MOLECULAR GENETICS AND EPIGENETICS OF FRAGILE X SYNDROME

脆性 X 综合征的分子遗传学和表观遗传学

• 批准号: 2392269
• 负责人: CHARLES D LAIRD
• 金额: $ 26.33万
• 依托单位: FRED HUTCHINSON CANCER RESEARCH CENTER
• 依托单位国家: 美国
• 财政年份: 1995
• 资助国家: 美国
• 起止时间: 1995-04-01 至 1999-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/2392269
• 关键词: CpG islands; DNA replication; SDS polyacrylamide gel electrophoresis; animal tissue; chemical binding; cytogenetics; electrofocusing; endonuclease; family genetics; fragile X syndromes; gel electrophoresis; gene expression; gene mutation; genetic translation; genomic imprinting; human subject; hybrid cells; methylation; nucleic acid sequence; polymerase chain reaction; tissue /cell culture; western blottings

The triplet repeat diseases, currently seven in number, represent a new mutational class that has not previously been identified as a basis of genetic change in any of the "model" organisms. Fragile-X syndrome, the most common form of inherited mental retardation, was the first of these diseases for which publication demonstrated that the expansion of a triplet repeat was correlated with the disease state. Fragile-X syndrome also exhibits another unusual phenomenon in which gene inactivation occurs in a parent-specific manner: mutant alleles of the FMR1 gene are often inactivated by hypermethylation of a 5' CpG island when it is inherited from the mother but not from the father. The inactive state of the mutant FMR1 gene is described here as "imprinted" because of this pattern of inheritance. The long-term objectives of the proposed research are to understand genetic and epigenetic principles of the fragile-X syndrome. Specific questions concern the molecular basis of the instability of the CGG repeat within the candidate gene for the fragile-X syndrome, FMR1; the molecular nature of the imprinted or inactive state of the fragile-X mutation; whether or not the inactive state is reversible; the relationship between the cytogenetic expression of the fragile site at Xq27.3 (FRAXA), the expanded, hypermethylated CGG repeat, and delayed replication FMR1. The research design and methods for achieving these goals involve a combination of genetic and molecular approaches: molecular tests will assess the timing of DNA replication; methylation patterns at the fragile- X site will be characterized by restriction endonuclease assays and direct genomic sequencing; 5-azacytidine treatment of cell cultures will be used to assess the reversibility of the imprinted state. The health relatedness of this project concerns the genetic, epigenetic, and molecular basis of the fragile-X syndrome. The principles learned from this study also may be useful in understanding other diseases that involve expansion of triplet repeats: Kennedy disease, myotonic dystrophy, Huntington disease, spinocerebellar ataxia type I, dentatorubral- pallidoluysian atrophy, and FRAXE-related mental retardation. There is also potential relevance to disorders that involve either abnormal or normal genomic imprinting, such as Prader-Willi and Angelman syndromes, rhabdomyosarcoma, Beckwith-Wiedemann syndrome, and Wilms tumor.

三重重复疾病，目前有七种，代表了一种新的 一种以前没有被确定为基础的突变类型， 任何“模型”生物体的基因变化。脆性X综合征 最常见的遗传性智力迟钝，是第一个。 这些疾病的出版物表明， 三联体重复序列与疾病状态相关。脆性x染色体综合征 也显示出另一种不寻常的现象， 在父母特异性的方式：突变等位基因的FMR 1基因往往是 当它是遗传性的时，通过5' CpG岛的超甲基化而失活 但不是来自父亲突变体的非活动状态 FMR 1基因在这里被描述为“印记”，因为这种模式的 传承 拟议研究的长期目标是了解 脆性X综合征的遗传和表观遗传原理。具体 问题涉及CGG重复序列不稳定的分子基础 在脆性X综合征的候选基因FMR 1中， 脆性X突变的印记或非活性状态的性质; 非活动状态是否可逆; 脆性位点Xq27.3（FRAXA）的细胞遗传学表达， 扩增的、高甲基化的CGG重复序列和延迟复制的FMR 1。 实现这些目标的研究设计和方法涉及一个 基因和分子方法的结合：分子测试将 评估DNA复制的时间;在脆弱- X位点将通过限制性内切酶测定和直接测序来表征。 基因组测序;将使用5-氮杂胞苷处理细胞培养物 来评估印记状态的可逆性 该项目的健康相关性涉及遗传，表观遗传， 以及脆性X综合征的分子基础这些原则是从 这项研究也可能有助于了解其他疾病， 三联体重复扩增：肯尼迪病，强直性肌营养不良， 亨廷顿病，脊髓小脑性共济失调I型，齿状核红核- 苍白球路易体萎缩和FRAXE相关的精神发育迟滞。有 也可能与涉及异常或 正常的基因组印记，如Prader-Willi和Angelman综合征， 横纹肌肉瘤、贝-威二氏综合征和肾母细胞瘤。