Pyruvate Dehydrogenase E1 Alpha Deficiency Research Articles

Clinical manifestations in two patients with pyruvate dehydrogenase deficiency and long-term survival

Pyruvate dehydrogenase E1-alpha deficiency (PDHAD) results in lactic acidosis and hyperpyruvatemia. Two patients with PDHAD, a man with a p.R263Q mutation, and a girl with a p.C145del mutation in PDHE1α, presented with lactic acidosis with neurological disorder. These patients were able to survive for a long period under careful nursing care. Herein, we discuss the factors contributing to their relatively stable clinical course, albeit with intellectual disability.

MRI Features of 4 Female Patients With Pyruvate Dehydrogenase E1 alpha Deficiency

Pyruvate dehydrogenase complex is a key intramitochondrial multienzyme complex required for the conversion of pyruvate to acetyl-CoA. Most patients with pyruvate dehydrogenase deficiency have a defect in the E1 alpha subunit, associated with mutations in the PDHA1 gene. In this report, we submit detailed magnetic resonance images in 4 affected female patients with PDHA1 mutations who had with severe cortical atrophy, dilated ventricles, and an incomplete corpus callosum. In one of these patients, the magnetic resonance imaging pattern prompted molecular diagnostic testing when enzymatic testing was normal. We underscore that this constellation of features, which may be misdiagnosed as periventricular leukomalacia, illustrates a pattern highly suggestive of a deficiency of pyruvate dehydrogenase E1 alpha in female patients and should trigger appropriate diagnostic investigations.

Gene therapy for pyruvate dehydrogenase E1alpha deficiency using recombinant adeno-associated virus 2 (rAAV2) vectors.

To determine the feasibility of gene transfer to correct defects in the E1alpha subunit of the pyruvate dehydrogenase (PDH) complex (PDC), we constructed rAAV vectors that expressed PDH E1alpha, either alone or with a green fluorescent protein tag, from a hybrid cytomegalovirus (CMV) enhancer/chicken beta-actin (CB) promoter. These vectors were functional in vitro, as judged by increased expression of mRNA in vector-transduced deficient cell lines and correction of the biochemical defect in PDH activity in these cells. Approximately 30% of wild-type levels of PDH activity were restored under conditions with which only about 15% of cells were transduced. These same vectors were then used in vivo to transduce neurons within the rat striatum. Gene transfer, expression, and translocation into mitochondria were observed, without any obvious untoward effects. In vivo vector-mediated PDH expression persisted for at least 1 year after injection, indicating the stability of gene transfer. These studies provide the basis for future efforts to develop a recombinant AAV (rAAV)-based gene therapy approach for the correction of PDC deficiency.

Analysis of exonic mutations leading to exon skipping in patients with pyruvate dehydrogenase E1 alpha deficiency.

The pyruvate dehydrogenase (PDH) complex is situated at a key position in energy metabolism and is responsible for the conversion of pyruvate to acetyl CoA. In the literature, two unrelated patients with a PDH complex deficiency and splicing out of exon 6 of the PDH E1 alpha gene have been described, although intronic/exonic boundaries on either side of exon 6 were completely normal. Analysis of exon 6 in genomic DNA of these patients revealed two exonic mutations, a silent and a missense mutation. Although not experimentally demonstrated, the authors in both publications suggested that the exonic mutations were responsible for the exon skipping. In this work, we were able to demonstrate, by performing splicing experiments, that the two exonic mutations described in the PDH E1 alpha gene lead to aberrant splicing. We observed a disruption of the predicted wild-type pre-mRNA secondary structure of exon 6 by the mutated sequences described. However, when we constructed mutations that either reverted or disrupted the wild-type predicted pre-mRNA secondary structure of exon 6, we were unable to establish a correlation between the aberrant splicing and disruption of the predicted structure. The mutagenic experiments described here and the silent mutation found in one of the patients suggest the presence of an exonic splicing enhancer in the middle region of exon 6 of the PDH E1alpha gene.

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.

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.

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.