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.     

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。     

RETT综合征患儿一例MECP2基因突变分析

目的通过对甲基化CpG结合蛋白2(mehty1-Cp G binding protein 2,MECP2)基因的突变分析,对1例典型的Rett综合征患儿进行基因诊断,并为该家庭提供遗传咨询。方法采用聚合酶链反应和DNA直接测序对先证者及其父母MECP2基因的4个外显子进行序列分析,同时对患儿进行染色体核型分析以排除染色体异常。结果患儿核型正常。针对MECP2基因进行突变分析发现患者存在c.473CT(T158M)杂合突变,其父母未检测到该突变。结论错义突变T158M是导致该RETT家系患者临床表型的主要原因,通过对RETT家系个体Mecp2基因分析可对REET家系进行有效的遗传咨询。     

中国X连锁无丙种球蛋白血症40例基因型表型相关性分析

目的通过中国X连锁无丙种球蛋白血症（XLA）患儿临床表现、免疫功能评价、Bruton＇s酪氨酸激酶（BTK）的表达及BTK基因突变分析,分析基因型和表型间可能存在的关系。方法选取拟诊为XLA患儿,使用抗BTK单克隆抗体通过流式细胞技术分析单核细胞BTK蛋白表达。采用RT-PCR获得患儿cDNA,使用8对不同引物分2步扩增BTKcDNA,PCR产物测序。突变结果通过对DNA外显子相应部位扩增、测序证实。并对确诊XLA患儿的母亲及家族中部分亲属进行BTK蛋白表达和BTK基因分析。结果①40/50例原发性低丙种球蛋白血症患儿经BTK基因突变分析确诊为XLA,以错义突变（16例,40.0%）和无义突变（13例,32.5%）为主。②突变类型为错义突变的患儿平均起病年龄为（1.4±1.1）岁,其他突变类型患儿为（1.4±0.7）岁,差异无统计学意义（P=0.45）。错义突变的发生率随年龄的增长呈上升趋势,无义突变的发生率呈下降趋势。③34/40例（85.0%）B细胞〈0.1%;4例（10.0%）B细胞在1%～2%,其中错义突变2例,无义突变1例,剪接突变1例;2例（5.0%）B细胞为2%,均为错义突变。④血清IgG〈3g·L-1患儿BTK基因突变类型以错义突变和无义突变为主。⑤错义突变患儿BTK蛋白表达水平与其他突变类型无显著差异。⑥6/21例（28.6%）2031C/T多态性患儿伴有严重的关节炎,3/19例（15.8%）无多态性患儿有关节炎表现。⑦28/32例（87.5%）XLA患儿母亲为BTK基因杂合型。结论错义突变可能与确诊年龄较大有关,且某些位点的错义突变可能与较高的外周血B细胞数量和血清IgG水平及正常的BTK蛋白表达水平有关。BTK基因多态性（2031C/T）可能增加关节炎的风险。     

100例视网膜色素变性患者中视紫红质基因突变的筛选与检测

目的 研究视紫红质（rhodopsin,RHO）基因在中国人视网膜色素变性（retinitis pigmentosa,RP）患者中的突变频率，特征及其在RP发病机理中的作用。方法 运用构象敏感凝胶电泳和DNA直接测序方法对100例香港地区中国RP中层得RHO基因全编码区进行突变的筛选与检测。结果 共发现种碱基变异，其中3种为沉默型突变，两种为错义突变，1种为缺失突变。P347L在1例55岁女性患者及其同样患RP的3名子女 中检出。327（1－bp del）首次在1例53岁的晚发型RP患者中发现。其26岁的女儿同样携带该突变，但目前除眼底色素上皮出现斑点外，还没有RP的任何症状。上述两种突变均未在对照组中发现。结论 100例RP患者中检出两例携带RHO基因突变，由此可预测香港地区约为2．0％（95％的可信区间为0．2％－7．0％）的RP是由RHO基因突变所致。P347L突变改变了RHO基因C末端一段高度保守的氨基酸序列，致使视紫红质蛋白在细胞P内的运输发生障碍。P327（1 bp del）使突变蛋白的羧基末端失去了原有的磷酸化位点及一段高度保守的功能区，其可能的致病机理有待在今后的研究中通过建立相应的转基因模型或细胞培养系统来阐明。     

粘多糖贮积症Ⅱ型患者艾杜糖-2-硫酸酯酶基因常见突变的检测

目的 探讨并建立粘多糖贮积症Ⅱ型（mucopolysaccharidosis Ⅱ,MPSⅡ)患者艾杜糖－2－硫酸酯酶（iduronate-2-sulphatase,IDS)基因常见突变的检测方法。方法 应用聚合酶链反应－单链构象多态性（polymerase chain reaction-single strand conformation polymorphism,PCR-SSCP）对IDS基因突变热点外显子3、8和9进行点突变检测；应用DNA测序对PCR－SSCP检出的突变进行序列分析；应用聚合酶链反应－限制性片段长度多态性（polymerase chain reaction-restriction fragment length polymorphism,PCR-RFLP)对DNA测序的结果进行检测。结果 以PCR－SSCP发现该患者的IDS基因外显子9有明显异常泳动的条带；DNA测序发现患儿的外显子9发生点突变（C1672T），从而导致患者艾杜糖－2－硫酸酯酶蛋白发生氨基酸替换（R468W）；PCR－RFLP电泳检测结果显示粘多糖贮积症Ⅱ型患者仅出现554bp 1条带，而患儿父母出现257bp和297bp 2条带，进一步验证了序列分析的结果。结论 PCR－SSCP分析、DNA序列分析和PCR－RFLP分析是诊断MPSⅡ的有效方法，三者联合使用可以相互验证、互为补充，提高基因诊断的准确率和成功率。     

三例Rett综合征患者的 MECP2基因变异分析

目的对3例Rett综合征患者进行MECP2基因变异分析, 明确其致病原因。方法采集3例患者及其父母外周血提取DNA, 设计特异性引物覆盖基因全外显子及其侧翼序列, 通过PCR及Sanger测序法和多重连接探针扩增技术(multiplex ligation-dependent probe amplification, MLPA)检出患者MECP2基因的变异。结果 3个家系的先证者MECP2基因的Sanger测序及MLPA结果分别为, 家系1发生c.965C>G杂合变异, 家系2发生c.1157₁197del41杂合缺失变异;家系3发生第4外显子部分缺失杂合变异。3个家系先证者的父母均未携带相应的变异, 均为新发变异。其中MECP2基因c.965C>G和c.1157₁197del41变异为未报道的新变异。结论根据美国医学遗传学与基因组学学会指南并结合临床表现对上述变异进行分析后推测3个变异均为可能致病性变异, 是这3个Rett综合征家系的致病原因。本研究结果丰富了MECP2基因的变异谱, 为家系遗传咨询和产前诊断提供了依据。     

以T613M为突变位点合并有癫痫发作家族史的长QT综合征1例

KCNH2基因突变可导致长QT综合征2型(LQTS2),近年来各类型位点的基因突变被不断报道。文中报道了1例因T613M位点变异所致的KCNH2基因突变的患儿,且患儿其父有同样位点的变异。患儿女性,12岁,临床表现为间断胸闷、心悸及晕厥,其父有癫痫样发作史,基因检测发现该患儿及其父亲携带KCNH2基因c.1838C>T(p.T613M)错义突变,结合患儿临床表现、基因检测结果,患儿诊断为LQTS2。检索相关文献资料,T613M位点突变不仅与长QT综合征(LQTS)有关,也可能引起神经异常改变,进一步提示我们基因检测明确基因突变类型,有助于对遗传性疾病更加精准化治疗。     

中国福建遗传性乳腺癌BRCA1基因突变分析

目的研究福建遗传性乳腺癌患者BRCA1基因突变位点及携带情况。方法对20例遗传性乳腺癌患者血液标本进行检测,对其BRCA1基因第11号外显子全序列进行DNA测序。结果20例标本中检出5患者存在共计9种BRCA1基因突变,其中3个为新发现位点（错义突变1159T〉C,4071A〉C;同义突变4122C〉T）;其它6个已报道位点中2个（2201C〉T,2430T〉C）为同义突变,其余4个（2685T〉C,2731C〉T,3232A〉G,3667A〉G）属错义突变,本研究中BRCA1突变率为25%。结论福建遗传性乳腺癌患者BRCA1基因突变具有地域性特征,开展BRCA1基因突变检测有助于本地区女性患癌风险评估和早期诊断。     

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。     

MECP2 gene mutation analysis in Chinese patients with Rett syndrome

Rett syndrome (RTT) is a progressive neurodevelopmental disorder that affects almost exclusively girls. Mutations in the X-linked methyl-CpG-binding protein 2 gene (MECP2) have been found to be a cause. In order to study the spectrum of MECP2 mutations in Chinese patients, we employed PCR and sequencing of the coding region of MECP2 gene in 31 Chinese cases of classical sporadic RTT. Mutations in MECP2 were found in about 55%. Twelve different mutations in exon 3 were identified in 17 of these 31 patients; two of these are novel. A novel missense variant was detected in the C-terminal region in a patient and her father who was normal. In addition, there was a single nucleotide variant in the 3'UTR.     

<Emphasis Type="Italic">MECP2 </Emphasis>and <Emphasis Type="Italic">CDKL5</Emphasis> gene mutation analysis in Chinese patients with Rett syndrome

Rett syndrome (RTT) is a progressive neurodevelopmental disorder that is caused by mutations in the X-linked methyl-CpG-binding protein2 (MECP2) gene. In this study, the MECP2 sequences in 121 unrelated Chinese patients with classical or atypical RTT were screened for deletions and mutations. In all, we identified 45 different MECP2 mutations in 102 of these RTT patients. The p. T158M mutation (15.7%) was the most common, followed in order of frequency by p. R168X (11.8%), p. R133C (6.9%), p. R270X (6.9%), p. G269fs (6.9%), p. R255X (4.9%), and p. R306C (3.9%). In addition, we identified five novel MECP2 mutations: three missense (p. K305E, p. V122M, p. A358T), one insertion (c.45-46insGGAGGA), and one 22 bp deletion (c.881-902del22). Large deletions represented 10.5% of all identified MECP2 mutations. Conversely, mutations in exon 1 appeared to be rare (0.9%). The remaining cases without MECP2 mutations were screened for the cyclin-dependent kinase-like 5 (CDKL5) gene using denaturing high-performance liquid chromatography (DHPLC). One synonymous mutation (p. I72I) was found in exon 5, suggesting that CDKL5 is a rare cause of RTT. The overall MECP2 mutation detection rate for this patient series was 84.3:87.9% in 107 classical RTT cases and 57.1% in 14 atypical RTT cases. Moreover, there were two patients with homozygous mutations and normal female karyotypes. However, we did not pinpoint a significant relationship between genotype and phenotype in these cases.     

Mutation screening in Rett syndrome patients

Rett syndrome (RTT) was first described in 1966. Its biological and genetic foundations were not clear until recently when Amir et al reported that mutations in the MECP2 gene were detected in around 50% of RTT patients. In this study, we have screened the MECP2 gene for mutations in our RTT material, including nine familial cases (19 Rett girls) and 59 sporadic cases. A total of 27 sporadic RTT patients were found to have mutations in the MECP2 gene, but no mutations were identified in our RTT families. In order to address the possibility of further X chromosomal or autosomal genetic factors in RTT, we evaluated six candidate genes for RTT selected on clinical, pathological, and genetic grounds: UBE1 (human ubiquitin activating enzyme E1, located in chromosome Xp11.23), UBE2I (ubiquitin conjugating enzyme E2I, homologous to yeast UBC9, chromosome 16p13.3), GdX (ubiquitin-like protein, chromosome Xq28), SOX3 (SRY related HMG box gene 3, chromosome Xq26-q27), GABRA3 (gamma-aminobutyric acid type A receptor alpha3 subunit, chromosome Xq28), and CDR2 (cerebellar degeneration related autoantigen 2, chromosome 16p12-p13.1). No mutations were detected in the coding regions of these six genes in 10 affected subjects and, therefore, alterations in the amino acid sequences of the encoded proteins can be excluded as having a causative role in RTT. Furthermore, gene expression of MECP2, GdX, GABRA3, and L1CAM (L1 cell adhesion molecule) was also investigated by in situ hybridisation. No gross differences were observed in neurones of several brain regions between normal controls and Rett patients.     

Molecular analysis of Japanese patients with Rett syndrome: Identification of five novel mutations and genotype-phenotype correlation

Rett syndrome is an X-linked dominant neurodevelopmental disorder that affects females almost exclusively. The recent identification of mutations of the methyl-CpG-binding protein 2 gene (MECP2) in patients with RTT, encouraged us to analyze the gene in 37 Japanese patients divided into classical RTT (14 cases), variant RTT (13 cases), and mentally retarded patients with Rett-like features (10 cases). Mutations in MECP2 were identified from most of the patients with classical and variant RTT (25 of 27 cases). Six reported common mutations were detected in 17 cases, and rare single nucleotide substitutions were found in 3 patients. In addition, one insertion mutation (1189insA) and four deletion mutations including one double deletion mutant (451delG, 100del4, 1124del53 and 881del289 plus 1187del8) were newly identified. In the 10 mentally retarded patients with Rett-like features, however, no mutation was detected in the coding region of MECP2. The finding of MECP2 mutations in 92.5% of patients with RTT indicates that RTT fulfilling the diagnostic criteria are due to genetic alteration.     

Analysis of Hungarian patients with Rett syndrome phenotype for MECP2, CDKL5 and FOXG1 gene mutations

Rett syndrome (RTT) is characterized by a relatively specific clinical phenotype. We screened 152 individuals with RTT phenotype. A total of 22 different known MECP2 mutations were identified in 42 subjects (27.6%). Of the 22 mutations, we identified 7 (31.8%) frameshift-causing deletions, 4 (18.2%) nonsense, 10 (45.5%) missense mutations and one insertion (4.5%). The most frequent pathologic changes were: p.Thr158Met (14.2%) and p.Arg133Cys (11.9%) missense, and p.Arg255Stop (9.5%) and p.Arg294Stop (9.5%) nonsense mutations. We also detected the c.925C >T (p.Arg309Trp) mutation in an affected patient, whose role in RTT pathogenesis is still unknown. Patients without detectable MECP2 defects were screened for mutations of cyclin-dependent kinase-like 5 (CDKL5) gene, responsible for the early-onset variant of RTT. We discovered two novel mutations: c.607G >T resulting in a termination codon at aa203, disrupting the catalytic domain, and c.1708G >T leading to a stop at aa570 of the C terminus. Both patients with CDKL5 mutation presented therapy-resistant epilepsy and a phenotype fitting with the diagnosis of early-onset variant of RTT. No FOXG1 mutation was detected in any of the remaining patients. A total of 110 (72.5%) patients remained without molecular genetic diagnosis that necessitates further search for novel gene mutations in this phenotype. Our results also suggest the need of screening for CDKL5 mutations in patients with Rett phenotype tested negative for MECP2 mutations.     

MECP2 structural and 3'-UTR variants in schizophrenia, autism and other psychiatric diseases: a possible association with autism.

Mutations in the gene coding for methyl-CpG-binding protein 2 (MECP2) cause Rett syndrome (RTT) and have also been reported in a number of X-linked mental retardation syndromes. Furthermore, putative mutations recently have been described in a few autistic patients and a boy with language disorder and schizophrenia. In this study, DNA samples from individuals with schizophrenia and other psychiatric diseases were scanned in order to explore whether the phenotypic spectrum of mutations in the MECP2 gene can extend beyond the traditional diagnoses of RTT in females and severe neonatal encephalopathy in males. The coding regions, adjacent splicing junctions, and highly conserved segments of the 3'-untranslated region (3'-UTR) were examined in 214 patients, including 106 with schizophrenia, 24 with autism, and 84 patients with other psychiatric diseases by detection of virtually all mutations-single strand conformation polymorphism (SSCP) (DOVAM-S). To our knowledge, this is the first analysis of variants in conserved regions of the 3'-UTR of this gene. A total of 5.2 kb per haploid gene was analyzed (1.5 Mb for 214 patients). A higher frequency of missense and 3'-UTR variants was found in autism. One missense and two 3'-UTR variants were found in 24 patients with autism versus one patient with a missense change in 144 ethnically similar individuals without autism (P = 0.009). These mutations suggest that a possible association between MECP2 mutations and autism may warrant further study.     

Rett syndrome: analysis of MECP2 and clinical characterization of 31 patients

Only recently have mutations in MECP2 been found to be a cause of Rett Syndrome (RTT), a neuro-developmental disorder characterized by mental retardation, loss of expressive speech, deceleration of head growth and loss of acquired skills that almost exclusively affects females. We analysed the MECP2 gene in 31 patients diagnosed with RTT. Sequencing of the coding region and the splice sites revealed mutations in 24 females (77.40%). However, no abnormalities were detected in any of the parents that were available for investigation. Eleven mutations have not been described previously. Confirming two earlier studies, we found that most mutations are truncating and only a few of them are missense mutations. Several females carrying the same mutation display different phenotypes indicating that factors other than the type or position of mutations influence the severity of RTT. Four females with RTT variants were included in the study. Three of these presented with preserved speech while the fourth patient with congenital RTT lacked the initial period of normal development. Detection of mutations in these cases reveals that they are indeed variants of RTT. They represent the mild and the severe extremes of RTT. Conclusions: mutations in MECP2 seem to be the main cause for RTT and can be expected to be found in approximately 77% of patients that fulfil the criteria for RTT. Therefore analysis of MECP2 should be performed if RTT is suspected. Three mutation hotspots (T158M, R168X and R255X) were confirmed and a further one (R270X) newly identified. We recommend screening for these mutations before analysing the coding region.     

Isolation of MECP2-null Rett Syndrome patient hiPS cells and isogenic controls through X-chromosome inactivation

Rett syndrome (RTT) is a neurodevelopmental autism spectrum disorder that affects girls due primarily to mutations in the gene encoding methyl-CpG binding protein 2 (MECP2). The majority of RTT patients carry missense and nonsense mutations leading to a hypomorphic MECP2, while null mutations leading to the complete absence of a functional protein are rare. MECP2 is an X-linked gene subject to random X-chromosome inactivation resulting in mosaic expression of mutant MECP2. The lack of human brain tissue motivates the need for alternative human cellular models to study RTT. Here we report the characterization of a MECP2 mutation in a classic female RTT patient involving rearrangements that remove exons 3 and 4 creating a functionally null mutation. To generate human neuron models of RTT, we isolated human induced pluripotent stem (hiPS) cells from RTT patient fibroblasts. RTT-hiPS cells retained the MECP2 mutation, are pluripotent and fully reprogrammed, and retained an inactive X-chromosome in a nonrandom pattern. Taking advantage of the latter characteristic, we obtained a pair of isogenic wild-type and mutant MECP2 expressing RTT-hiPS cell lines that retained this MECP2 expression pattern upon differentiation into neurons. Phenotypic analysis of mutant RTT-hiPS cell-derived neurons demonstrated a reduction in soma size compared with the isogenic control RTT-hiPS cell-derived neurons from the same RTT patient. Analysis of isogenic control and mutant hiPS cell-derived neurons represents a promising source for understanding the pathogenesis of RTT and the role of MECP2 in human neurons.