Genetic and Environmental Factors in Deletion Disorders

描述(研究人员摘要)：一种新出现的基因组疾病 特定于区域的重复。基因组疾病的原型是Prader-Willi和 Angelman综合征(PWS和AS)，从4Mb出生的-1/7500新生儿中出现 染色体15q11-q13缺失。我们最近的研究表明， 2-5个平行序列(复制子)的副本，位于或靠近每个远端和 两个近端PWS/AS断点热点。这些复制品是用大号字体制作的。 部分来自一种新基因(HERC2)的基因组复制，而紧密的 断点的聚集表明了一种特定的重组机制导致 这些删除。我们假设这些重复的序列参与了 染色体间和染色体内错配和同源重组，以及 生殖细胞中复制子的转录促进了重组 进程。最后，父亲的职业接触碳氢化合物一直是 与PWS有关，我们已经证明了紫外线、X射线、碳氢化合物和其他 化学物质促进了小鼠体内类似基因组复制的重组。 因此，遗传和环境因素似乎都容易患上 PWS和AS中的染色体缺失事件。我们提出了四个具体目标 研究遗传和环境的分子机制和作用 易感性，在染色体15q1 1-q13重排：目的1.确定 结构(数量、方向、序列、基因含量和种群 15q11和15q13处HERC2重复序列变异)的分子细胞遗传学研究 序列技术。目的2.确定序列特异性热点(S) 染色体重组，我们将使用以下方法克隆和测序缺失断点 两种新的检测方法，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(影响 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缺失，包括 热点序列(目标2)，评估雄性生殖细胞重排 用流式细胞仪检测GFP标记的重组子的频率。目标4.我们 将决定环境因素是否会增加生殖系的频率 HPRT和HERC2复制小鼠模型中的重组，以及类似的 将使用Ku80约和p53基因缺陷的小鼠来检测遗传易感性 重组途径。这些研究将确定结构、变异 以及复合体重排的分子病理机制 哺乳动物生殖系中的重复序列。身份识别 生殖系染色体缺失的环境风险因素可能允许 预防人类人群中的孕前暴露。

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.