Genetic and Environmental Factors in Deletion Disorders

缺失性疾病中的遗传和环境因素

基本信息

批准号：
6663670
负责人：
Robert D Nicholls
金额：
$ 29.17万
依托单位：
UNIVERSITY OF PENNSYLVANIA
依托单位国家：
美国
项目类别：
财政年份：
2001
资助国家：
美国
起止时间：
2001-09-01 至 2006-07-31
项目状态：
已结题

项目摘要

DESCRIPTION (Investigator's abstract): A genomic disorder occurs de novo in region-specific repeats. Prototypic of genomic disorders are Prader-Willi and Angelman syndromes (PWS and AS), which arise in -1/7,500 births from a 4 Mb deletion of chromosome 15q11-q13. Our recent studies have shown the presence of 2-5 copies of paralogous sequences (duplicons) at or near each of a distal and two proximal PWS/AS breakpoint hotspots. The duplicons are derived in large part from genomic duplications of a novel gene (HERC2), while the tight clustering of breakpoints suggests a specific recombination mechanism leads to these deletions. We hypothesize that these duplicated sequences are involved in inter- and intra-chromosomal misalignment and homologous recombination, and that transcription of the duplicons in germ cells facilitates the recombination process. Finally, paternal occupational exposure to hydrocarbons has been associated with PWS, and we have shown that UV, X-rays, hydrocarbons and other chemicals enhance recombination of a similar genomic duplication in mice. Therefore, both genetic and environmental factors appear to predispose to chromosomal deletion events in PWS and AS. We propose four Specific Aims to examine the molecular mechanisms, and role of genetic and environmental susceptibility, in chromosome 15q1 1-q13 rearrangements: Aim 1. To determine the structure (number, orientation, sequence, gene content, and population variation) of HERC2-duplicons at 15Q11 and 15q13 by molecular cytogenetic and sequence echnologies. Aim 2. To identify sequence-specific hotspot(s) for chromosome recombination, we will clone and sequence deletion breakpoints using two novel assays, one detecting aberrant HERC2-related transcripts, and sequencing / informatics. Aim 3. We will examine genetic susceptibility (effect of inter-repeat distance, transcription and number of repeat copies) to intra- and inter-chromosomal deletion using a HERC2-GFP duplication model, including hotspot sequences (Aim 2), with assessment of the male germ cell rearrangement frequency using flow cytometry to detect GFP-tagged recombinants. Aim 4. We will determine whether environmental factors enhance the frequency of germ line recombination within Hprt- and HERC2-duplication mouse models, and similarly will examine genetic susceptibility using Ku80 about and p53- mice deficient in recombination pathways. These studies will identify the structure, variation and molecular pathological mechanisms underlying rearrangement of complex duplicated sequences in the mammalian germ line. Identification of environmental risk factors for germ line chromosome deletions may allow prevention of pre-conceptional exposure in the human population.

描述（研究者摘要）：基因组疾病从头发生于区域特异性重复。基因组疾病的原型是 Prader-Willi 和 Angelman 综合征（PWS 和 AS），-1/7,500 的新生儿中会出现 4 Mb 的情况染色体 15q11-q13 缺失。我们最近的研究表明存在远端和远端各处或附近有 2-5 个旁系同源序列（双倍体）拷贝两个近端 PWS/AS 断点热点。双倍子来源于大部分来自新基因（HERC2）的基因组重复，而紧密的断点的聚集表明特定的重组机制导致这些删除。我们假设这些重复序列参与染色体间和染色体内错位和同源重组，以及生殖细胞中双倍子的转录促进了重组过程。最后，父亲因职业接触碳氢化合物已被与 PWS 相关，我们已经证明紫外线、X 射线、碳氢化合物和其他化学物质增强了小鼠中类似基因组重复的重组。因此，遗传和环境因素似乎都容易导致 PWS 和 AS 中的染色体缺失事件。我们提出四个具体目标检查分子机制以及遗传和环境的作用易感性，染色体 15q1 1-q13 重排：目标 1. 确定结构（数量、方向、序列、基因内容和群体通过分子细胞遗传学和 15Q11 和 15q13 处的 HERC2 双倍子的变异）序列技术。目标 2. 识别序列特异性热点染色体重组，我们将使用克隆和测序删除断点两种新颖的检测方法，一种检测异常的 HERC2 相关转录本，以及测序/信息学。目标3.我们将检查遗传易感性（效应重复间距离、转录和重复拷贝数）到内部以及使用 HERC2-GFP 复制模型的染色体间删除，包括热点序列（目标 2），评估雄性生殖细胞重排使用流式细胞仪检测带有 GFP 标签的重组体的频率。目标 4. 我们将确定环境因素是否会提高种系频率 Hprt 和 HERC2 复制小鼠模型中的重组，以及类似的将使用 Ku80 about 和 p53- 缺乏的小鼠检查遗传易感性重组途径。这些研究将确定结构、变异以及复杂重排的分子病理机制哺乳动物种系中的重复序列。鉴定生殖系染色体缺失的环境风险因素可能允许预防人群孕前暴露。