Biomedical subjects

Garry K Brown

Publications and source records attributed to Garry K Brown.

6 recordsLinked to original sources

PubMed2006

Mutations in the gene encoding 3-hydroxyisobutyryl-CoA hydrolase results in progressive infantile neurodegeneration.

Only a single patient with 3-hydroxyisobutyryl-CoA hydrolase deficiency has been described in the literature, and the molecular basis of this inborn error of valine catabolism has remained unknown until now. Here, we present a second patient with 3-hydroxyisobutyryl-CoA hydrolase deficiency, who was identified through blood spot acylcarnitine analysis showing persistently increased levels of hydroxy-C(4)-carnitine. Both patients manifested hypotonia, poor feeding, motor delay, and subsequent neurological regression in infancy. Additional features in the newly identified patient included episodes of ketoacidosis and Leigh-like changes in the basal ganglia on a magnetic resonance imaging scan. In cultured skin fibroblasts from both patients, the 3-hydroxyisobutyryl-CoA hydrolase activity was deficient, and virtually no 3-hydroxyisobutyryl-CoA hydrolase protein could be detected by western blotting. Molecular analysis in both patients uncovered mutations in the HIBCH gene, including one missense mutation in a conserved part of the protein and two mutations affecting splicing. A carefully interpreted acylcarnitine profile will allow more patients with 3-hydroxyisobutyryl-CoA hydrolase deficiency to be diagnosed.

Base Sequence↗

PubMed2005

Clinical and genetic spectrum of pyruvate dehydrogenase deficiency: dihydrolipoamide acetyltransferase (E2) deficiency.

Pyruvate dehydrogenase deficiency is a major cause of primary lactic acidosis and neurological dysfunction in infancy and early childhood. Most cases are caused by mutations in the X-linked gene for the E1alpha subunit of the complex. Mutations in DLAT, the gene encoding dihydrolipoamide acetyltransferase, the E2 core component of the complex, have not been described previously. We report two unrelated patients with pyruvate dehydrogenase deficiency caused by defects in the E2 subunit. Both patients are less severely affected than typical patients with E1alpha mutations and both have survived well into childhood. Episodic dystonia was the major neurological manifestation, with other more common features of pyruvate dehydrogenase deficiency, such as hypotonia and ataxia, being less prominent. The patients had neuroradiological evidence of discrete lesions restricted to the globus pallidus, and both are homozygous for different mutations in the DLAT gene. The clinical presentation and neuroradiological findings are not typical of pyruvate dehydrogenase deficiency and extend the clinical and mutational spectrum of this condition.

Autoantigens↗

PubMed2004

Mutations in the gene for the E1beta subunit: a novel cause of pyruvate dehydrogenase deficiency.

We describe two unrelated patients with pyruvate dehydrogenase (PDH) deficiency attributable to mutations in the gene encoding the E1beta subunit of the complex. This is a previously unrecognised form of PDH deficiency, which most commonly results from mutations in the X-linked gene for the E1alpha subunit. Both patients had reduced immunoreactive E1beta protein and both had missense mutations in the E1beta gene. Activity of the PDH complex was restored in cultured fibroblasts from both patients by transfection and expression of the normal E1beta coding sequence.

Humans↗

PubMed2002

Pyruvate dehydrogenase E3 binding protein deficiency.

Primary defects of the E3 binding protein component of the pyruvate dehydrogenase complex appear to be a rare cause of pyruvate dehydrogenase deficiency. We describe two new, unrelated patients with mutations in the E3 binding protein gene, in both cases involving the conserved dinucleotides of splice junctions. Both patients presented with delayed development and lactic acidosis, features that are also found in patients with the more common pyruvate dehydrogenase E1 alpha subunit deficiency; however, they both had significant residual enzyme activity in cultured fibroblasts and prolonged survival.

Adolescent↗

PubMed2002

Heterogeneous distribution of pyruvate dehydrogenase in the matrix of mitochondria.

A fusion protein between GFP and the E1alpha subunit of the pyruvate dehydrogenase (PDH) complex was created and shown to assemble into functional PDH complexes using immunoprecipitation and activity assays. The expression of this GFP-E1alpha chimera is specific to mitochondria and results in two different fluorescence patterns. These patterns have been distinguished by immunolabeling experiments using monoclonal antibodies against PDH subunits and GFP. The bright, localized fluorescent spots represent the assembled form of the GFP-E1alpha in PDH complexes. The uniform, dim fluorescence is given by the unassembled chimera free to diffuse throughout the mitochondrial reticulum. This study reveals a discrete, heterogeneous distribution of PDH complexes in the matrix of mitochondria, both in cells with normal and reduced levels of PDH. The uneven arrangement of PDH complexes is maintained over time and most likely reflects the structural and metabolic compartmentalization of mitochondria.

Journal Article↗

PubMed2002

Detection of pyruvate dehydrogenase E1 alpha-subunit deficiencies in females by immunohistochemical demonstration of mosaicism in cultured fibroblasts.

Deficiency of the E1 alpha-subunit of the pyruvate dehydrogenase (PDH) complex is an X-linked inborn error of metabolism and one of the major causes of lactic acidosis in children. Although most heterozygous females manifest symptoms of the disease, it is often difficult to establish the diagnosis as results based on measurement of total PDH activity, and E1 alpha-immunoreactive protein in patient fibroblasts may be ambiguous because of the variability in the pattern of X chromosome inactivation. We report the development of a set of monoclonal antibodies (MAbs) specific to four subunits of the PDH complex that can be used for detection of PDH E1 alpha deficiency. We also show that anti-E1 alpha and anti-E2 MAbs, when used in immunocytochemical analysis, can detect mosaicism in cell cultures from female patients in which as few as 2-5% of cells express the deficiency. This immunocytochemical approach, which is fast, reliable, and quantitative, will be particularly useful in identifying females with PDH E1 alpha-subunit deficiency as a precursor to mutation analysis.

Antibodies, Monoclonal↗