究表明，小鼠大脑中Kmt 2d的纯合缺失 小脑是控制运动协调和平衡的大脑区域。 引人注目的是，我们的额外结果表明，Kmt 2d的杂合丢失（单等位基因）高度促进MB。 基于这些令人信服的发现，我们的长期目标是确定杂合性缺失的致癌作用。 MB发病机制中的Kmt 2d。我们的中心假设是Kmt 2d的杂合缺失导致表观基因组 改变下调肿瘤抑制基因，从而促进MB。在这里，我们建议研究1） 使用基因工程小鼠模型表征杂合Kmt 2d缺失的MB促进作用; 2)定义杂合Kmt 2d缺失促进MB的分子机制;以及3）确定如何 杂合Kmt 2d缺失导致表观基因组改变。因为KMT 2D是一种最常见的突变， MB中的基因和MB中的大多数KMT 2D突变是杂合和截短的，我们提出的研究 具有临床意义。此外，我们使用基因工程小鼠模型的研究将 定义了杂合子Kmt 2d缺失的体内MB促进作用。此外，我们的研究结果将揭示 MB发病机制的表观遗传机制以前未被认识，并提供有价值的信息 用于MB治疗的治疗方法的合理设计。

项目成果

Heterozygous Kmt2d loss diminishes enhancers to render medulloblastoma cells vulnerable to combinatory inhibition of lysine demethylation and oxidative phosphorylation.

杂合 Kmt2d 缺失会减少增强子，使髓母细胞瘤细胞容易受到赖氨酸去甲基化和氧化磷酸化的联合抑制。

• DOI: 10.1101/2023.10.29.564587
• 发表时间: 2023
• 期刊: bioRxiv : the preprint server for biology
• 作者: Dhar,ShilpaS;Brown,Calena;Rizvi,Ali;Reed,Lauren;Kotla,Sivareddy;Zod,Constantin;Abraham,Janak;Abe,Jun-Ichi;Rajaram,Veena;Chen,Kaifu;Lee,MinGyu
• 通讯作者: Lee,MinGyu