MUTATION AND GENETIC ANALYSIS OF NEUROFIBROMATOSIS

1型神经纤维瘤病（NF 1）是人类最常见的肿瘤之一， 遗传性疾病，在所有族裔中的发病率为1/3000 组 主要特征包括色素沉着的真皮区域， 神经纤维瘤（良性肿瘤）源于神经鞘，骨 畸形和虹膜错构瘤。 大多数患者被诊断为 儿童或青春期，因为症状往往随着年龄的增长而进展， 荷尔蒙激增 医学目前只能提供标准治疗， 一些个别症状-无法治愈或治疗以延缓进展 存在. NF 1基因是位于染色体17上的约300 kb基因座， 被NF 1患者的体质突变所破坏。 它被认为 是一个肿瘤抑制基因，基于与损失相关的表型 的功能。 一个被广泛接受的假设表明， 细胞中两个NF 1等位基因的功能改变（另一个缺失） 体细胞突变的结果，“第二次打击”）导致表型。 该项目的长期目标是确定NF 1基因突变， 为了回答有关遗传学的具体问题， 障碍，并检查两次击中假设。 首先， 定义一组突变以按类型分类NF 1突变， 基因内的位置，因为目前很少有突变数据 列表. 其次，外显率的问题并不清楚--所有人都这样做吗 是否会出现症状渗透率将是 研究通过识别NF 1基因突变中的一系列“新突变”， 家庭以及传播不清楚的家庭 常染色体显性遗传（如多个受影响的儿童从正常 父母，或“跳过”的一代）。 DNA和RNA将通过 几种用于检测突变的分子遗传技术， 包括脉冲场电泳和基于PCR的 单个外显子和cDNA片段。 这项研究还可以提供一个 更好地估计“新突变”的真实发生率。“在 此外，最近两项使用连锁标记的研究表明， 高比例的NF 1突变出现在父系生殖系中， 与年龄无关。 中确定的每个新突变的亲本来源 本研究将使用编码区内的多态性进行分析， NF 1基因本身。任何母亲产生的突变都将是 进一步研究的重点，调查是否有任何 这些特征将它们与父系衍生的突变区分开来。 为了研究“两次打击”假设，将进行突变分析。 对血液和几个身体分离的DNA进行了分析， 神经纤维瘤。 发现相同的 在每个肿瘤中存在不同的“第二”突变 可以验证肿瘤抑制假说 这些数据 研究将大大有助于研究的功能， NF 1基因和突变数据库，这将是有用的 DNA诊断的发展和NF 1的进一步研究。

Neurofibromatosis type 1 (NF1) is among the most prevalent of human genetic diseases, with a frequency of 1/3000 individuals in all ethnic groups. The major features include pigmented dermal regions, neurofibromas (benign tumors) arising from nerve sheaths, bone deformities, and hamartomata of the iris. Most patients are diagnosed in childhood or adolescence, as the symptoms tend to progress with age and hormonal surges. Medicine currently can only offer standard treatment of some individual symptoms - no cure or treatment to retard progression exists. The NF1 gene is an approximately 300 kb locus on chromosome 17 which is disrupted by constitutional mutations in NF1 patients. It is thought to be a tumor suppressor gene, based on phenotype being associated with loss of function. A widely accepted hypothesis suggests that loss or alteration of function from both NF l alleles in a cell (the other loss the result of somatic mutation, a "second hit") results in the phenotype. The long-term goal of this project is to identify NF1 gene mutations in order to answer specific questions regarding the genetics of the disorder, and to examine the two-hit hypothesis. First, it is important to define a set of mutations to categorize NF1 mutations by type and location within the gene, since very little mutational data currently lists. Secondly, the issue of penetrance is not clear-do all individuals with constitutional NF1 mutations express symptoms? Penetrance will be studied by identifying NF1 gene mutations in a series of "new mutation" families, as well as in families in which the transmission is not clearly autosomal dominant (such as multiple affected children from normal parents, or "skipped" generations). DNA and RNA will be analyzed by several molecular genetic techniques designed to detect mutations, including pulsed field electrophoresis, and PCR-based analysis of individual exons and cDNA fragments. This research may also provide a better estimate of the true rate of occurrence of "new mutation." In addition, two recent studies using linked markers suggest that a very high proportion of NF1 mutations arise in the paternal germline, unrelated to age. Parental origin of each new mutation identified in this study will be analyzed using polymorphisms within the coding regions of the NF1 gene itself. Any maternally-arising mutations will be the focus of further study, to investigate whether there are any characteristics that set them apart from paternally-derived mutations. To investigate the "two-hit" hypothesis, mutational analysis will be performed on the DNA from blood and from several physically separate neurofibromas from the each of several patients. Discovery of the same constitutional mutation yet different "second" mutations in each tumor would verify the tumor suppressor hypothesis. The data from these studies will significantly contribute to research into the function of the NF1 gene and the mutation data base, which will be useful for development of DNA diagnosis and further NF1 research.