MOLECULAR GENETICS OF RETT SYNDROME

Rett综合征(RS)是一种神经退行性疾病，影响多达 每15,000只活着的雌性中就有1只。出生时正常，RS患者发展为 儿童早期严重的精神发育迟滞和运动障碍。这个 RS的临床过程和病理表明是一种原发的缺陷中断 中枢神经系统特定亚群的正常发育和维持 神经元。虽然大多数病例是零星的，但家族性病例表明 X连锁显性遗传和致死性或非致死性遗传病因学 在男性身上的表现。利用基因分型进行排异作图 家族性病例排除了大多数X染色体上推测的RS基因 染色体。识别引起RS的基因缺陷是很重要的 因为它将允许准确的诊断并提供关键的洞察力 RS的潜在治疗方法。 这项建议的主要目的是鉴定RS基因 使用四种基本方法来搜索突变。1) 代表性差异分析(RDA)，一种基于PCR的方法 唯一序列的分离将用于检测从头基因 RS患者的重排。突变检测的可能性将 通过利用来自多个无关的 有RS先证者的家庭。2)RS产生的可能性 将使用一组三核苷酸来探索三重重复序列的扩展 重复寡聚物法鉴定含三重重复的X连锁基因 序列。RDA产物和三联重复序列都将被使用 从RS患者中筛选DNA突变并分离 同源cdna或基因组克隆。3)X连锁的神经元基因将是 用Southern和SSC分析筛选突变。4)候选人X- 相关基因将被检查以寻找失活逃逸的证据。 表现为低甲基化和表达来自非活性S。 确定的潜在RS基因将被仔细检查RS的突变 对患者进行DNA测序，并检查其在 发育中的神经系统。了解基因的正常功能 哺乳动物中枢神经系统发育中的产物将阐明其分子 RS表型发病机制的研究。

Rett Syndrome (RS) is a neurodegenerative disorder which affects up to 1 in 15,000 liveborn females. Normal at birth, RS patients develop profound mental retardation and motor deficits in early childhood. The clinical course and pathology of RS suggest a primary defect interrupting the normal development and maintenance of specific subgroups of CNS neurons. While most cases are sporadic, familial occurrences suggest a genetic etiology with X-linked dominant inheritance and lethality or non- expression in males. Exclusion mapping using genotype analysis of familial cases excluded the putative RS gene from most of the X chromosome. Identification of the gene defect causing RS is important in that it will allow accurate diagnosis and give crucial insight toward potential treatment of RS. The primary aim of this proposal is the identification of the RS gene using four basic approaches to search for the mutation. 1) Representational Difference Analysis (RDA, a PCR-based method for isolation of unique sequences will be used to detect de novo gene rearrangements in RS patients. The likelihood of mutation detection will be maximized through the utilization of DNA from multiple unrelated families with RS probands. 2) The possibility that RS results from a triplet repeat expansion will be explored using a panel of trinucleotide repeat oligomers to identify X-linked genes containing triplet repeat sequences. Both RDA products and triplet repeat sequences will be used to screen DNA from RS patients for mutations as well as to isolate cognate cDNA or genomic clones. 3) X-linked neuronal genes will be screened for mutations by Southern and SSC Analysis. 4) Candidate X- linked genes will be examined for evidence of escape of inactivation manifest by hypomethylation and expression from the inactive S. Potential RS genes identified will be scrutinized for mutations in RS patients by DNA sequencing and examined for expression within the developing nervous system. Understanding the normal function of the gene product in development of the mammalian CNS will elucidate the molecular mechanisms underlying the pathogenesis of the RS phenotype.