Confirmation That MAT1A p.Ala259Val Mutation Causes Autosomal Dominant Hypermethioninemia

Methionine adenosyltransferase (MAT) I/III deficiency is an inborn error of metabolism caused by mutations in MAT1A, encoding the catalytic subunit of MAT responsible for the synthesis of S-adenosylmethionine, and is characterized by persistent hypermethioninemia. While historically considered a recessive disorder, a milder autosomal dominant form of MAT I/III deficiency occurs, though only the most common mutation p.Arg264His has ample evidence to prove dominant inheritance. We report a case of hypermethioninemia caused by the p.Ala259Val substitution and provide evidence of autosomal dominant inheritance by showing both maternal inheritance of the mutation and concomitant hypermethioninemia. The p.Ala259Val mutation falls in the dimer interface, and thus likely leads to dominant inheritance by a similar mechanism to that described in the previously reported dominant negative mutation, that is, by means of interference with subunits encoded by the wild-type allele

High Proportion of 22q13 Deletions and SHANK3 Mutations in Chinese Patients with Intellectual Disability

Intellectual disability (ID) is a heterogeneous disorder caused by chromosomal abnormalities, monogenic factors and environmental factors. 22q13 deletion syndrome is a genetic disorder characterized by severe ID. Although the frequency of 22q13 deletions in ID is unclear, it is believed to be largely underestimated. To address this issue, we used Affymetrix Human SNP 6.0 array to detect the 22q13 deletions in 234 Chinese unexplained ID patients and 103 controls. After the Quality Control (QC) test of raw data, 22q13 deletions were found in four out of 230 cases (1.7%), while absent in parents of the cases and 101 controls. A review of genome-wide microarray studies in ID was performed and the frequency of 22q13 deletions from the literatures was 0.24%, much lower than our report. The overlapping region shared by all 4 cases encompasses the gene SHANK3. A heterozygous de novo nonsense mutation Y1015X of SHANK3 was identified in one ID patient. Cortical neurons were prepared from embryonic mice and were transfected with a control plasmid, shank3 wild-type (WT) or mutant plasmids. Overexpression of the Y1015 mutant in neurons significantly affected neurite outgrowth compared with shank3 WT. These findings suggest that 22q13 deletions may be a more frequent cause for Chinese ID patients than previously thought, and the SHANK3 gene is involved in the neurite development

Data from: Degree of glutathione deficiency and redox imbalance depend on subtype of mitochondrial disease and clinical status

Mitochondrial disorders are associated with decreased energy production and redox imbalance. Glutathione plays a central role in redox signaling and protecting cells from oxidative damage. In order to understand the consequences of mitochondrial dysfunction on in vivo redox status, and to determine how this varies by mitochondrial disease subtype and clinical severity, we used a sensitive tandem mass spectrometry assay to precisely quantify whole blood reduced (GSH) and oxidized (GSSG) glutathione levels in a large cohort of mitochondrial disorder patients. Glutathione redox potential was calculated using the Nernst equation. Compared to healthy controls (n = 59), mitochondrial disease patients (n = 58) as a group showed significant redox imbalance (redox potential −251 mV±9.7, p<0.0001) with an increased level of oxidation by ~9 mV compared to controls (−260 mV±6.4). Underlying this abnormality were significantly lower whole blood GSH levels (p = 0.0008) and GSH/GSSG ratio (p = 0.0002), and significantly higher GSSG levels (p<0.0001) in mitochondrial disease patients compared to controls. Redox potential was significantly more oxidized in all mitochondrial disease subgroups including Leigh syndrome (n = 15), electron transport chain abnormalities (n = 10), mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (n = 8), mtDNA deletion syndrome (n = 7), mtDNA depletion syndrome (n = 7), and miscellaneous other mitochondrial disorders (n = 11). Patients hospitalized in metabolic crisis (n = 7) showed the greatest degree of redox imbalance at −242 mV±7. Peripheral whole blood GSH and GSSG levels are promising biomarkers of mitochondrial dysfunction, and may give insights into the contribution of oxidative stress to the pathophysiology of the various mitochondrial disorders. In particular, evaluation of redox potential may be useful in monitoring of clinical status or response to redox-modulating therapies in clinical trials

Clinical utility gene card for: Deletion 22q13 syndrome

International audienceNo abstract availabl

Degree of Glutathione Deficiency and Redox Imbalance Depend on Subtype of Mitochondrial Disease and Clinical Status

<div><p>Mitochondrial disorders are associated with decreased energy production and redox imbalance. Glutathione plays a central role in redox signaling and protecting cells from oxidative damage. In order to understand the consequences of mitochondrial dysfunction on <i>in vivo</i> redox status, and to determine how this varies by mitochondrial disease subtype and clinical severity, we used a sensitive tandem mass spectrometry assay to precisely quantify whole blood reduced (GSH) and oxidized (GSSG) glutathione levels in a large cohort of mitochondrial disorder patients. Glutathione redox potential was calculated using the Nernst equation. Compared to healthy controls (n = 59), mitochondrial disease patients (n = 58) as a group showed significant redox imbalance (redox potential −251 mV±9.7, p<0.0001) with an increased level of oxidation by ∼9 mV compared to controls (−260 mV±6.4). Underlying this abnormality were significantly lower whole blood GSH levels (p = 0.0008) and GSH/GSSG ratio (p = 0.0002), and significantly higher GSSG levels (p<0.0001) in mitochondrial disease patients compared to controls. Redox potential was significantly more oxidized in all mitochondrial disease subgroups including Leigh syndrome (n = 15), electron transport chain abnormalities (n = 10), mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (n = 8), mtDNA deletion syndrome (n = 7), mtDNA depletion syndrome (n = 7), and miscellaneous other mitochondrial disorders (n = 11). Patients hospitalized in metabolic crisis (n = 7) showed the greatest degree of redox imbalance at −242 mV±7. Peripheral whole blood GSH and GSSG levels are promising biomarkers of mitochondrial dysfunction, and may give insights into the contribution of oxidative stress to the pathophysiology of the various mitochondrial disorders. In particular, evaluation of redox potential may be useful in monitoring of clinical status or response to redox-modulating therapies in clinical trials.</p></div

GSH_project_MasterList

Excel file containing oxidized and reduced glutathione data in patients and controls

Comparison of Glutathione Redox Status by Mitochondrial Disease Category.

<p>Glutathione indices for all mitochondrial disease patients combined, as well as for different subgroups of mitochondrial disease, are shown. The combined category excludes samples collected during times of metabolic crisis.</p><p>*comparing mitochondrial disease category to control, except for Metabolic Crisis category in which comparisons were made to mitochondrial disease patients not in crisis;</p><p>**significant at P<0.05.</p

Glutathione redox potential distribution curves.

<p>The redox potential distribution curve for each mitochondrial disease subgroup is compared to the normal distribution of control redox potential in order to show how distribution of redox potential differs from the controls. a) Mitochondrial disease patients combined, excluding those in metabolic crisis; b) Leigh syndrome patients; c) Electron transport chain disorder patients; d) Mitochondrial encephalomyopathy, lactic acidosis and stroke-like episode patients; e) mtDNA deletion patients; f) mtDNA depletion patients; g) Miscellaneous mitochondrial disease patients; g) Mitochondrial disease patients hospitalized in metabolic crisis. Normal distribution plots were created with SAS 9.4. The density of the normal distribution is the height for a given value on the x-axis.</p