MECHANISMS AND CONSEQUENCES OF CHROMOSOMAL ABNORMALITIES

染色体异常的机制和后果

• 批准号: 6182421
• 负责人: David H. Ledbetter
• 金额: $ 31.3万
• 依托单位: UNIVERSITY OF CHICAGO
• 依托单位国家: 美国
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-07-01 至 2003-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6182421
• 关键词: artificial chromosomes; biochemical evolution; chromosome aberrations; chromosome deletion; chromosome inversion; chromosome translocation; clinical research; cytogenetics; disease /disorder etiology; fluorescent in situ hybridization; gene expression; gene rearrangement; genetic disorder; genetic disorder diagnosis; genetic mapping; genetic polymorphism; genetic recombination; human genetic material tag; human subject; molecular cloning; nucleic acid sequence; pulsed field gel electrophoresis; sequence tagged sites

DESCRIPTION (Adapted from the Investigator's Abstract): Structural chromosomal rearrangements are an important cause of human genetic disorders associated with mental retardation and other human developmental abnormalities. The etiology of recurring constitutional chromosomal rearrangements such as deletions, duplications, and marker chromosome formation is poorly understood. The investigators seek to address this problem by a complete genomic and molecular characterization of the chromosome region 15q11-q13, which is associated with an unusually high frequency and diversity of recurring rearrangements including one of the most frequent interstitial deletions observed in humans (1/10,000-1/20,000 births). Due to genomic imprinting, paternal deletions produce Prader-Willi syndrome (PWS) and maternal deletions produce the distinct genetic disorders, Angelman syndrome (AS). This region is also involved in 50 percent of all supernumerary marker chromosomes, and less frequently in intrachromosomal duplications, triplications, and jumping translocations. Evidence now suggests the presence of four hotspots for chromosome breakage in this region: two proximal to the PWS/AS region and two distal. Complete molecular characterization of this region may lead to a more basic understanding of the mechanism of chromosomal rearrangements. Specific goals of the project include the development of a high-resolution physical map of the approximately 8 Mb (reduced in size by 2 Mb) chromosome segment 15cen-15q14 using YAC and BAC contigs and STS content mapping. The goal is 1 STS/50 kb. The map will be anchored at the chromosome 15 centromere by YAC and BAC walking to close the current 1-2cM gap (previously a 12 cM gap). Progress will be monitored by interphase FISH analysis and by genetic mapping in ovarian teratomas with newly developed STRs and/or SNPs. The four recurring breakpoints (hotspots) will be cloned and sequenced to test the hypothesis that multiple copies of a large duplicated gene cluster (200-600 kb) mediate intrachromosomal and interchromosomal rearrangements. Features of these sequences, such as copy number, distribution, and orientation will be analyzed in normal controls and parents of children with de novo abnormalities to assess polymorphism or to identify any specific predisposing factors or genomic rearrangements. These sequences will also be studied among other great ape species for evidence of "evolutionary hotspots" for chromosomal rearrangement. The proposed orientation of the 4 duplicated clusters (direct-inverted-direct-direct) provides a framework for proposing and testing specific models to account for the diverse rearrangements observed in chromosome 15. An extensive patient collection will be developed representing each class of rearrangement (deletion, duplication, triplication, marker chromosome, jumping translocation) and each of the 4 breakpoint hotspots. For each patient and class of abnormality, the investigators will determine the content, parental origin, and specific breakpoint as well as determine whether the rearrangements are due to meiotic unequal crossing-over or intrachromosomal events. Specific breakpoints will be determined by FISH and pulse field gel electrophoresis, followed by sequencing in selected cases. Development of rapid and precise breakpoint specific assays and methylation assays may facilitate patient analysis and clinical diagnosis.

描述（改编自研究者的摘要）：结构 染色体重排是人类遗传疾病的重要原因 与智力低下和其他人类发育障碍有关 异常。 复发性体质性染色体异常的病因学 重排，例如缺失、重复和标记染色体 的形成知之甚少。 调查人员试图解决这个问题 通过完整的基因组和分子特征来解决问题 染色体区域 15q11-q13，与异常高的 经常性重排的频率和多样性，包括其中之一 在人类中观察到的最常见的间质缺失（1/10,000-1/20,000 出生）。 由于基因组印记，父系缺失会产生普瑞德-威利综合征 综合征（PWS）和母体缺失产生独特的遗传 疾病，天使综合征（AS）。 该地区还涉及 50 所有额外标记染色体的百分比，并且在 染色体内重复、三倍和跳跃易位。 现在的证据表明存在四个染色体断裂热点 在该区域中：两个靠近 PWS/AS 区域，两个靠近远端。 完全的 该区域的分子表征可能会导致更基本的 了解染色体重排的机制。 该项目的具体目标包括开发高分辨率 约 8 Mb（大小减少 2 Mb）染色体的物理图 使用 YAC 和 BAC 重叠群以及 STS 内容映射对 15cen-15q14 进行分段。 这 目标是 1 STS/50 kb。 该图谱将锚定在 15 号染色体上 着丝粒通过 YAC 和 BAC 行走来缩小当前 1-2cM 的间隙（之前 12 厘米间隙）。 将通过间期 FISH 分析和 使用新开发的 STR 和/或 SNP 进行卵巢畸胎瘤的遗传图谱分析。 四个重复出现的断点（热点）将被克隆并排序以 检验大型重复基因簇的多个副本的假设 (200-600 kb) 介导染色体内和染色体间重排。 这些序列的特征，例如拷贝数、分布和 将对正常对照组和患有此病的儿童的父母进行定向分析 从头异常来评估多态性或识别任何特定的 诱发因素或基因组重排。 这些序列也将 在其他类人猿物种中进行研究，以获取“进化论”的证据 染色体重排的热点”。建议的 4 个方向 重复集群（直接-反转-直接-直接）提供了一个框架 提出并测试特定模型以考虑多样化 在 15 号染色体中观察到的重排。广泛的患者收集 将开发代表每一类重排（删除， 复制、三倍、标记染色体、跳跃易位）和 4 个断点热点中的每一个。 对于每个患者和类别 异常情况，调查人员将确定其内容、父母出身、 和具体断点以及确定是否重新排列 由于减数分裂不平等交换或染色体内事件。 具体的 断点将通过 FISH 和脉冲场凝胶电泳确定， 然后对选定的病例进行测序。 开发快速精准 断点特异性检测和甲基化检测可能有利于患者 分析和临床诊断。