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: 2193215
• 负责人: CHARLES D LAIRD
• 金额: $ 24.7万
• 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 1998-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/2193215
• 关键词: 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.

三联重复疾病目前有七种，代表了一种新的疾病 以前未被确定为基础的突变类别 任何“模型”生物体的遗传变化。脆性 X 综合征 最常见的遗传性智力低下形式是第一种 出版物表明疾病的扩大 三联体重复与疾病状态相关。脆性X综合征 还表现出另一种不寻常的现象，即发生基因失活 以亲本特异性方式：FMR1 基因的突变等位基因通常是 遗传时因 5' CpG 岛的超甲基化而失活 来自母亲，但不是来自父亲。突变体的非活性状态 FMR1 基因在这里被描述为“印记”，因为这种模式 遗产。 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。具体的 问题涉及 CGG 重复序列不稳定性的分子基础 脆性 X 综合征的候选基因 FMR1；分子 脆性 X 突变的印记或失活状态的性质； 非活动状态是否可逆；之间的关系 Xq27.3（FRAXA）脆弱位点的细胞遗传学表达， 扩增的、高甲基化的 CGG 重复序列和延迟复制的 FMR1。 实现这些目标的研究设计和方法涉及 遗传和分子方法的结合：分子测试将 评估 DNA 复制的时间；脆弱区域的甲基化模式 X 位点将通过限制性核酸内切酶测定进行表征并直接 基因组测序；将使用 5-氮杂胞苷处理细胞培养物 评估印迹状态的可逆性。 该项目的健康相关性涉及遗传、表观遗传、 和脆性X综合征的分子基础。从中学到的原理 这项研究也可能有助于了解其他涉及疾病的疾病 三联体重复的扩展：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、齿状红 - 苍白球路易体萎缩和 FRAXE 相关的智力低下。有 也与涉及异常或异常的疾病有潜在的相关性。 正常的基因组印记，例如普瑞德-威利综合征和天使综合征， 横纹肌肉瘤、贝克威斯-维德曼综合征和肾母细胞瘤。