Pyruvate Dehydrogenase E1 Alpha Research Articles

Pyruvate dehydrogenase complex deficiency with multiple minor anomalies

Pyruvate dehydrogenase complex (PDHC) deficiency is known to cause congenital lactic acidosis. The case of a 9-month-old female infant with PDHC deficiency caused by a mutation in exon 11 of the pyruvate dehydrogenase (PDH) E1 alpha gene is described. Her facial features were as follows: frontal bossing, upslanting palpebral fissures, a short upturned nose, a long philtrum and low set ears. These anomalies are characteristic not only of a malformation syndrome or chromosomal aberration, but also of PDHC deficiency. Because PDHC deficiency requires early treatment, metabolic disorders should be kept in mind in a patient with dysmorphic features. Further, she had multiple minor anomalies including bilateral inguinal herniae, an umbilical hernia and small hands and feet, which have not been described in previous reports.

Mitochondrial and nuclear genes present conflicting portraits of human origins.

Human mitochondrial DNA (mtDNA) sequences reveal an abundance of polymorphic sites in which the frequencies of the segregating bases are very different. A typical polymorphism involves one base at low frequency and the other base at high frequency. In contrast, nuclear gene data sets tend to show an excess of polymorphisms in which both segregating bases are at intermediate frequencies. A new statistical test of this difference finds significant differences between mtDNA and nuclear gene data sets reported in the literature. However, differences in the polymorphism patterns could be caused by different sample origins for the different data sets. To examine the mtDNA-nuclear difference more closely, DNA sequences were generated from a portion of the X-linked pyruvate dehydrogenase E1 alpha subunit (PDHA1) locus and from a portion of mitochondrial control region I (CRI) from each of eight individuals, four from sub-Saharan Africa. The two genes revealed a significant difference in the site frequency distribution of polymorphic sites. PDHA1 revealed an excess of intermediate-frequency polymorphisms, while CRI showed an excess of sites with the low-high frequency pattern. The discrepancy suggests that mitochondrial variation has been shaped by natural selection, and may not be ideal for some questions on human origins.

Refined localization of the pyruvate dehydrogenase E1 alpha gene (PDHA1) by linkage analysis.

Pyruvate dehydrogenase (PDH) E1 alpha is a key component in the PDH complex which catalyzes the oxidative decarboxylation of pyruvate to acetyl-CoA. Defects in the gene coding for PDH E1 alpha (PDHA1) are associated with a variety of clinical symptoms, often of a severe character. In the present study, the segregation of three polymorphic CA repeats located in PDHA1 was followed in the 40 CEPH reference pedigrees. Using these data, multipoint linkage analysis was carried out, refining the genetic location of PDHA1. The 16-point map presented locates PDHA1 in an approximately 3-cM interval between DXS999 and DXS365 with odds of more than 1000:1. From known physical localizations of the flanking marker loci, PDHA1 could be regionally assigned to Xp22.1-p22.2. The information provided should be of value in clinical settings.

DNA diagnosis of pyruvate dehydrogenase deficiency in female patients with congenital lactic acidaemia.

The diagnosis of pyruvate dehydrogenase (PDH) E1 alpha deficiency, which is an X-linked inborn error of metabolism, is usually established by the measurement of PDH complex activity in cultured cells. However, heterozygous female patients with PDH E1 alpha deficiency may be misdiagnosed when the normal X chromosome is predominantly expressed in the cultured cells. Therefore, in female patients with convincing clinical presentations of PDH E1 alpha deficiency and the normal enzyme activity, the X-inactivation pattern should be analysed and the PDH E1 alpha gene screened for mutations. For this screening, we applied the method of single-strand conformational polymorphism (SSCP) and DNA sequencing and examined 11 female patients with congenital lactic acidaemia whose PDH complex activity was normal in cultured cells. In 2 of the 11 female patients, we found distinct pathogenic missense mutations in the PDH E1 alpha gene (G89S and G291R). Both affected patients showed a similar clinical presentation and had been diagnosed as West syndrome. In 3 of the 11 patients, we found a polymorphic base-pair substitution in exon 9 of the PDH E1 alpha gene which resulted in a changed amino acid residue (M282L). We conclude that PCR-SSCP analysis of the PDH E1 alpha gene, followed by DNA sequencing, is a useful method to screen for mutations of the PDH E1 alpha gene in female patients with congenital lactic acidaemia who have normal enzyme activities in available samples, normal ratio of lactate to pyruvate, and predominantly raised lactate concentration in cerebrospinal fluid.

Severe brain malformations in previously undescribed 4-nucleotide deletion in exon 10 of pyruvate dehydrogenase E1-alpha gene

Severe brain malformations in previously undescribed 4-nucleotide deletion in exon 10 of pyruvate dehydrogenase E1-alpha gene

Differential Expression of Two Testis-Specific Transcripts of the Mouse Pdha-2 Gene During Spermatogenesis

Analysis of the expression of the testis-specific isoform of the mouse pyruvate dehydrogenase E1 alpha subunit gene (Pdha-2) during various stages of spermatogenesis has shown that a 2.0-kb Pdha-2 mRNA is initially transcribed in meiotic prophase. The initial appearance of Pdha-2 mRNA precedes that of Pgk-2 and corresponds to the appearance of Ldh-3 mRNA. A second Pdha-2 1.7-kb transcript is present in post-meiotic round spermatids. Polysomal analysis of purified spermatogenic cell populations demonstrates that the 2.0-kb mRNA species is translated in diploid, pachytene spermatocytes and the 1.7-kb mRNA species is translated in round spermatids, although a large proportion is present on the nonpolysomal fraction and may be stored for use in later stages of spermiogenesis.

A four-nucleotide insertion hotspot in the X chromosome located pyruvate dehydrogenase E1 alpha gene (PDHA1).

A four-nucleotide insertion hotspot in the X chromosome located pyruvate dehydrogenase E1 alpha gene (PDHA1).

Pyruvate dehydrogenase E1 alpha deficiency.

Pyruvate dehydrogenase (PDH) deficiency has long been recognized as the most common defined cause of primary lactic acidosis in infancy and early childhood. More recently, it has also been described in patients with subacute/chronic neurodegenerative disease without significant metabolic acidosis. The great majority of cases of PDH deficiency result from a genetic defect in the E1 alpha subunit of the complex. PDH E1 alpha deficiency is an X-linked inborn error of metabolism in which a high proportion of heterozygous females manifest the condition. In this review of 29 patients with PDH E1 alpha deficiency, particular emphasis is given to those aspects of the disorder which are specifically related to the X chromosome location of the PDH E1 alpha gene. These include the broad spectrum of clinical presentations and problems of diagnosis, especially antenatal diagnosis, in females.

Transcriptional expression of a testis-specific variant of the mouse pyruvate dehydrogenase E1 alpha subunit.

An isogene of the E1 alpha subunit of the mouse pyruvate dehydrogenase complex was shown in a previous study to map to chromosome 19. Here we demonstrate using Northern blot analysis that this gene is expressed in a testis-specific fashion. Two testis-specific E1 alpha transcripts were detected: (1) a 2.0-kb transcript that is abundant in pachytene cells but also detectable during earlier stages of spermatogenesis, and (2) a shorter 1.7-kb transcript detectable only in round spermatids. Analysis of both transcripts following RNase H digestion revealed that the smaller message is not derived from the shortening of the poly(A) tail and most likely results from the alternate use of two polyadenylation signals. Finally, analysis of polysomes isolated from 20- and 80-day-old mouse testes demonstrated that the 2.0-kb transcript is associated with the polysomal fraction, suggesting that this message is transcribed and actively translated at the same time. We conclude from these results that expression of the testis-specific E1 alpha is initially expressed during the meiotic prophase stage of spermatogenesis and not under any apparent post-transcriptional regulation.

A flow cytometric method to detect anti-pyruvate dehydrogenase antibody in primary biliary cirrhosis.

Primary biliary cirrhosis (PBC) is an autoimmune disease characterized by the presence of anti-mitochondrial antibodies specifically directed against the M2 group of mitochondrial antigens. Recently, the E-1, the E-2, and protein X components of pyruvate dehydrogenase enzyme complex have been identified as the major antigens within the M2 group of autoantigens. An immunoassay using pyruvate dehydrogenase enzyme complex as a specific antigen for the diagnosis of PBC was developed. Pyruvate dehydrogenase enzyme complex was attached to polystyrene microbeads, incubated with sera from PBC patients (n = 18), normal controls (n = 50), or patients with other autoimmune diseases (n = 26), followed by incubation with a second fluorescein isothiocyanate conjugated goat anti-human immunoglobulin and then analyzed by flow cytometry. High numbers of fluorescence channels (mean, 1,693 +/- 846) were obtained for all PBC sera except for two patients. Compared to the conventional anti-mitochondrial antibody assay, the assay had a sensitivity rate of 94% and a specificity rate of 100%. The reactive antibodies are predominantly of the immunoglobulin G3 subclass. Their levels could be correlated with the histopathologic stages of PBC. These results were corroborated by immunoblotting. Sera from patients with later stages of PBC strongly reacted with pyruvate dehydrogenase enzyme complex components, E1 alpha, and protein X.

Mutations and polymorphisms in the pyruvate dehydrogenase E1 alpha gene.

We present an update on mutations and polymorphisms in the human X chromosome located pyruvate dehydrogenase E1 alpha gene. A total of 20 different mutations are tabulated. The mutations include deletions, insertions, and point mutations. Certain sequences seem particularly prone to mutation. Most of the mutations are found in exons 10 and 11. Furthermore, four of the mutations are seen in unrelated patients. Little is known about how the mutations affect the structure or function of the pyruvate dehydrogenase complex.

Pyruvate dehydrogenase and pyruvate carboxylase. Sites of pretranslational regulation by glucose of glucose-induced insulin release in pancreatic islets.

It has been shown previously that glucose-induced insulin release is completely absent in rat pancreatic islets that had been cultured for 1 day at low glucose (1 mM) and that it is restored by culturing islets for a 2nd day at high (20 mM) glucose (MacDonald, M. J., Fahien, L. A., McKenzie, D. I., and Moran, S. M. (1991) Am. J. Physiol. 259, E548-E554). It has been suggested that the incapacitation of glucose's insulinotropism is due to down-regulation of the synthesis of enzymes that process glucose's metabolic signal for insulin release. In the current study, results of metabolic, enzymic, and molecular biologic experiments were each consistent with (an) intramitochondrial site(s) of down-regulation in islets cultured at low glucose. Glucose metabolism was inhibited 80% in islets cultured at 1 mM glucose. The suppression of release of 14CO2 from [6-14C]glucose greater than from [U-14C]glucose greater than [3,4-14C]glucose greater than from [1-14C]glucose in islets cultured at low glucose indicated a mitochondrial site of down-regulation because C-6 of glucose can only be converted to CO2 in the citric acid cycle, whereas C-1 can be released as CO2 in the 6-phosphogluconate dehydrogenase [corrected] reaction, and C-6 of glucose dwells in the citric acid cycle longer than carbons 2-5 of glucose. Since carbons 3 and 4 of glucose can be decarboxylated in the pyruvate dehydrogenase reaction, incomplete suppression of CO2 formation from these carbons is consistent with suppression of pyruvate carboxylation as well as decarboxylation. Formation of 3HOH from [5-3H]glucose was equal in the two groups of islets, indicating that glycolysis as far as phosphoenolpyruvate was intact. This idea was supported by assays which showed that activities of enzymes of the glycolytic pathway between glucokinase/hexokinase and pyruvate kinase were equal in both types of islets. Additional studies indicated that regulation by glucose was at transcription of genes coding for some mitochondrial enzymes. Glucokinase, malic enzyme, and fumarase mRNAs were not affected by glucose, whereas the pyruvate dehydrogenase E1 alpha subunit and pyruvate carboxylase mRNAs were decreased 85-90% in islets cultured at 1 mM glucose. Pyruvate dehydrogenase enzyme activity was decreased to a similar extent in these islets. About 24 h was required for maximal (de)induction of pyruvate dehydrogenase E1 alpha and pyruvate carboxylase mRNAs, and the amounts of transcripts were proportional to the concentrations of glucose between 1 and 20 mM.(ABSTRACT TRUNCATED AT 400 WORDS)

Polymorphisms in the human X-linked pyruvate dehydrogenase E1? gene

Pyruvate dehydrogenase E1 alpha deficiency is an X-chromosome-linked disorder, often with fatal consequences. We have searched for genetically useful polymorphisms in or near this gene. No restriction fragment length polymorphisms were detected using a battery of 36 different restriction enzymes and probing with a full-length cDNA fragment, or two single-copy genomic fragments located within intron 8, and 15 kb 3' of the coding region, respectively. The chemical cleavage method was then applied to the detection of base changes in or near the gene. One polymorphism was found in exon 8 of the coding region. However, no base changes were detected in intron 3 or in the part of intron 8 covered by fragment gB2. Three blocks of microsatellite DNA containing variable numbers of CA-repeats were isolated from the 5' end of the gene and characterized. Length polymorphisms in these microsatellite DNAs were analysed using the polymerase chain reaction. Although the three loci are tightly linked, the polymorphisms appear not to be in disequilibrium, making them useful markers in linkage studies of the pyruvate dehydrogenase E1 alpha gene. Of 31 females analysed 12(39%) were heterozygous for at least one length polymorphism of the three (CA)n alleles.

Characterization of the mutations in three patients with pyruvate dehydrogenase E1α deficiency

The human pyruvate dehydrogenase complex catalyses the oxidative decarboxylation of pyruvate to acetyl-CoA. Defects in several of the seven subunits have been reported, but the majority of mutations affect the E1 component and especially the E1 alpha subunit. However, the clinical presentation of patients with pyruvate dehydrogenase E1 alpha deficiency is extremely variable. Dependency of the brain on pyruvate dehydrogenase activity and localization of the gene for the somatic form of the pyruvate dehydrogenase E1 alpha subunit to the X chromosome provide the basis for a better understanding of the variation in the clinical manifestations. Further understanding of the function and interaction of subunits and the pathophysiology of pyruvate dehydrogenase deficiency necessitates the characterization of mutations in the pyruvate dehydrogenase complex. We report the analysis of three patients with pyruvate dehydrogenase E1 alpha deficiency. One female has a three base pair deletion which affects dephosphorylation of the subunit. Of two males analysed, one has a two base pair deletion causing a shift in the reading frame. The other has a base change, resulting in an Arg to His substitution. All three mutations are located near the carboxyl terminus of the subunit.

Pyruvate dehydrogenase E1? subunit genes in the mouse: Mapping and comparison with human homologs

Two gene loci for the E1 alpha subunit of the pyruvate dehydrogenase (PDH) complex have been mapped in the mouse by in situ hybridization. One locus maps to the X chromosome in the region F3-F4, the other to chromosome 19, in band B close to the centromere. This arrangement is exactly comparable to the situation in man where there is an X-linked PDH E1 alpha locus and an autosomal locus on chromosome 4. Comparison of the regional localization of the human and mouse X-linked PDH E1 alpha genes provides further information concerning sites of rearrangement of segments of the X chromosome during mammalian evolution. The human autosomal PDH E1 alpha gene is a "processed" gene, which lacks the introns that are present in the X-linked gene. It codes for a testis-specific E1 alpha subunit that is only expressed after the onset of spermatogenesis. The comparative mapping results in the mouse suggest that the genetic organization and pattern of expression of the two PDH E1 alpha genes is the same in the two species.

Characterization of two cDNA clones for pyruvate dehydrogenase E1 beta subunit and its regulation in tricarboxylic acid cycle-deficient fibroblast.

Two distinct types of cDNA clones encoding for the pyruvate dehydrogenase (PDH) E1 beta subunit were isolated from a human liver lambda gt11 cDNA library and characterized. These cDNA clones have identical nucleotide sequences for PDH E1 beta protein coding region but differ in their lengths and in the sequences of their 3'-untranslated regions. The smaller cDNA had an unusual polyadenylation signal within its protein coding region. The cDNA-deduced protein of PDH E1 beta subunit revealed a precursor protein of 359 amino acid residues (Mr 39,223) and a mature protein of 329 residues (Mr 35,894), respectively. Both cDNAs shared high amino acid sequence similarity with that isolated from human foreskin (Koike, K.K., Ohta, S., Urata, Y., Kagawa, Y., and Koike, M. (1988) Proc. Natl. Acad. Sci. U.S.A. 85, 41-45) except for three regions of frameshift mutation. These changes led to dramatic alterations in the local net charges and predicted protein conformation. One of the different sequences in the protein coding region of liver cDNA (nucleotide position 452-752) reported here was confirmed by sequencing the region after amplification of cDNA prepared from human skin fibroblasts by the polymerase chain reaction. Southern blot analysis verified simple patterns of hybridization with E1 beta cDNA, indicating that the PDH E1 beta subunit gene is not a member of a multigene family. The mechanisms of differential expression of the PDH E1 alpha and E1 beta subunits were also studied in established fibroblast cell lines obtained from patients with Leigh's syndrome and other forms of congenital lactic acidosis. In Northern blot analyses for PDH E1 alpha and E1 beta subunits, no apparent differences were observed between two Leigh's syndrome and the control fibroblasts studied: one species of PDH E1 alpha mRNA and three species of E1 beta mRNA were observed in all the cell lines examined. However, in one tricarboxylic acid cycle deficient fibroblast cell line, which has one-tenth of the normal enzyme activity, the levels of immunoreactive PDH E1 alpha and E1 beta subunits were markedly decreased as assessed by immunoblot analyses. These data indicated a regulatory mutation caused by either inefficient translation of E1 alpha and E1 beta mRNAs into protein or rapid degradation of both subunits upon translation. In contrast, the PDH E1 alpha and E1 beta subunits in two fibroblast cell lines from Leigh's syndrome patients appeared to be normal as judged by 1) enzyme activity, 2) mRNA Northern blot, 3) genomic DNA Southern blot, and 4) immunoblot analyses indicating that the lactic acidosis seen in these patients did not result from a single defect in either of these E1 alpha and E1 beta subunits of the PDH complex.

Mutation of the 97‐197‐197‐1subunit of the pyruvate dehydrogenase complex, in relation to heterogeneity

Pyruvate dehydrogenase complex was studied using bio- and immunochemical methods in cultured cells derived from two patients with the severe type and one patient with the mild type of pyruvate dehydrogenase complex deficiency. In patients 1 and 2, enzyme activity was all but undetectable and associated with the absence of E1 alpha subunit of the complex. Patient 3 had a slightly reduced level of enzyme activity, and this was associated with a larger form of E1 alpha subunit. The amount and size of E1 alpha mRNA in the three patients was similar to that of control samples. Thus, the severity of E1 alpha deficiency in these three patients is likely to depend on the type of mutation in the pyruvate dehydrogenase E1 alpha subunit and the synthesis and degradation rate of the subunit.

The human pyruvate dehydrogenase complex. Isolation of cDNA clones for the E1 alpha subunit, sequence analysis, and characterization of the mRNA.

cDNA clones corresponding to the entire length of mRNA for the alpha subunit of human pyruvate dehydrogenase (EC 1.2.4.1), the E1 component of the pyruvate dehydrogenase complex, have been isolated from liver cDNA libraries. Two classes of cDNA clones were obtained and these correspond to two forms of pyruvate dehydrogenase E1 alpha mRNA. Both mRNA species have been demonstrated in a variety of human tissues and cultured fibroblasts. The cDNA sequence has been determined and, from it, the protein sequence of the human E1 alpha subunit was deduced. The protein is synthesized with a typical mitochondrial import leader sequence and the peptide bond at which this sequence is cleaved after transport into the mitochondrion has been determined by direct amino acid sequencing of the mature E1 alpha subunit. The human pyruvate dehydrogenase E1 alpha subunit contains identical phosphorylation sites to those found in the corresponding porcine protein. Preliminary studies of pyruvate dehydrogenase E1 alpha mRNA in cultured fibroblasts from patients with severe pyruvate dehydrogenase deficiency have revealed considerable heterogeneity as would be expected from protein studies.