A pathogenic glutamate-to-aspartate substitution (D296E) in the pyruvate dehydrogenase E1 subunit gene PDHA1

In a patient with fatal neonatal lactic acidosis due to pyruvate dehydrogenase deficiency, the only potential mutation detected was c.888C>G in PDHA1, the gene for the E1alpha subunit of the complex. This would result in a substitution of glutamate for aspartate (D296E). Pathogenicity of this minor alteration in amino acid sequence was demonstrated by expression studies. By comparing the mutant sequence with the known structures of the E1 components of pyruvate dehydrogenase and the closely related branched chain alpha-ketoacid dehydrogenase, an explanation for the profound consequences of the mutation can be proposed.     

A nonsense mutation (R242X) in the branched-chain α-keto acid dehydrogenase E1α subunit gene (BCKDHA) as a cause of maple syrup urine disease

Mutation analysis of DNA from cultured amniocytes with absent branched-chain α-ketoacid dehydrogenase activity revealed a C to T transition producing a nonsense mutation (R242X) in exon 7 of the gene encoding the E1a subunit of this multienzyme complex (BCKDHA). This pregnancy occured in a large consanguinous pedigree with multiple individuals with maple syrup urine disease (MSUD). PCR amplification of the region surrounding exon 7 allowed the identification of this mutation as well as two other previously identified mutations which cause MSUD. hum Mutat 12:136, 1998. © 1998 Wiley-Liss, Inc.     

Mutations of the E1beta subunit gene (PDHB) in four families with pyruvate dehydrogenase deficiency

Pyruvate dehydrogenase complex (PDC) deficiencies are a major cause of primary lactic acidosis. Most cases result from mutations of the gene for the pyruvate dehydrogenase E1α subunit (PDHA1), with fewer cases resulting from mutations in genes for E3, E3-binding protein, E2, and the E1β subunit (PDHB). We have found four cases of PDHB mutations among 83 analyzed cases of PDC deficiency. In this series, PDHB mutations were found to be about 10% as frequent as PDHA1 mutations. All cases were diagnosed by low PDC activity, with normal E2 and E3 activities. These included a 6.5-year-old male (consanguineous, homozygous R36C); a neonatal female who died soon after birth, (compound heterozygous C306R/D319V), a 26-year-old female (heterozygous I142M/W165S), and a 13 month old female (consanguineous, homozygous Y132C) who is a sibling of a previously published case. Their ethnic background is diverse (Caucasian, Arab, and African American descent). All cases had lactic acidosis and developmental delay. Three cases had agenesis of the corpus callosum, seizures, and hypotonia; one died within the first year of life. These clinical findings are similar to those of PDHA1 deficiency, except that ataxia was more frequent in PDHA1 cases and consanguinity was found only in PDHB families. PDC activity in lymphocytes from six parents is normal, who all are heterozygous carriers for the respective mutations. Immunoreactivity of E1β was markedly reduced in one case and showed a slightly larger form of E1β in one case. Computer analysis predicts that: R36C affects the interaction of several amino acids resulting in conformational change, C306R affects interaction of the two β subunits, D319 is in the interface of E1 and E2, I142M affects conformation around a K ion affecting stability of the β subunit, W165S affects hydrophobic interaction between the β subunits, and Y132C affects interaction between the β subunits. All of these residues are conserved in E1β across species, and Y132 is also conserved in other TPP-requiring enzymes. These observations support the conclusion that these are pathogenic mutations.     

Proteinase 3 and dihydrolipoamide dehydrogenase (E3) are major autoantigens in hepatitis C virus (HCV) infection

Hepatitis C virus (HCV) infection has been found to be strikingly associated with autoimmune phenomena. The aim of the present study was to investigate the presence of various autoantibodies in patients with HCV infection. Anti-neutrophil cytoplamic antibody (ANCA), anti-dihydrolipoamide dehydrogenase (anti-E3), rheumatoid factor (RF), anti-dihydrolipoamide acetyltransferase (anti-E2), anti-SS-A/Ro (60 kD), anti-SS-A/Ro (52 kD), anti-SS-B/La, anti-topoisomerase II (anti-topo II), anti-cardiolipin (aCL), anti-dsDNA, anti-ssDNA, anti-nuclear antibodies (ANA), anti-proteinase 3 (anti-Pr3) and anti-myeloperoxidase (anti-MPO) were determined in sera from 516 patients with HCV infection, 11 with primary biliary cirrhosis (PBC) and 44 healthy controls. Assays employed were indirect immunofluoresence, the particle latex agglutination test, enzyme-linked immunosorbent assay (ELISA) and immunoblotting. ANCA, anti-E3 antibody and RF were positive in 278/516 (55.6%), 276/516 (53.3%) and 288/516 (56%) patients with HCV infection, respectively. Positivity for ANA was present in 15.8%, anti-ssDNA in 15.6%, anti-dsDNA in 8.5%, aCL in 5%, anti-SS-B/La in 4.1%, anti-SS-A/Ro (60 kD) in 3.9%, anti-E2 in 3.3% and anti-SSA/Ro (52 kD) in 1.2%, anti-MPO in 4.8%, anti-Topo II and anti-actinin in 0%. All sera with ANCA showed c-ANCA patterns and contained anti-PR3 specificity. HCV patients with ANCA showed a higher prevalence of skin involvement, anaemia, abnormal liver function and alpha-Fetoprotein (alpha-FP). HCV patients with anti-E3 antibodies showed a higher prevalence of liver cirrhosis, arthritis, abnormal liver function and elevated alpha-FP levels. The prevalence of autoantibodies was not affected by treatment with interferon-alpha (IFN-alpha). In conclusion, autoantibodies are commonly found in patients with HCV infection. There is a high prevalence of anti-E3, ANCA and RF in these patients. Proteinase 3 and E3 are the major target antigens in HCV infection. HCV may be regarded as a possible causative factor in ANCA-related vasculitis.     

Arginine 302 mutations in the pyruvate dehydrogenase E1α subunit gene: Identification of further patients and in vitro demonstration of pathogenicity

Three further patients with mutations in the codon for arginine 302 of the E1α subunit of the pyruvate dehydrogenase complex have been identified. Mutations in this codon have now been found in nine patients with pyruvate dehydrogenase deficiency in seven unrelated families, in sharp contrast to the great majority of other PDH E1α mutations which have been described in single individuals only. Because of the relatively high frequency of this mutation and because very few PDH E1α mutations have been demonstrated to be causative, we have established a system for analysing the consequences of defined mutations using transfection of normal and mutant PDH E1α cDNA into transformed human fibroblasts which have no endogenous E1α mRNA or protein. Using this test system, we have demonstrated that the R302C mutation results in the production of PDH E1α protein which is devoid of enzymic activity. Hum Mutat 12:114–121, 1998. © 1998 Wiley-Liss, Inc.     

一个琥珀酸半醛脱氢酶缺陷病家系ALDH5A1基因突变分析

目的 对1例临床怀疑且经尿筛查诊断为琥珀酸半醛脱氢酶缺陷病的患儿及家系进行ALDH5A1基因突变分析,以进一步明确诊断和辅助遗传咨询.方法 应用聚合酶链反应及DNA直接测序技术对1例琥珀酸半醛脱氢酶缺陷病患儿及其父母的ALDH5A1基因进行突变位点检测,同时检测100名健康对照者的ALDH5A1基因以排除多态性变异.结果 患儿携带有ALDH5A1基因编码区序列第3外显子c.527G＞A(p.Gly176Glu)和第4外显子c.691G＞A(p.Glu231Lys)两种杂合突变,其母亲为c.527G＞A杂合突变携带者,父亲为c.691G＞A杂合突变携带者.另外患儿还存在两种已报道的核酸多态性改变:c.545C＞T杂合突变和c.538C＞T纯合突变.患儿的c.545C＞T突变来源于父亲,c.538C＞T突变分别来源于父母.100名健康对照者中未检测到c.527G＞A和c.691G＞A突变.结论 c.527G＞A(p.Gly176Glu)和c.691G＞A(p.Glu231 Lys)错义突变可能是该患儿的致病突变.     

Long-chain 3-hydroxyacyl-Coenzyme A dehydrogenase (L-CHAD) deficiency in a patient with the Bannayan-Riley-Ruvalcaba syndrome

Bannayan-Riley-Ruvalcaba syndrome (BRRS) is an autosomal dominant condition of macrocephaly in combination with lipomas/hemangiomas, hypotonia, developmental delay, and a lipid myopathy. The etiology of the lipid storage myopathy has been unclear. We describe a black boy with findings of BRRS who also has a defect in long-chain fatty acid oxidation expressed in cultured skin fibroblasts as a deficiency of long-chain-L-3-hydroxyacyl-CoA dehydrogenase (L-CHAD). He also has an abnormal brain MRI and increased size of both lower limbs. We present this child because of his unusual combination of findings, and postulate that L-CHAD deficiency may be the cause of the lipid myopathy in BRRS. © 1994 Wiley-Liss, Inc.     

A founder mutation underlies a severe form of phosphoglutamase 3 (PGM3) deficiency in Tunisian patients

Phosphoglucomutase 3 (PGM3) protein catalyzes the conversion of N-acetyl-d-glucosamine-6-phosphate (GlcNAc-6-P) to N-acetyl-d-glucosamine-1-phosphate (GlcNAc-1-P), which is required for the synthesis of uridine diphosphate N-acetylglucosamine (UDP-GlcNAc) an important precursor for protein glycosylation. Mutations in PGM3 gene have been recently shown to underlie a new congenital disorder of glycosylation often associated to elevated IgE. Herein, we report twelve PGM3 deficient patients. They belong to three highly consanguineous families, originating from a rural district in the west central Tunisia. The patient’s clinical phenotype is characterized by severe respiratory and cutaneous infections as well as developmental delay and severe mental retardation. Fourteen patients died in early infancy before diagnosis supporting the severity of the clinical phenotype.Laboratory findings revealed elevated IgE, CD4 lymphopenia and impaired T cell proliferation in most patients. Genetic analysis showed the presence, of a unique homozygous mutation (p.Glu340del) in PGM3 gene leading to reduced PGM3 abundance. Segregating analysis using fifteen polymorphic markers overlapping PGM3 gene showed that all patients inherited a common homozygous haplotype encompassing 10-Mb on chromosome 6. The founder mutational event was estimated to have occurred approximately 100 years ago.To date, (p.Glu340del) mutation represents the first founder mutation identified in PGM3 gene. These findings will facilitate the development of preventive approaches through genetic counselling and prenatal diagnosis in the affected families.     

海南汉族、黎族人葡萄糖-6-磷酸脱氢酶缺乏症的基因突变型分析及一种新的G6PD基因突变型的鉴定

目的 阐明海南汉族、黎族人群中葡萄糖－6－磷酸脱氢酶缺乏症的分子基础。方法 用聚合酶链反应、限制性内切酶消化筛查了1388G→A、1360C→T、1024C→T、517T→C、493A→G、487G→A、392G→T和95A→G突变。用单链构象多态性分析筛查其它突变;用核苷酸顺序分析鉴定具有SSCP异常区带样品的突变;。结果 在59例汉族G6PD缺乏症患者中,发现1388G→A14例（23．7％）、871G→A3例（5．1％）、835A→T1例（1．7％）517T→C1例（1．7％）、392G→T3例（5．1％）95A→G4例（6．8％）;在32例黎族G6PD缺乏症患者中,发现1388G→A6例（18．8％）、871G→A3例（9．4％）和95A→G2例（6．3％）;在1例汉族患者中发现了一种新的G6PD基因突变－835A→G突变,此突变导致第279位的苏氨酸被丙氨酸取代,将此突变型命名为G6PD－海口,其酶活性约是正常的10％,此835A→T突变的活性低,后者的酶活性约是正常的40％。分析人G6PD的三维结构模型表明,第279位苏氨酸残基的羟基是维持G6PD亚基相互作用的基团。结论 海南汉族、黎族人群中具有共同的常见G6PD基因突变型;与中国其它地区人群的G6PD基因突变谱比较,结果表明某些G6PD基因突变广泛分布于中国南方不同地区人群中;G6PD第279位苏氨酸残基的可能是维持G6PD亚基相互作用及酶活性的必需基团。     

A novel splice-site mutation in the common gamma chain (gammac) gene IL2RG results in X-linked severe combined immunodeficiency with an atypical NK+ phenotype

Mutations in the gene encoding the common gamma chain (gammac) of interleukin receptors 2, 4, 7, 9, 15 and 21 result in X-linked severe combined immunodeficiency (SCID-X1). Classically, this disease is characterised by an absence of T and NK cells, and near normal numbers of functionally deficient B cells (B(+), T(-), NK(-) phenotype). Atypical phenotypes have also been described, but relatively little is known about the mechanisms by which the underlying mutations impair gammac-dependent interleukin receptor signalling to produce these disease variants. Here we describe a novel splice-site mutation resulting in the presence of near normal numbers of functionally deficient NK cells (B(+), T(-), NK(+) phenotype), in a SCID-X1 infant who was subsequently treated by gene therapy. The mutation, c.468+3A>C affecting the third base of intron 3 in the IL2RG gene, was shown to result in the production of two aberrantly spliced gammac mRNA species and reduction of correctly spliced message to trace levels, consistent with failure to detect gammac on the surface of B and NK cells by FACS analysis. The infant's genotype-phenotype correlation supports the hypothesis that interleukin 15 receptor-mediated signalling is preferentially retained as the amount of cell surface gammac becomes limiting. The possible implications for immunological reconstitution following gene therapy are also discussed.     

Vitamin E deficiency ataxia with (744 del A) mutation on alpha-TTP gene: genetic and clinical peculiarities in Moroccan patients

Ataxia with vitamin E deficiency (AVED) is an autosomal recessive disease characterized clinically by neurological symptoms with often striking resemblance to those of Friedreich's ataxia (FA). Molecular analysis is needed for an early differential diagnosis, in order to initiate therapeutic vitamin E supplementation before damage develops. We studied 16 patients from seven Moroccan families presenting an autosomal recessive Friedreich-like ataxia with vitamin E deficiency. Our patients were homozygous for 744 del A mutation of alpha-TTP gene. Compilation of clinical records revealed a great phenotypic variability and some features indicating a new possible role of vitamin E in hypothalamo-hypophysial system regulation and cardiomyopathy prevention. Early vitamin E supplementation may provide considerable improvement of neurological signs and other associated abnormalities. Clinical heterogeneity is for involvement of other non-genetic defect and indicated another role of vitamin E, which should be better studied.     

A novel frameshift mutation (141delT) in exon 1 of the 21‐hydroxylase gene (CYP21) in a patient with the salt wasting form of congenital adrenal hyperplasia

Congenital adrenal hyperplasia (CAH) is a common autosomal recessive disease with a wide range of clinical manifestation. In 90‐95% of the cases it is caused by 21‐hydroxylase deficiency (OMIM #201910) due to mutations of the CYP21 gene (GDB Accession #M12792). In most cases the CYP21‐inactivating point mutations are transferred by apparent gene conversions from CYP21P to CYP21. In only a few cases point mutations have been described, which are not present in the pseudogene. Using Southern blot analysis and DNA sequencing we have identified a novel mutation (141delT) of the CYP21 gene in a patient suffering from the salt wasting form of CAH. This results in a premature termination of a truncated protein at amino acid position 51 (L51X), which is likely to result in an enzyme with no activity. This novel mutation has not been reported to occur in the CYP21P alleles and it was not found in the CYP21P alleles in this CAH family. Hum Mutat 14:90–91, 1999. © 1999 Wiley‐Liss, Inc.     

A novel nonsense mutation of the PEPD gene in a Japanese patient with prolidase deficiency

A nonsense mutation at amino acid residue 184 in the human peptidase D (PEPD) gene caused the production of a truncated polypeptide. Characterizing molecular defects in patients provides clues to elucidate the relationship between the phenotype and the genotype. Received: November 8, 1999 / Accepted: November 24, 1999     

A Korean female patient with thiamine-responsive pyruvate dehydrogenase complex deficiency due to a novel point mutation (Y161C)in the PDHA1 gene

Pyruvate dehydrogenase complex (PDHC) deficiency is mostly due to mutations in the X-linked E1alpha subunit gene (PDHA1). Some of the patients with PDHC deficiency showed clinical improvements with thiamine treatment. We report the results of biochemical and molecular analysis in a female patient with lactic acidemia. The PDHC activity was assayed at different concentrations of thiamine pyrophosphate (TPP). The PDHC activity showed null activity at low TPP concentration (1 x 10(-3) mM), but significantly increased at a high TPP concentration (1 mM). Sequencing analysis of PDHA1 gene of the patient revealed a substitution of cysteine for tyrosine at position 161 (Y161C). Thiamine treatment resulted in reduction of the patient's serum lactate concentration and dramatic clinical improvement. Biochemical, molecular, and clinical data suggest that this patient has a thiamine-responsive PDHC deficiency due to a novel mutation, Y161C. Therefore, to detect the thiamine responsiveness it is necessary to measure activities of PDHC not only at high but also at low concentration of TPP.     

Novel mutations in 3‐phosphoglycerate dehydrogenase (PHGDH) are distributed throughout the protein and result in altered enzyme kinetics

Three‐phosphoglycerate dehydrogenase (3‐PGDH) deficiency is a rare recessive inborn error in the biosynthesis of the amino acid L‐serine characterized clinically by congenital microcephaly, psychomotor retardation, and intractable seizures. The biochemical abnormalities associated with this disorder are low concentrations of L‐serine, D‐serine, and glycine in cerebrospinal fluid (CSF). Only two missense mutations (p.V425M and p.V490M) have been identified in PHGDH, the gene encoding 3‐PGDH, but it is currently unclear how these mutations in the carboxy‐terminal regulatory domain of the protein affect enzyme function. We now describe five novel mutations in five patients with 3‐PGDH deficiency; one frameshift mutation (p.G238fsX), and four missense mutations (p.R135W, p.V261M, p.A373T, and p.G377S). The missense mutations were located in the nucleotide binding and regulatory domains of 3‐PGDH and did not affect steady‐state expression, protein stability, and protein degradation rates. Patients' fibroblasts displayed a significant, but incomplete, reduction in maximal enzyme activities associated with all missense mutations. In transient overexpression studies in HEK293T cells, the p.A373T, p.V425M, and p.V490M mutations resulted in almost undetectable enzyme activities. Molecular modeling of the p.R135W and p.V261M mutations onto the partial crystal structure of 3‐PGDH predicted that these mutations affect substrate and cofactor binding. This prediction was confirmed by the results of kinetic measurements in fibroblasts and transiently transfected HEK293T cells, which revealed a markedly decreased V_max and an increase in K_m values, respectively. Taken together, these data suggest that missense mutations associated with 3‐PGDH deficiency either primarily affect substrate binding or result in very low residual enzymatic activity. Hum Mutat 0, 1–8, 2009. © 2009 Wiley‐Liss, Inc.     

Expanding the clinical spectrum of mitochondrial 3‐hydroxy‐3‐methylglutaryl‐CoA synthase deficiency with Turkish cases harboring novel HMGCS2 gene mutations and literature review

Mitochondrial 3‐hydroxy‐3‐methylglutaryl‐CoA synthase (mHS) deficiency is a very rare autosomal recessive inborn error of ketone body synthesis and presents with hypoketotic hypoglycemia, metabolic acidosis, lethargy, encephalopathy, and hepatomegaly with fatty liver precipitated by catabolic stress. We report acute presentation of two patients from unrelated two families with novel homozygous c.862C>T and c.725‐2A>C mutations, respectively, in HMGCS2 gene. Affected patients had severe hypoketotic hypoglycemia, lethargy, encephalopathy, severe metabolic and lactic acidosis and hepatomegaly after infections. Surprisingly, molecular screening of the second family showed more affected patients without clinical findings. These cases expand the clinic spectrum of this extremely rare disease.