应用高分辨熔解曲线技术检测中国人Wilson病的常见基因突变

目的 应用PCR-高分辨熔解曲线分析技术检测中国人Wilson病(Wilson disease,WD)患者中ATP7B基因内高频突变区第8和13外显子.方法 酚-氯仿法提取外周全血基因组DNA;PCR扩增患者ATP7B基因第8和13外显子及两个外显子中的突变热点区域,PCR产物经HR-1进行高分辨熔解曲线分析;进一步以限制性内切酶或(和)DNA测序法对高分辨熔解曲线检测结果进行验证.结果 在30例WD患者中,检测到R778L纯合子3例,R778L杂合子6例,P992L杂合子6例,P992D/S975Y的复合杂合子1例,R778L/P992L复合杂合子2例和R778L/752.33delG复合杂合子1例.本组样本中,R778L、P992L和S975Y的基因频率分别为25%、15%和1.67%.测序及限制性内切酶分析结果完全与高分辨熔解曲线分析结果一致.结论 高分辨熔解曲线分析检测ATP7B基因突变具有简便、快速、特异和灵敏等优点,可作为Wilson病患者及携带者突变筛查的优选方法.     

High-resolution Melting Facilitates Mutation Screening of PYGM in Patients with McArdle Disease

Mutations in PYGM , encoding the muscle-specific glycogen phosphorylase (myophosphorylase), are responsible for McArdle disease. Among Caucasians, a large proportion of patients are homozygous for the R50X mutation, but other mutations can affect all the 20 exons of PYGM , making mutation detection laborious.
We have developed a high-resolution melting (HRM) assay for mutation detection in PYGM . Twelve McArdle patients were investigated, in whom pre-screening had ruled out homozygosity or compound heterozygosity for the two common G205S and R50X mutations. In total, we identified 16 different variations. Thirteen of these are pathogenic, and three were classified as polymorphisms. Nine variations had not previously been described. One of the novel mutations, c.2430C > T, was initially predicted to result in a silent G810G change, but cDNA analysis demonstrated that the mutation led to abnormal mRNA processing.
The HRM protocol reduced the need for direct sequencing by approximately 85%, and is a good approach to search for new mutations in PYGM .     

A proposed molecular diagnostic flowchart for myophosphorylase deficiency (McArdle disease) in blood samples from Spanish patients

McArdle disease is a metabolic myopathy due to molecular defects in the myophosphorylase gene (PYGM), usually diagnosed in muscle biopsy. The aims of this study were to characterize genetically a large series of patients and to establish a protocol of molecular diagnosis on blood samples. We studied 55 Spanish unrelated patients with McArdle disease. Screening for the three more frequent mutations in the PYGM gene in the Spanish population (c.148C>T, p.R50X; c.613G>A, p.G205S; and c.2392T>C, p.W798R) were performed with polymerase chain-reaction and restriction fragment length polymorphism (PCR-RFLP) methods. To identify other mutant alleles, the coding region of PYGM gene was sequenced. The p.R50X mutation was observed in 38 patients, the p.G205S substitution in eight, and the p.W798R change in nine. Nine novel mutations, five missense (c.247A>T, p.I83F; c.521G>A, p.G174D; c.1094C>T, p.A365V; c.1468C>T, p.R490W; and c.1730A>G, p.Q577R), one nonsense mutation (c.2352C>A, p.C784X), three frameshift (c.402del, p.N134KfsX161; c.212_218dup, p.Q73HfsX7; c.1470dup, p.R491AfsX7), and nine previously reported mutations were found. In addition, we also updated the molecular data of 95 unrelated patients with McArdle disease studied thus far in our center. Of these patients, 56 were either homozygous or compound heterozygous for the p.R50X, p.G205S, or p.W798R mutation. By including in the molecular diagnosis protocol sequencing of the exons 1, 14, 17 and 18 of the PYGM gene, 16 further patients were characterized, and therefore we were able to detect the molecular defect in 72 out of 95 patients. A proposed molecular diagnosis protocol of the disease based on blood DNA would avoid muscle biopsy in 75.8% [95% confidence interval (95% CI): 62.1%-78.6%] of patients with McArdle disease.     

Biochemical and mutational analyses of the cathepsin c gene (CTSC) in three North American families with Papillon Lefèvre syndrome

Papillon Lefèvre syndrome (PLS) is an autosomal recessive disorder characterized by palmoplantar hyperkeratosis and severe periodontitis. The disease is caused by mutations in the cathepsin C gene (CTSC) that maps to chromosome 11q14. CTSC gene mutations associated with PLS have been correlated with significantly decreased enzyme activity. Mutational analysis of the CTSC gene in three North American families segregating PLS identified four mutations, including a novel mutation p.G139R. All mutations were associated with dramatically reduced CTSC protease enzyme activity. A homozygous c.96T>G transversion resulting in a p.Y32X change was present in a Mexican PLS proband, while one Caucasian PLS proband was a compound heterozygote for the p.Y32X and p.R272P (c.815G>C) mutations. The other Caucasian PLS proband was a compound heterozygote for c.415G>A transition and c.1141delC mutations that resulted in a p.G139R and a frameshift and premature termination (p.L381fsX393), respectively. The c.415G>A was not present in more than 300 controls, suggesting it is not a CTSC polymorphism. Biochemical analysis demonstrated almost no detectable CTSC activity in leukocytes of all three probands. These mutations altered restriction enzyme sites in the highly conserved CTSC gene. Sequence analysis of CTSC exon 3 confirmed the previously reported p.T153I polymorphism in 4 of the 5 ethnically diverse populations studied.     

NF1 gene analysis focused on CpG-rich exons in a cohort of 93 patients with neurofibromatosis type 1

We studied the NF1 gene in 93 unrelated patients with neurofibromatosis type1, focusing the analysis on four exons that contain the highest number of possible mutations occurring at CpG sites. We used denaturing gradient gel electrophoresis to analyse exons 16, 28, 29 and 49, which contain 45 (25%) of the 183 possible mutations that could occur at the 120 CpG dinucleotides of the coding sequence. Six different mutations were identified, five of which are novel: two truncating mutations, W1810X and 5448insG, located in exon29; two splice defects leading to exon29 skipping, 5206-2A>G and 5546G>A; and one missense mutation, L844F, located in exon16. The already described R1748X mutation located in exon29 was found in two unrelated patients. The 5546G>A and R1748X mutations are located at CpG sites, whereas the W1810X involves a CpNpG site. Four novel polymorphisms, which may be helpful for family studies, were also identified. Overall, all but one mutations were found in exon29, a result which suggests that all the CpG sites of the NF1 coding sequence do not have the same mutability, and that exon29, the most CpG-rich exon, contains mutational hotspots associated with NF1.     

Expression of lysosomal acid lipase mutants detected in three patients with cholesteryl ester storage disease

Lysosomal acid lipase (LAL) gene mutations were identified in three patients with cholesteryl ester storage disease (CESD). Direct sequencing of genomic DNA revealed that: patient 1 was a compound heterozygote for a P181L mutation and an A to G3' splice site substitution that causes skipping of exon 7, with a loss of 49 amino acids from LAL (delta 205-253); patient 2 was a compound heterozygote for a G66V mutation and a 5' splice site mutation (G to A) that leads to skipping of exon 8 (delta 254-277); and patient 3 was a compound heterozygote for a L273S mutation and an unidentified null allele. Furthermore, patients 2 and 3 showed a novel G-2A polymorphism that could be detected by an Xbal restriction fragment length polymorphism. All these mutants and a previously reported H274Y allele were expressed in vitro in HeLa cells using the vaccinia T7 expression system. The resulting recombinant proteins were inactive towards cholesteryl oleate and trioleylglycerol, demonstrating the direct involvement of these mutations in the pathogenesis of CESD. Immunoblotting of normal LAL expressed in HeLa cells revealed four major molecular forms, at least two of high molecular mass (54 and 50-51 kDa) and two of low molecular mass (42 and 43 kDa). L273S and P181L substitutions and delta 254-277 were shown to result in altered LAL molecular forms, some of which suggest that post-translational processing may interfere with the catalytic activity of LAL.      

Six novel mutations in the myophosphorylase gene in patients with McArdle disease and a family with pseudo-dominant inheritance pattern

McArdle disease is an autosomal recessive glycogenosis due to deficiency of the enzyme myophosphorylase. It results from homozygous or compound heterozygous mutations in the gene for this enzyme, PYGM. We report six novel mutations in the PYGM gene based upon sequencing data including three missense mutations (p.D51G, p.P398L, and p.N648Y), one nonsense mutation (p.Y75X), one frame-shift mutation (p.Y114SfsX181), and one amino acid deletion (p.Y53del) in six patients with McArdle disease. We also report on a Caucasian family that appeared to transmit McArdle disease in an autosomal dominant manner. In order to evaluate the potential pathogenicity of the sequence variants, we performed in silico analysis using PolyPhen-2 and SIFT BLink, along with species conservation analysis using UCSC Genome Browser. The above mutations were all predicted to be disease associated with high probability and with at least the same level of certainty as several confirmed mutations. The current data add to the list of pathogenic mutations in the PYGM gene associated with McArdle disease.     

Three new adenosine deaminase mutations that define a splicing enhancer and cause severe and partial phenotypes: implications for evolution of a CpG hotspot and expression of a transduced ADA cDNA

We report three novel adenosine deaminase (ADA) mutations withinteresting implications. A Somali child with severe combinedimmunodeficiency disease (SCID) had reduced ADA mRNA in T cellsand was homozygous for the nonsense mutation Q3X. Unexpectedly,her healthy father was a compound ADA heterozygote whose secondallele carried a ‘partial’ mutation, R142Q, dueto a GA transition of a CpG dinucleotide. A CT transition ofthe same CpG produced a nonsense mutation, R142X, in two homozygousCanadian Mennonite infants with SCID. The severe and healthyphenotypes associated with R142X and R142Q, the high frequencyof ‘partial’ ADA mutations arising from CpGs inhealthy individuals of African descent and the presence of CAA(glutamine) at codon 142 in murine ADA, suggest selection forreplacement of this CpG hotspot by CpA during ADA evolution.R142X, located within a purine-rich segment at nt 62/116 ofexon 5, caused skipping of the exon, possibly by disruptinga splicing enhancer. Absence of exon 5 in T cell ADA mRNA andlow ADA activity in T cells and erythrocytes obtained at age18–22 months from one of the Mennonite children, indicatelimited expression of a normal ADA cDNA from retrovirally transducedCD34+ umbilical cordleukocytes infused shortly after birth inan attempt at stem cell gene therapy.     

Two novel nonsense mutations in <Emphasis Type="Italic">GALNT3</Emphasis> gene are responsible for familial tumoral calcinosis

Ectopic periarticular calcifications associated with elevated levels of serum phosphate represent the principal clinical features of hyperphosphatemic familial tumoral calcinosis (HFTC), a rare autosomal recessive metabolic disorder. The disease can be caused by recessive mutations in at least two different genes: GalNAc transferase 3 (GALNT3), encoding a glycosyltransferase that initiates mucin-type O-glycosylation, and fibroblast growth factor 23 (FGF23), which encodes a regulator of phosphate circulating levels. In the current study, we performed mutation analyses of the GALNT3 gene in a subject with HFTC and in his relatives. Sequence analyses revealed that the proband was a compound heterozygote for two novel nonsense mutations in exon 4 (Y322X) and in exon 7 (Q481X). Cosegregation of the mutations with the disease within the family was confirmed by polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) analysis. This is the first report describing the simultaneous presence of two different stop codons in the coding sequence of the GALNT3 gene.     

Periaxin mutation in Japanese patients with Charcot-Marie-Tooth disease

Periaxin (PRX) plays an important role in the myelination of the peripheral nerve and consequently in the pathogenesis of Charcot-Marie-Tooth disease (CMT). To date, nine nonsense or frameshift PRX mutations have been reported in eight families with CMT. The patients with PRX mutations appeared to show characteristic clinical features with early onset but slow or no progression, a common result of mutations that lead to missing a C-terminal acidic domain. Here, we report a Japanese CMT patient with these characteristic clinical features, who was a compound heterozygote for PRX R1070X and L132FsX153 mutations. We previously reported that three Japanese isolated families also had the homozygous R1070X mutation. To examine the potential founder effect of the R1070X mutation in the Japanese population, we performed haplotype analysis and found that each R1070X allele lay on a different haplotype background in these four families. Therefore, the high frequency of the R1070X mutation among the Japanese population is not likely the consequence of a founder effect, but probably a result of a mutation hot spot.     

Four novel mutations in Mucopolysaccharidosis type VII including a unique base substitution in exon 10 of the {beta}-glucuronidase gene that creates a novel 5'-splice site

Mucopolysaccharidosis type VII (MPS VII), or Sly syndrome, isa lysosomal storage disorder caused by a deficiency in the enzymeß-glucuronidase. Various clinical phenotypes of thisautosomal recessively inherited disease have been described.Recent isolation and characterization of human ß-glucuronidasecDNA and the genomic sequences facilitate analysis of moleculardefects underlying the different phenotypes, and eight mutationsin the ß-glucuronidase gene have been described. Thisreport summarizes studies characterizing four new mutationsin two Caucasian patients with a severe form of MPS VII. Threeare point mutations, resulting in two missense and one nonsensechange, and one is a 38 bp deletion. The first patient was acompound heterozygote having P148S and Y495C alleles. The secondpatient was a compound heterozygote of W507X and a 38 bp deletionat positionl642–1679 in exon 10(1642     

中国人自身免疫性多内分泌腺病综合征Ⅰ型AIRE基因突变

目的 研究一个中国自身免疫性多内分泌腺病综合征Ⅰ型(autoimmune polyendocrinopathy syndrome type Ⅰ,APS-Ⅰ)家系自身免疫调节因子(autoimmune regulator,AIRE)基因突变.方法 采用聚合酶链反应和DNA直接测序技术对该家系成员进行AIRE突变位点检测,应用限制性酶切分析的方法证实,并用生物信息学方法进行结构和功能预测.结果 患儿具有AIRE的A19T和R257X的复合杂合突变,患儿父亲仅有第1外显子的A19T突变,与本家系无亲缘关系的100名健康人不存在这一突变;患儿母亲仅有第6外显子的R257X突变.结论 发现中国APS-Ⅰ患儿存在AIRE突变,经检索人类基因突变数据库和最新文献,A19T尚未见报道,R257X尚未在亚洲人中报道.     

Identification of novel C253Y missense and Y864X nonsense mutations in the insulin receptor gene in type A insulin-resistant patients

Mutations in the insulin receptor gene have been reported in cases of type A insulin resistance. We report herein two cases of type A insulin resistance, which involve some novel mutations. Case 1 is a heterozygote of the C253Y missense mutation and case 2 is a heterozygote of the Y864X nonsense mutation. In the C253Y missense mutation in exon 3, a cysteine residue is replaced with tyrosine in the cysteine-rich domain of the alpha subunit. The Y864X in exon 13 results in a truncated receptor, which is devoid of most of the beta subunit. This mutant receptor could not be expressed on a cell membrane since the transmembrane domain is missing. Other significant mutations were not found for the entire coding regions and splice/donor sites.     

Characterisation of germline mutations in the neurofibromatosis type 1 (NF1) gene.

Neurofibromatosis type 1 is one of the most common inherited disorders with an incidence of 1 in 3000. The search for NF1 mutations has been hampered by the overall size of the gene, the large number of exons, and the high mutation rate. To date, fewer than 90 mutations have been reported to the NF1 mutation analysis consortium and the details on 76 mutations have been published. We have identified five new mutations using single strand conformation polymorphism (SSCP) and heteroduplex analysis (HA) and three intragenic deletions with the microsatellite markers. Of the five new mutations, two were in exon 27a, two in exon 45, and one in exon 49 and these include 4630delA, 4572delC, R7846X, T7828A, and one in the 3' untranslated region (3' UTR). The two nucleotide alterations in exon 27a and the one in exon 45 are predicted to produce a truncated protein.     

Glycogen storage disease type Ib: structural and mutational analysis of the microsomal glucose-6-phosphate transporter gene.

Glycogen storage disease type Ib is caused by a mutation in the gene encoding microsomal glucose-6-phosphate (G6P) transporter. We determined the exon/intron organization of the G6P transporter gene. Four overlapping genomic fragments containing the entire coding region of the gene were amplified by polymerase chain reaction (PCR) using exonic primers, and their nucleotide sequences were determined. The gene spans 4.5 kb and has eight exons. All exon/intron boundaries adhered to the canonical AG/GT rule. We then designed eight pairs of PCR primers to amplify all coding exons for a mutational analysis and studied five Japanese patients with the disease. Two novel homozygous mutations were identified in two families: a three-base deletion (delV235) in exon 2 in a consanguineous family and a splicing mutation (IVS7+1G-->T) in intron 7 in a nonconsanguineous family. Patient 3 was a compound heterozygote of W118R and IVS1+1G-->A, both of which we previously identified [Kure et al., 1998: Biochem Biophys Res Commun 248:426-431]. Patients 4 and 5 were homozygotes of W118R. Including our previous study, we found a total of ten W118R alleles in nine Japanese patients. The results support our previous suggestion that W118R is prevalent among Japanese patients. The genomic sequence data and mutation spectrum obtained from the Japanese patients will facilitate genetic diagnosis of glycogen storage disease type Ib.     

Two new mutations in a late infantile Tay-Sachs patient are both in exon 1 of the beta-hexosaminidase alpha subunit gene.

We have identified two new point mutations in the beta-hexosaminidase alpha subunit (HEX A) gene in a non-Jewish Tay-Sachs disease patient with an unusual late infantile onset disease phenotype. The patient was a compound heterozygote with each allele of the HEX A gene containing a different mutation in exon 1. One of these is a T to C transition in the initiation codon, expected to produce no alpha subunit and therefore a classical infantile phenotype. The unusual clinical aspects and later onset in the patient must therefore be a result of residual hexosaminidase A activity associated with a mutant alpha subunit containing the second mutation, substitution of serine for proline at amino acid 25 owing to a C to T change at nucleotide 73. Western blotting and DE-52 ion exchange chromatography have been used to examine the behaviour of this mutant alpha subunit.     

CFTR gene: molecular analysis in patients from South Brazil

Cystic fibrosis (CF) is the most common genetic disease among Caucasians. The CF gene, named cystic fibrosis transmembrane conductance regulator (CFTR), codifies a protein that acts as a channel through the epithelial membrane. The present work aimed (1) to detect sequence alterations in the nucleotide binding regions and at the membrane spanning domain of the CFTR gene and (2) to detect the following frequent mutations R347P, R347H, R334W, and Q359K (located in exon 7), DeltaF508 (located in exon 10), G542X, G551D, R553X, and S549N (located in exon 11), W1282X (located in exon 20), and N1303K (located in exon 21). Seventy-seven unrelated CF patients were analyzed, who were previously diagnosed and currently under treatment at the Pneumology Service of our hospital. Regions of interest were amplified by PCR using specific primers. Each sample was analyzed by a non-radioactive single-stranded conformational polymorphism (SSCP) analysis technique and restriction enzyme digestion. The DeltaF508 mutation was found in 48.7% of the alleles. Frequencies of G542X, R334W, R553X, and W1282X mutations in our population were 3.25, 1.3, 0.65, and 0.65%, respectively. No alleles were found to carry mutations G551D, R334W, R347P, R347H, Q359K, S549N, and N1303K, which were included in the screening protocol. This study allowed the characterization of 84 out of 154 CF mutant alleles (54.5%). The incidence of main CF mutations analyzed was similar to that of the south European population. Mutation data presented here will be useful for designing new DNA testing strategies for CF in South Brazil.     

Mutational analysis of the lysyl hydroxylase 1 gene (PLOD) in six unrelated patients with Ehlers-Danlos syndrome type VI: prenatal exclusion of this disorder in one family

Screening of full length cDNAs for lysyl hydroxylase 1 (LH1; also PLOD) amplified from dermal fibroblasts from six unrelated patients with the autosomal recessive disorder Ehlers-Danlos syndrome type VI (EDS VI) has shown them to be both homozygous and compound heterozygous for mutations in the gene. These mutations, which were verified in genomic DNA, result in a deficiency of LH activity (<25% of normal) in the probands, who are clinically characterized by kyphoscoliosis and extensibility of skin and joints. Four novel mutations identified in these patients include a mutation of an inserted C in one homozygous patient (1702insC) and three point mutations resulting in premature termination codons (PTCs): Y142X, Q327X (in two patients), and R670X. In the family with the R670X mutation we have prenatally excluded EDS VI by the characterization of mutations and their allelic inheritance. We have identified two previously reported mutations in the new patients: a seven exon duplication (in two patients) and a point mutation that codes for a PTC, Y511X, (in two patients). Genotype analysis indicated that the Y511X mutation may originate from a common ancestral gene. Several alternative splicing pathways have been identified which bypass the PTCs and can also restore the open reading frame.     

21-羟化酶缺乏症家系的基因突变研究

目的通过对3个21-羟化酶缺乏症家系的21-羟化酶基因(steroid21-hydroxylase gene,CYP21)直接测序研究,探讨家系中该基因突变类型。方法收集4例患者及其部分家系成员外周血,提取基因组DNA,PCR扩增CYP21基因后直接测序。结果CYP21基因序列分析共检测到6种突变类型。家系1中患者CYP21基因存在4种杂合突变:clusteE6、Q318X、A391T、P459H,其中前3种突变串联排列于同一条染色体上,P459H突变目前国内外尚未见报道,A391T为罕见突变;家系2中患者CYP21基因存在clusteE6、R483W两种杂合突变,其中R483W为罕见突变类型;家系3中患者第4外显子存在I172N纯合突变。结论在3个21-羟化酶缺乏症家系中共检测出6种突变类型,其中P459H为新发现的突变,A391T、R483W为罕见突变。虽然导致21-羟化酶缺乏症的突变主要是一些从假基因(CYP21P)转位到CYP21的序列,但随机突变也是21-羟化酶缺乏症的原因。