The mechanistic basis for constitutional MLH1 methylation (epimutation)

组成性 MLH1 甲基化（表突变）的机制基础

• 批准号: 10020340
• 负责人: Megan P Hitchins
• 金额: $ 46.46万
• 依托单位: CEDARS-SINAI MEDICAL CENTER
• 依托单位国家: 美国
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-09-18 至 2023-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10020340
• 关键词: Address; Affect; Alleles; Blood; Cancer Etiology; Chromium; Chromosome 3; Chromosomes; Clinical; Clinical Management; Collection; Complex; Constitutional; DNA; DNA Sequence Alteration; Data; Defect; Detection; Development; Disease; Epigenetic Process; Etiology; Event; Family; Family Cancer History; Family Study; Family member; First Degree Relative; Gene Silencing; Generations; Genes; Genetic; Genetic Counseling; Genome; Germ Cells; Germ-Line Mutation; Goals; Haplotypes; Hereditary Malignant Neoplasm; Hereditary Nonpolyposis Colorectal Neoplasms; Heritability; Human; Inheritance Patterns; Inherited; Leukocytes; Light; Link; MLH1 gene; Malignant Neoplasms; Medical Genetics; Methylation; Microsatellite Repeats; Mismatch Repair; Modeling; Modification; Molecular; Mosaicism; Mutation; Normal tissue morphology; Nucleotides; Parents; Patients; Pattern; Research Personnel; Resources; Retrotransposon; Risk; Role; Sampling; Secondary to; Single Parent; Somatic Cell; Son; Structure; Transcriptional Regulation; Validation; Variant; Work; base; cancer type; epigenome; gene repair; genetic analysis; genetic variant; genome sequencing; genome wide methylation; improved; indexing; insight; intergenerational; methylation testing; novel; offspring; proband; promoter; reconstruction; segregation; transmission process; whole genome

Project Summary Lynch syndrome (LS), the most common hereditary cancer condition, is usually caused by a heritable genetic mutation affecting one of the DNA mismatch repair genes, most frequently MLH1, located on chromosome 3. So-called “MLH1 epimutation” is an alternative cause for LS. MLH1 epimutations are characterized by methylation of a single copy of the MLH1 promoter, accompanied by loss of gene activity, throughout normal tissues. This predisposes carriers to the development of LS-type cancers. Patients are identified by the detection of “constitutional” MLH1 methylation in DNA from blood or any other normal tissue. Studies of the family members of cases with an MLH1 epimutation have revealed distinct patterns of inheritance and hence differing risks of passing the epimutation from parent to offspring, if at all. Therefore, MLH1 epimutations provide a unique opportunity in humans for studying how epigenetic alterations arise and thereby cause disease, and also how epigenetic alterations are transmitted from one generation to the next in some families, but not in others. Dr. Hitchins, the principle investigator of this study, has assembled a unique collection of families with an MLH1 epimutation as the cause for cancer, and has established the inheritance patterns of the epimutation in each family, through her work in this field over the past 13 years. The goals of this study are to determine the mechanisms that underlie MLH1 epimutation by undertaking an in-depth study of the genomes and epigenomes of the patients and their families. In Aim 1, we will use state of the art “linked-read whole genome sequencing” to sequence the entire genome of selected patients and family members to determine if various types of genetic mutations on chromosome 3, or other chromosomes, underlie the onset on MLH1 epimutations. In Aim 2, we will determine if MLH1 is the only gene that is subject to erroneous constitutional methylation, or if other genes are simultaneously methylated. This would provide insights into whether epimutations arise because of a generalized epigenetic perturbation, or a focal mechanism affecting MLH1 alone. In Aim 3, we will validate any genetic or epigenetic alterations identified and determine their segregation patterns in families. We will also perform functional analyses of genetic variants identified previously and in Aim 1. Collectively, these studies will provide evidence for a causal link between genetic alterations identified and the MLH1 epimutation, and enable us to predict the likelihood of inheritance between generations. Finally, we will study patient white blood cells induced into a pluripotent state to model the epigenetic reprogramming events that occur at MLH1 in these patients. This will shed light on why some epimutations are inherited and others not. If successful, this study will enable us to improve the clinical management and genetic counselling of families with a cancer-predisposing MLH1 epimutation. More broadly, this study will provide significant new insights into the interaction between disease-causing genetic and epigenetic states, as well how altered epigenetic states may are passed from one generation to the next, or erased between generations.

项目摘要 Lynch综合征（LS）是最常见的遗传性癌症，通常由遗传性基因引起。 影响DNA错配修复基因之一的突变，最常见的是位于3号染色体上的MLH1。 所谓的“MLH1表型突变”是LS的另一个原因。MLH1表突变的特征在于： 在整个正常过程中，MLH1启动子的单拷贝甲基化，伴随着基因活性的丧失， 组织中这使携带者易于发展LS型癌症。患者由 检测来自血液或任何其他正常组织的DNA中的“组成性”MLH1甲基化。的研究 MLH1表型突变病例的家庭成员揭示了不同的遗传模式， 将表观突变从亲本传递给后代的风险不同，如果有的话。因此，MLH1表型突变 提供了一个独特的机会，在人类研究如何表观遗传改变出现，从而导致 疾病，以及表观遗传改变如何在一些家庭中从一代传递到下一代， 但在其他方面则不然。希钦斯博士，这项研究的主要研究者，已经收集了一个独特的收集， MLH1表型突变的家族是癌症的原因，并建立了MLH1表型突变的遗传模式。 通过她过去13年来在这一领域的工作，每个家庭都发生了突变。本研究的目的是 通过对基因组进行深入研究，确定MLH1表位突变的机制 和患者及其家属的表观基因组。在目标1中，我们将使用最先进的“链接阅读整体 基因组测序”对选定的患者和家庭成员的整个基因组进行测序，以确定是否 3号染色体或其他染色体上的各种类型的基因突变是MLH1发病的基础 表型突变在目标2中，我们将确定MLH1是否是唯一的基因，这是受到错误的宪法， 甲基化，或者如果其他基因同时甲基化。这将提供有关是否 表观突变的出现是由于广义的表观遗传扰动，或影响MLH1的焦点机制 一个人在目标3中，我们将验证鉴定的任何遗传或表观遗传改变并确定其分离 家庭模式。我们还将对以前和将来发现的遗传变异进行功能分析。 目标1。总的来说，这些研究将提供证据，证明基因改变之间的因果关系， 和MLH1表型突变，并使我们能够预测世代之间遗传的可能性。最后， 我们将研究患者的白色血细胞诱导成多能状态，以模拟表观遗传重编程。 这些患者在MLH1时发生的事件。这将阐明为什么一些表型突变是遗传的， 其他人没有。如果成功，这项研究将使我们能够改善临床管理和遗传咨询 癌症易感性MLH1表型突变的家庭。更广泛地说，这项研究将提供重要的新的 深入了解致病遗传和表观遗传状态之间的相互作用，以及如何改变 表观遗传状态可以从一代传递到下一代，或者在两代之间被消除。