MAPPING AND CLONING OF THE BLOOM'S SYNDROME LOCUS

Bloom综合征（BS）是一种常染色体隐性遗传疾病， 临床上表现为生长缺陷、免疫缺陷、生育能力下降， 一个巨大的易患癌症的各种类型， 网站. 尽管该基因被认为以某种核方式参与 随着基因组稳定性的维持，BS中的主要缺陷没有 被识别。 这项工作的目的是绘制和克隆 布鲁姆综合征基因座 这一目标将由 遵循计划。 1.利用连锁分析法将BLM基因定位在第15号染色体上 使用血缘关系绘图。 2.分离高度多态性的DNA标记，从由 链接（BLM区域）通过克隆DNA片段从辐射减少 杂种和显微切割的染色体。 3.通过以下方式细化这些标记在BLM区域中的地图位置： 血缘作图、连锁不平衡作图和长程 限制性酶切作图 4.使用YAC（酵母人工染色体）分离BLM区域 由最接近BLM的标记物鉴定，如3. 5.鉴定BLM的候选者，采用DNA介导的转化， 测试它们纠正BS细胞的高SCE表型的能力。 是 检测的是（a）来自完整YAC的DNA和（B）使用YAC鉴定的cDNA 作为杂交探针。 6.通过鉴定突变来确认候选基因。 Bloom综合征患者BLM基因座的分子水平。 目标的实现将提供关于 DNA复制和修复的关键方面。 这些知识将导致 了解野生型BLM基因的活性， 突变的BLM基因座的缺陷基因产物， 基因参与临床表型。 随着目前的进步 在人类遗传学领域的“染色体断裂综合征” 作为一个群体，似乎与DNA复制和修复有关， 哪个BS是原型-知识的总和可能会产生一个 综合和及时完整地了解这一复杂的过程， 从广义上讲，体细胞维持遗传稳定性的方式。

Bloom's syndrome (BS) is an autosomal recessive disorder characterized clinically by growth deficiency, immunodeficiency, reduced fertility, and an enormous predisposition to cancer of a wide variety of types and sites. Although the gene is believed to be involved in some nuclear way with maintenance of genomic stability, the primary defect in BS has not been identified. The purpose of the work proposed is to map and clone the Bloom's syndrome locus, BLM. this goal will be accomplished by the following plan. 1.Sub-localize the BLM locus on chromosome No. 15 by linkage analysis using consanguinity mapping. 2. Isolate highly polymorphic DNA markers from the region defined by the linkage (the BLM region) by cloning DNA segments from radiation-reduced hybrids and microdissected chromosomes. 3. Refine the map location of these markers in the BLM region by consanguinity mapping, linkage-disequilibrium mapping, and long-range restriction mapping. 4. Isolate the BLM region using YACs (yeast artificial chromosomes) identified by the markers closest to BLM as defined in 3. 5. Identify candidates for BLM, employing DNA-mediated transformation to test their ability to correct the high-SCE phenotype of BS cells. To be tested will be (a) DNA from whole YACs and (b) cDNA identified using YACs as hybridization probes. 6. Confirm a candidate gene by identification of mutation(s) at the molecular level in the BLM locus in individuals with Bloom's syndrome. The fulfillment of the goal will provide fundamental knowledge about a key aspect of DNA replication and repair. this knowledge will lead to understanding the activity of the wild type BLM gene, the role of the defective gene product from the mutated BLM locus, and how the mutated gene is involved in the clinical phenotype. With the current advances in the field of human genetics on the "chromosome-breakage syndromes" that as a group appear related to DNA replication and repair - and of which BS is the prototype - the sum total of knowledge may yield an integrated and in time complete view of this complex process, and in a broader sense, the way somatic cells maintain genetic stability.