Genetic and Environmental Factors in Deletion Disorders

描述（研究者摘要）：一种基因组疾病， 区域特异性重复序列。基因组疾病的原型是Prader-Willi和 Angelman综合征（PWS和AS），发生在4 Mb的-1/7，500例新生儿中， 染色体15 q11-q13缺失。我们最近的研究表明 2-5旁系同源序列（复制子）的拷贝位于或靠近每个远端和 两个近端PWS/AS断点热点。这些复制子是大量衍生的。 部分来自新基因（HERC 2）的基因组复制，而紧密的 断裂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 过程最后，父亲职业暴露于碳氢化合物已被 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相似基因组复制的重组。 因此，遗传和环境因素似乎都倾向于 PWS和AS中的染色体缺失事件。我们提出四个具体目标， 研究分子机制，以及遗传和环境的作用 易感性，染色体15 q11-q13重排：目的1。以确定 结构（数量、方向、序列、基因内容和种群 通过分子细胞遗传学检测15 q11和15 q13处HERC 2-重复子的变异， 序列技术目标2.为了鉴定用于以下的序列特异性热点： 染色体重组，我们将克隆和序列缺失断点使用 两种新的检测方法，一种检测异常HERC 2相关转录物， 测序/信息学。目标3.我们将检查遗传易感性（影响 重复序列间的距离，转录和重复拷贝数）内， 和使用HERC 2-GFP复制模型的染色体间缺失，包括 热点序列（Aim 2），评估雄性生殖细胞重排 使用流式细胞术检测GFP标记的重组体的频率。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HERC 2-重复小鼠模型内的重组，并且类似地 将使用Ku 80和p53缺陷的小鼠来检查遗传易感性。 重组途径这些研究将确定结构，变异 以及复合物重排的分子病理机制 在哺乳动物生殖细胞系中复制的序列。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.