中国Rett综合征患儿突变基因的亲源分析

目的 明确中国Rett综合征(Rett syndrome,RTT)患儿致病基因甲基化CpG结合蛋白2(methyl-CpG-binding protein 2,MECP2)的突变亲源.方法 对115例经基因突变分析证实存在MECP2突变的患儿进行第3内含子测序分析,寻找单核苷酸多态性(single nucleotide polymorphism,SNP)位点.对发现SNP患儿行等位基因特异性PCR扩增,通过比较患儿及其父亲SNP碱基序列,判定患儿突变基因所在染色体亲源.结果 115例患儿中76例存在至少一种SNP.在中国RTT患儿中发现3个热点SNP.76例患儿中73例突变位于父源X染色体,3例突变位于母源X染色体.结论 我国RTT患儿MECP2突变以父源突变为主.     

中国Rett综合征患儿突变基因的亲源分析

Objective To identify the parental origin of methyl-CpG-binding protein 2 (MECP2)gene mutations in Chinese patients with Rett syndrome. Methods Single nucleotide polymorphisms (SNPs) in intron 3 of the MECP2 gene were analyzed by PCR and sequencing in 115 patients with Rett syndrome.Then sequencing of the SNP region was performed for the fathers of the patients who had at least one SNP,to determine which allele was from the father. Then allele-specific PCR was performed and the products were sequenced to see whether the allele from father or mother harbored the mutation. Results Seventy-six of the 115 patients had at least one SNP. Three hot SNPs were found in these patients. They were: IVS3+22C＞G, IVS3+266C＞T and IVS3+683C＞T. Among the 76 cases, 73 had a paternal origin of MECP2 mutations, and the other 3 had a maternal origin. There were multiple types of MECP2 mutation of the paternal origin, including 4 frame shift, 2 deletion and 67 point (56 C＞T, 6 C＞G, 2 A＞G, 2 G＞T and 1 A＞T) mutations. The mutation types of the 3 ptients with maternal origin included 2 frame shift and 1 point (C＞T) mutation. Conclusion In Chinese RTT patients, the MECP2 mutations are mostly of paternal origin.     

Rett综合征和DNA甲基化

DNA甲基化是一种在生物界普遍存在的生命现象,在染色体失活和基因印记以及基因沉默方面起着重要的作用。甲基化CpG结合蛋白2(methyl-CpG-binding protein2,MeCP2)作为一种转录抑制因子能够与甲基化的DNA结合,在基因的转录过程中发挥主要作用,其编码基因MECP2是神经发育性遗传病-Rett综合征的主要致病基因,现主要介绍DNA甲基化和Rett综合征之间的关系。     

Rett综合征MECP2基因突变分析

目的 分析我国典型的Rett综合征患儿甲基化CpG结合蛋白－2基因（methyl-CpG-binding protein 2,MECP2）突变。方法 使用PCR扩增、单链构象多态性分析、PCR产物克隆和DNA测序的方法。检测分析了26例Rett综合征患儿、其父母和其中2例患儿的妹妹MECP2基因3个外显子的基因突变。结果 26例Rett综合征患儿中发现14例有9种类型MECP2基因的杂合性突变，突变均位于第3外显子。其中7例有3种错义突变：C473T（T158M)4例,C674G(P225R)1例，C916T（R306C）2例；4例有3种无义突变：C502T（R168X）2例，C763T（R255X）1例，C880T（R294X）1例；2种由于缺失导致的突变：1例为1152del 44bp和1例1158－1167／1171－1186del 26bp；1鲍由于碱基插入导致的移码突变：874insA。1158－1167／1171－1186del 26bp和874insA突变为首次报千，突变均为新生突变。此外，新发现了一种源于你亲的错义变异1141G（P381A）。结论 我国Rett综合征患儿存在MECP2基因突变，典型的Rett综合征MECP2基因突变率大于50％。     

甲基CpG结合蛋白2与Rett综合征

DNA甲基化转录抑制的机制之一是通过在甲基化DNA上结合上特异的转录抑制因子（repressors)发挥作用的,这种转录抑制因子即为甲基CpG结合蛋白（MeCP)。现已发现了多种甲基CpG结合蛋白,如MeCP1和MeCP2等,本主要介绍MeCP2的研究状况及与Rett综合征的关系。     

Rett综合征分子遗传学研究进展

Rett综合征 (RTT)是一种严重影响儿童精神运动发育的神经遗传病。目前提出的遗传方式主要包括 X连锁显性遗传 ,代谢干扰学说及线粒体受累学说。目前进行的 X染色体排除作图 ,基因型分析及多点连锁分析将家族性 RTT基因定位于 Xq2 8。在散发性及家族性 RTT均检查到 X连锁甲基 Cp G结合蛋白 2基因存在突变。动物模型的建立将会加深对其病理生理机制的认识     

甲基CpG结合蛋白2与 Rett综合征

DNA甲基化转录抑制的机制之一是通过在甲基化DNA上结合上特异的转录抑制因子(repressors)发挥作用的,这种转录抑制因子即为甲基CpG结合蛋白(MeCP).现已发现了多种甲基CpG结合蛋白,如MeCP1和MeCP2等,本文主要介绍MeCP2的研究状况及与Rett综合征的关系     

Rett综合征的研究进展

Rett综合征（Rrrr）是一种主要影响女性的神经发育性疾病,MECP2是Rrrr的致病基因,大约80％的患者携带有MECP2基因突变。临床诊断主要依靠国际上通用的诊断标准。MECP2基因型与表型之间有一定的相关性。动物模型的建立将会加深对其病理生理机制的认识。本文对该病的临床特征、诊断、遗传学研究、遗传型／表现型的关系及动物模型等方面的研究加以综述,为进一步研究RTT的致病机制提供相关的资料。     

Rett综合征的基础研究

摘要：Rett综合征(RTT)是一种由MECP2基因的突变引起、X-连锁的神经发育性疾病。临床诊断主要依靠国际上通用的诊断标准。 MECP2基因型与表型之间有一定的相关性。动物模型的建立将会加深对其病理生理机制的认识。本文对该病的基础研究加以综述，为进一步研究其致病机制提供相关的资料。     

5例Rett综合征样表型患儿的基因突变分析

目的 探讨5例Rett综合征（RTT）样表型患儿的临床特征及对遗传学结果进行分析。方法 收集5例RTT样表型患儿的临床资料,应用全外显子组测序技术及拷贝数变异检测对患儿及其父母进行遗传学分析,寻找致病性变异。结果 结合患儿的临床特征及基因突变分析结果,4例患儿诊断为RTT,1例患儿诊断为MECP2重复综合征（MDS）。结论 具有RTT样表型的遗传性疾病中,可能存在多种基因突变形式,应将基因诊断作为重要的辅助诊断标准。     

Gross rearrangements of the MECP2 gene are found in both classical and atypical Rett syndrome patients

MECP2 mutations are identifiable in approximately 80% of classic Rett syndrome (RTT), but less frequently in atypical RTT. We recruited 110 patients who fulfilled the diagnostic criteria for Rett syndrome and were referred to Cardiff for molecular analysis, but in whom an MECP2 mutation was not identifiable. Dosage analysis of MECP2 was carried out using multiplex ligation dependent probe amplification or quantitative fluorescent PCR. Large deletions were identified in 37.8% (14/37) of classic and 7.5% (4/53) of atypical RTT patients. Most large deletions contained a breakpoint in the deletion prone region of exon 4. The clinical phenotype was ascertained in all 18 of the deleted cases and in four further cases with large deletions identified in Goettingen. Five patients with large deletions had additional congenital anomalies, which was significantly more than in RTT patients with other MECP2 mutations (2/193; p<0.0001). Quantitative analysis should be included in molecular diagnostic strategies in both classic and atypical RTT.     

Gross rearrangements in the MECP2 gene in three patients with Rett syndrome: implications for routine diagnosis of Rett syndrome

Since 1999, many laboratories have confirmed that mutations in the MECP2 gene are the primary cause of Rett syndrome (RTT or RS) and identified mutations in 70 to 90% of the sporadically affected girls. Most of the screenings are PCR-based and restricted to the coding part of the gene and therefore prone to miss gross rearrangements. By Southern blot analysis we identified large deletions (>1 kb) in three female patients with classical, severe Rett syndrome. Further characterization by semi-quantitative PCR and amplification of junction fragments confirmed the presence of a 7.6-kb deletion in one patient and an 8.1-kb deletion in the other patient, both including exon 3 and the coding part of exon 4. The exact nature of the rearrangement in the third patient remained elusive. These results underline the importance of screening for major genomic rearrangements in Rett syndrome. Hum Mutat 22:116-120, 2003.     

Large deletions of the MECP2 gene detected by gene dosage analysis in patients with Rett syndrome

MECP2 mutations are responsible for Rett syndrome (RTT). Approximately a quarter of classic RTT cases, however, do not have an identifiable mutation of the MECP2 gene. We hypothesized that larger deletions arising from a deletion prone region (DPR) occur commonly and are not being routinely detected by the current PCR-mediated screening strategies. We developed and applied a quantitative PCR strategy (qPCR) to samples referred for diagnostic assessment from 140 patients among whom RTT was strongly suspected and from a second selected group of 31 girls with classical RTT. Earlier MECP2 mutation screening in both groups of patients had yielded a wild-type result. We identified 10 large deletions (7.1%) within the first group and five deletions in the second group (16.1%). Sequencing of the breakpoints in 11 cases revealed that eight cases had one breakpoint within the DPR. Among seven cases, the breakpoint distant to the DPR involved one of several Alu repeats. Sequence analysis of the junction sequences revealed that eight cases had complex rearrangements. Examination of the MECP2 genomic sequence reveals that it is highly enriched for repeat elements, with the content of Alu repeats rising to 27.8% in intron 2, in which there was an abundance of breakpoints among our patients. Furthermore, a perfect chi sequence, known to be recombinogenic in E. coli, is located in the DPR. We propose that the chi sequence and Alu repeats are potent factors contributing to genomic rearrangement. We suggest that routine mutation screening in MECP2 should include quantitative analysis of the genomic sequences flanking the DPR.     

Parental origin of de novo MECP2 mutations in Rett syndrome

Rett syndrome (RTT) is a neurodevelopmental disorder occurring almost exclusively in females as sporadic cases. Recently, DNA mutations in the MECP2 gene have been detected in approximately 70% of patients with RTT. To explain the sex-limited expression of RTT, it has been suggested that de novo X-linked mutations occur exclusively in male germ cells resulting therefore only in affected daughters. To test this hypothesis, we have analysed 19 families with RTT syndrome due to MECP2 molecular defects. In seven informative families we have found by DHPLC a nucleotide variant which could be used to differentiate between the maternal and the paternal allele. In each subject investigated from these families, we have amplified specifically each allele and sequenced allele-specific PCR products to identify the allele bearing the mutation as well as the parental origin of each X chromosome. This approach allowed us to determine the parental origin of de novo mutations in all informative families. In five cases, the de novo MECP2 mutations have a paternal origin and in the two other cases a maternal origin. In all transitions at CpG, the de novo mutation observed was of paternal origin. The high frequency of male germ-line transmission of the mutation (71% of RTT informative cases) is consistent with a predominant occurrence of the disease in females.     

DHPLC analysis of the MECP2 gene in Italian Rett patients

Rett Syndrome (RTT) is an X‐linked dominant neurodevelopmental disorder, which almost exclusively affects girls, with an estimated prevalence of one in 10,000–15,000 female births. Mutations in the methyl CpG binding protein 2 gene (MECP2) have been identified in roughly 75% of classical Rett girls. The vast majority of Rett cases (99%) are sporadic in origin, and are due to de novo mutations. We collected DNA samples from 50 Italian classical Rett girls, and screened the MECP2 coding region for mutations by denaturing high‐performance liquid chromatography (DHPLC) and subsequent direct sequencing. DHPLC is a recently developed method for mutation screening which identifies heteroduplexes formed in DNA samples containing mismatches between wild type and mutant DNA strands, combining high sensitivity, reduced cost per run, and high throughput. In our series, 19 different de novo MECP2 mutations, eight of which were previously unreported, were found in 35 out of 50 Rett girls (70%). Seven recurrent mutations were characterized in a total of 22 unrelated cases. Initial DHPLC screening allowed the identification of 17 out of 19 different mutations (90%); after optimal conditions were established, this figure increased to 100%, with all recurrent MECP2 mutations generating a characteristic chromatographic profile. Detailed clinical data were available for 27 out of 35 mutation carrying Rett girls. Milder disease was detectable in patients carrying nonsense mutation as compared to patients carrying missense mutations, although this difference was not statistically significant (P = 0.077). Hum Mutat 18:132–140, 2001. © 2001 Wiley‐Liss, Inc.     

Homozygosity for MECP2 gene in a girl with classical Rett syndrome

We report a 21 year-old girl with classical Rett syndrome (RS) based on clinical diagnosis. The molecular testing of MECP2 gene revealed that the patient is homozygous for a de novo 473C > T mutation, causing the T158M amino acid change. Chromosome analysis showed a normal karyotype, and the haplotype analysis ruled out the possibility of parental disomy or microdeletion in MECP2 gene. Cultured fibroblast analysis reveals a mosaic for the mutation. This is a documented case of a homozygous female with RS.