不明原因智力低下儿童脆性X综合征的筛查和基因诊断

目的建立一种快速分析脆性X综合征智力低下基因1(Fragile X mental retardation gene 1,FMR-1)突变的方法,对不明原因智力低下儿童进行脆性X综合征的筛查和诊断。方法应用7-deza-dGTP的PCR法一次性扩增FMR-1基因的(CGG)n的重复区,检测CGGn的重复序列的大小判断FMR-1基因状态(正常、突变前、突变后),对脆性X综合征可疑患儿快速筛查。结果在101例不明原因的先天性智力低下惠儿中,我们发现脆性X综合征患儿13例(男性10例,女性3例)。结论采用7-deza-dGTP扩增GC富集区的PCR法可对高危患儿进行快速筛查,确定携带者和患者。     

先天性智力低下儿童脆性X综合征的分子流行病学调查

目的根据脆性X综合征的两个分子生物学标志,建立在先天性智力低下患儿中快速分析脆性X综合征智力低下基因1(Fragile X mental retardation gene 1,FMR1)突变的方法,对先天性智力低下儿童进行脆性X综合征的大面积筛查和诊断,调查智力低下儿童中脆性X综合征的发病率。方法应用复式PCR方法检测FMR1基因的(CGG)n重复区CGG重复序列的大小,判断FMR1基因状态(正常、前突变、全突变),快速筛查脆性X综合征可疑患儿。用甲基化特异性PCR方法,检测FMR1基因启动子区CpG岛的异常甲基化情况,进一步诊断脆性X综合征患者,并用Southern印迹技术进行验证。结果1248例先天性智力低下患儿中,筛查出149名不明原因的智低儿童进行了FMR1基因分析,检出脆性X综合征携带者(FMR1基因前突变者)32例(10男22女),脆性X综合征患者(FMR1基因全突变者)12例(9男3女),脆性X综合征检出率为8.05%。结论复式PCR法灵敏、快速、简便,适应于临床和基层开展脆性X综合征筛查。脆性X综合征在先天性智力低下儿童中的发病率高,应对先天性智力低下儿童进行脆性X综合征FMR1基因的分析。     

应用PCR对脆性X综合征进行产前筛查与诊断

目的对脆性X综合征进行产前基因筛查与诊断。方法采用聚合酶链式反应（polymerase chain reaction,PCR）和聚丙烯酰胺凝胶电泳技术,对46例孕妇及其胎儿的脆性X基因（CGG）n重复序列进行检测,同时采用PCR扩增牙幼基因对胎儿性别进行鉴定。结果在46例孕妇及其胎儿中,检出2例前突变携带者孕妇,2例男性患者胎儿。结论采用PCR扩增脆性X基因（CGG）n重复序列,结合扩增牙幼基因进行性别鉴定,可对脆性X综合征进行产前筛查与诊断。     

脆性X综合征FMR1基因CGG重复序列与甲基化的检测

目的建立一种快速、可靠的脆性X综合征的群体筛查方法。方法应用热启动PCR和甲基化特异性PCR（MS-PCR）方法对62例智力低下儿童、12例父母外周血液以及5例高危胎儿的脐带血中FMR1基因CGG重复序列与甲基化状态进行检测。结果采用热启动PCR方法检测79例标本,77例标本的CGG重复数在21～40之间,与正常对照组无明显差异;2例标本未扩增出明显条带。采用MS-PCR方法检测出2例FMR1基因甲基化但CGG重复数在正常范围的患者。结论应用热启动PCR结合MS-PCR方法检测FMR1基因CGG重复数和甲基化,能提高诊断效率,可作为筛查脆性X综合征的首选方法。     

用聚合酶链反应技术对脆性X综合征进行筛查与诊断

目的 建立脆性X综合征大面积快速筛查与诊断的方法。方法 用7-deza-dGTP的PCR法扩增脆性位点智力低下1基因（fragile X mental retardation gene 1,FMR1)的（CGG）的重复区，检测CGG重复数的大小，对脆性X综合征进行诊断。结果 在一家系14个成员中，我们筛查出2例脆性X综合征携带者，5例患者；并用甲基化特异性X综合征男性携带者及患者进行快速鉴定；用甲基化特异性PCR法可以对脆性X综合征患者进行快速诊断。两种方法也适用于脆性X综合征的产前筛查与诊断。     

脆性X综合征的筛查及基因诊断

目的：建立一种简便快速初步筛查脆性X综合征智力缺陷基因FMR－1突变的方法。方法：采用套式PCR技术对新生儿及婴幼儿的足跟血X染色体上基因FMR－1CGG重复序列进行扩增,通过以其拷贝数的鉴定筛查其突变型。结果：共筛查5200全新生儿和婴幼儿,查出1例男婴患者,其母亲是携带者。结论：套式PCR能简便快速地初筛出人群中携带者和可疑患者,对脆性X综合征的早期诊断和产前诊断有应用价值。     

Slowdown PCR法产前快速筛查脆性X综合征

目的研究产前快速筛查脆性X综合征的基因检测方法。方法收集临床疑似脆性X综合征的男性智力低下患儿病例,采集相应患儿外周血,同时收集需要进行胎儿脆性X综合征产前筛查和诊断的孕妇病例,在孕20w收集孕妇的羊水。通过slowdownPCR方法检测FMR1基因(CGG)n三核苷酸重复顺序基因组,并采用测序方法进行验证。结果共检测疑似病例30例,通过slowdown PCR方法简化了检测步骤,缩短了检测时间,整个检测过程缩短至2h,检测PCR产物片段与测序结果完全吻合。结论采用Slowdown PCR方法替代传统普通的PCR,提高了基因扩增效率,解决了由于基因CG含量过高导致PCR扩增困难和稳定性差的技术难题。     

不同民族人群FMR1基因CGG重复序列检测与分析

目的 检测和分析脆性X综合征致病基因FMR1 CGG重复序列在汉族和壮族人群中的多态性分布。方法 采用PCR扩增技术和聚丙烯酰胺凝胶电泳技术对1060例汉族人（男280人，女780人）和283例壮族人（男85人，女198人）FMR1基因CGG重复序列进行分析，并用Southern blot技术对结果进行了验证。结果 汉族人群中共检测到33种等位基因，其中CGG重复序列范围为6～43，壮族人群共检测到27种等位基因，CGG重复序列范围为6～57，两类人群中最大频率等位基因分别为28和29。结论 应用PCR扩增技术进行了脆性X综合征大面积筛查，中国汉族和壮族人群中FMR1基因CGG重复序列变异分布略有差异。     

脆性X综合征的分子生物学研究进展

脆性X综合征是常见的遗传性智力低下性疾病，它是正常FMR1基因5′端非翻译区（CGG）n大量扩增的结果。脆性X综合征的患（CGG）n三核苷酸串联重复序列扩增和异常甲基化，引起FMR1基因失语，导致FMR1蛋白（FMRP）的缺失引起智力低下。FMRP是一种联系核和细胞质之间的RNA结合蛋白。这种蛋白与蛋白质转运，及多聚核糖体和内质网的功能有关。本综述了（CGG）n扩增的分子机制研究和FMRP生物学功能研究的进展。这些研究不仅对搜索人类疾病中三核苷酸重复扩增的分子基础有帮助，并且对认识人类认知和智力方面也能提供依据。     

1035名孕前育龄妇女FMR1基因(CGG)n重复序列多态性分析

目的了解深圳地区孕前育龄妇女脆性X智力低下1(Fragile X Mental Retardation,FMR1)基因(CGG)n重复序列多态性分布特征,为本区脆性X综合征(Fragile X Syndrome,FXS)的预警和孕前筛查提供参考依据。方法收集2017年4月～2018年1月来深圳市龙华区人民医院进行孕前检查的育龄妇女1035名,采用Amp1ideX~(TM) FMR1PCR及毛细管电泳技术对全血标本中FMR1基因(CGG)n重复序列及重复数进行检测,并对检测结果进行统计分析。结果 1035名孕前育龄妇女2070条X染色体中共检出23种不同等位基因,CGG重复数目的变异范围为n=17～63,FMRI基因中最常见的CGG重复数为n=28,占49.32%(1021/2070),其次为n=30和n=29,分别占29.56%(612/2070)和11.16%(231/2070),CGG重复数目n=28的检出频率明显高于n=30和n=29,差异有统计学意义(χ~2=2.6145～4.0352,P0.05)。检出FMR1基因突变5例,突变率为0.24%(5/2070),其中前突变2例(n=63的1例,n=58的1例),占0.10%(2/2070);中间型3例(n=47的2例,n=51的1例),占0.14%(3/2070)。结论深圳地区孕前育龄妇女有一定的FMRI基因突变携带率,加强孕前育龄妇女FMR1筛查,对预防或降低遗传性智力低下并伴有自闭症患儿出生率具有重要意义。     

Molecular screening for fragile X syndrome in mentally handicapped children in Korea.

Fragile X syndrome is one of the most common forms of inherited mental retardation and is caused by the expansion of the CGG trinucleotide repeats in the FMR-1 gene. This study was aimed to facilitate the molecular screening of fragile X syndrome in Korean children with mental retardation of unknown etiology. The subjects were tested by Expand Long Template PCR system in the presence of 7-deaza-dGTP, and then by Southern blot analysis. The PCR method provided rapid and reliable results for the identification of fragile X negative and positive patients. One hundred one mentally retarded children (78 males and 23 females) were screened by PCR amplification, which detected only one abnormal sample. The PCR-positive case was confirmed by the CGG repeat expansion on Southern blot analysis with a positive cytogenetic result. In conclusion, Expand Long Template PCR may be used as the first screening test for detecting the fragile X syndrome.     

FMRP检测在儿童脆性X综合征中诊断价值的实验评价

目的对脆性X智力低下蛋白（fragile X mental retardation protein,FMRP）免疫细胞化学诊断方法并进行临床流行病学评价;利用ROC曲线确定适合本地筛查脆性X综合征的外周血淋巴细胞FMRP免疫组化法的诊断临界点。方法对临床拟诊为不明原因智力低下的的41例不明原因的智力低下患儿,同时进行免疫细胞化学方法进行外周血淋巴细胞FMRP表达检测和7-deza—dGTP PCR法两种方法检查,以目前较为公认的7-deza—dGTP PCR法为诊断金标准,对外周血淋巴细胞FMRP细胞免疫组化法（SP法）进行实验评价,计算其灵敏度、特异度、阳性似然比、阴性似然比等统计学指标。采用ROC曲线确定适合本地筛查脆性X综合征的外周血淋巴细胞FMRP表达率的诊断临界点。结果41例不明原因智力低下患儿中染色体核型分析均正常,其中染色体脆性位点检查异常的1例,约为2．4％。7-deza—dGTP PCR法诊断FXS患者11例,约占26．2％,其中男9例,女2例;ROC计算得出最佳的外周血淋巴细胞FMRP表达率的诊断临界点为46％,灵敏度为90．9％,特异度为93．5％。结论外周血淋巴细胞FMRP免疫细胞化学检测是一种可靠的FXS诊断和筛查方法,具有快速、简便、廉价、相对无创伤性等优点,可进行大样本筛查及标本邮寄快递检测,适宜在我国基层开展早期FXS患者诊断和筛查。     

甲基化特异性三重PCR检测FMR1基因突变的研究

目的探讨甲基化特异性三重PCR检测FMR1基因不同突变类型的价值。方法用甲基化特异性三重PCR方法检测了99例病人的FMR1基因,并用半巢式PCR和Southern印迹杂交方法进行比较。结果用甲基化特异性三重PCR检测出70例男性正常基因型、27例女性正常基因型,1例男性全突变基因型,1例女性前突变基因型,与半巢式PCR和Southern印迹杂交方法的检测结果相符。结论甲基化特异性三重PCR能准确检测FMR1突变的不同类型,适用于对脆性X综合征的临床筛查和诊断。     

脆性X综合征分子诊断研究进展

脆性X智力低下1基因(fragile X mental retardation l gene,FMRI)是脆性X综合征的致病基因,其产物脆性X智力低下蛋白(fragile X mental retardation protein,FMRP)与大脑神经元的发育密切相关.自FMR1基因被鉴定以来,以PCR和Southern印迹杂交为主的分子诊断方法已成为脆性X综合征实验室诊断的主流技术.本文就脆性X综合征分子诊断方法的最新研究进展作一综述.     

Fragile X syndrome is less common than previously estimated.

In 1986, a population study of school children in the city of Coventry gave an overall prevalence in males and females for fragile X syndrome of 1/952. The 29 children diagnosed as having fragile X syndrome in this study have been re-evaluated with molecular diagnostic techniques. Eighteen of the original 29 children have been found not to have the expansion of the FMR1 gene associated with fragile X syndrome. Revised prevalence figures have been calculated giving rise to an overall prevalence figure of 1/2720 (range 1/2198-1/3089). If the four children lost to follow up are also assumed not to have the fragile X syndrome, the revised prevalence figure was 1/5714 (range 1/4762-1/6349). Clinical review of boys with severe mental retardation from this and a subsidiary study show that the clinical features of head circumference greater than the 50th centile, testicular volume greater than the 50th centile, and IQ between 35 and 70 remain helpful in distinguishing boys with fragile X syndrome from those who have non-specific mental retardation.     

Fragile X syndrome

Fragile X syndrome, the most common genetic disorder associated with mental retardation is caused by an expansion of the unstable CGG repeat within the FMR1 gene. Although overgrowth is not the main hallmark of this condition, the fragile X syndrome is usually included in the differential diagnosis of children with mental retardation and excess growth. This review highlights the most recent advances in the field of fragile X research.     

Rapid preparation of diagnostic probes for the fragile X syndrome by direct PCR amplification of human chromosomal DNA

Summary The fragile X syndrome is a common familial form of mental retardation and is associated with a rare fragile site at Xq27.3 (FRAXA). This disorder has recently been reported to correlate with length variations of restriction genomic DNA fragments which may due to the amplification of (CCG)_n trinucleotide repeats located at the FRAXA locus. We described here a rapid preparation method of diagnostic DNA probes for the fragile X syndrome by direct enzymatic amplification of human chromosomal DNA. ThePstI-assay, which is Southern blot analysis of DNA samples probed by PCR products, was shown to be sensitive method for diagnostic purposes to detect the size variations specific in the fragile X syndrome.     

Direct diagnosis by DNA analysis of the fragile X syndrome of mental retardation

BACKGROUND. The fragile X syndrome, the most common form of inherited mental retardation, is caused by mutations that increase the size of a specific DNA fragment of the X chromosome (in Xq27.3). Affected persons have both a full mutation and abnormal DNA methylation. Persons with a smaller increase in the size of this DNA fragment (a premutation) have little or no risk of retardation but are at high risk of having affected children or grandchildren. The passage from premutation to full-mutation status occurs only with transmission from the mother. We have devised a method of identifying carriers of these mutations by direct DNA analysis. METHOD. We studied 511 persons from 63 families with the fragile X syndrome. Mutations and abnormal methylation were detected by Southern blotting with a probe adjacent to the mutation target. Analysis of EcoRI and EagI digests of DNA distinguished clearly in a single test between the normal genotype, the premutation, and the full mutation. RESULTS. DNA analysis unambiguously established the genetic status at the fragile X locus for all samples tested. This method was much more powerful and reliable than cytogenetic testing or segregation studies with closely linked polymorphic markers. The frequency of mental retardation in persons with premutations was similar to that in the general population, whereas all 103 males and 31 of 59 females with full mutations had mental retardation. About 15 percent of those with full mutations had some cells carrying only the premutation. All the mothers of affected children were carriers of either a premutation or a full mutation. CONCLUSIONS. Direct diagnosis by DNA analysis is now an efficient and reliable primary test for the diagnosis of the fragile X syndrome after birth, as well as for prenatal diagnosis and genetic counseling.