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Tyynismaa H.,Research Programs Unit | Tyynismaa H.,University of Helsinki | Schon E.A.,Columbia University
EMBO Molecular Medicine | Year: 2014

Mutations in mitochondrial DNA are an important cause of human disease and from a therapeutic standpoint, these disorders are currently untreatable. New studies now show that a non-cognate mitochondrial aminoacyl tRNA synthetase can overcome the respiratory defect caused by an mt-tRNA mutation and that the isolated carboxy-terminal domain of human mt-leucyl tRNA synthetase can ameliorate the pathologic phenotype. © 2014 The Authors.. Source

Suomalainen A.,Research Programs Unit | Suomalainen A.,University of Helsinki
EMBO Molecular Medicine | Year: 2015

This commentary inaugurates a new review series in EMBO Molecular Medicine focused on mitochondrial diseases. This area of medicine, which actually encompasses most disease areas, has long since come of age and is now positioned for the next leap toward the development of effective therapies. The aims of the review series are to offer a comprehensive overview of this exciting area of medicine and research and to provide timely discussions for clinicians and investigators on the new discoveries elucidating how mitochondrial metabolism contributes to an expanding group of complex, heterogeneous, and difficult-to-tackle diseases. © 2015 EMBO. Source

Wilbe M.,Swedish University of Agricultural Sciences | Wilbe M.,Uppsala University | Kozyrev S.V.,Uppsala University | Farias F.H.G.,Uppsala University | And 11 more authors.
PLoS Genetics | Year: 2015

The complexity of clinical manifestations commonly observed in autoimmune disorders poses a major challenge to genetic studies of such diseases. Systemic lupus erythematosus (SLE) affects humans as well as other mammals, and is characterized by the presence of antinuclear antibodies (ANA) in patients’ sera and multiple disparate clinical features. Here we present evidence that particular sub-phenotypes of canine SLE-related disease, based on homogenous (ANAH) and speckled ANA (ANAS) staining pattern, and also steroid-responsive meningitis-arteritis (SRMA) are associated with different but overlapping sets of genes. In addition to association to certain MHC alleles and haplotypes, we identified 11 genes (WFDC3, HOMER2, VRK1, PTPN3, WHAMM, BANK1, AP3B2, DAPP1, LAMTOR3, DDIT4L and PPP3CA) located on five chromosomes that contain multiple risk haplotypes correlated with gene expression and disease sub-phenotypes in an intricate manner. Intriguingly, the association of BANK1 with both human and canine SLE appears to lead to similar changes in gene expression levels in both species. Our results suggest that molecular definition may help unravel the mechanisms of different clinical features common between and specific to various autoimmune disease phenotypes in dogs and humans. © 2015 Wilbe et al. Source

Conde C.D.,Austrian Academy of Sciences | Zhang S.-Y.,Rockefeller University | Zhang S.-Y.,French Institute of Health and Medical Research | Zhang S.-Y.,University of Paris Descartes | And 56 more authors.
New England Journal of Medicine | Year: 2015

BACKGROUND Combined immunodeficiencies are marked by inborn errors of T-cell immunity in which the T cells that are present are quantitatively or functionally deficient. Impaired humoral immunity is also common. Patients have severe infections, autoimmunity, or both. The specific molecular, cellular, and clinical features of many types of combined immunodeficiencies remain unknown. METHODS We performed genetic and cellular immunologic studies involving five unrelated children with early-onset invasive bacterial and viral infections, lymphopenia, and defective T-cell, B-cell, and natural killer (NK)-cell responses. Two patients died early in childhood; after allogeneic hematopoietic stem-cell transplantation, the other three had normalization of T-cell function and clinical improvement. RESULTS We identified biallelic mutations in the dedicator of cytokinesis 2 gene (DOCK2) in these five patients. RAC1 activation was impaired in the T cells. Chemokine-induced migration and actin polymerization were defective in the T cells, B cells, and NK cells. NK-cell degranulation was also affected. Interferon-α and interferon-λ production by peripheral-blood mononuclear cells was diminished after viral infection. Moreover, in DOCK2-deficient fibroblasts, viral replication was increased and virus-induced cell death was enhanced; these conditions were normalized by treatment with interferon alfa-2b or after expression of wild-type DOCK2. CONCLUSIONS Autosomal recessive DOCK2 deficiency is a new mendelian disorder with pleiotropic defects of hematopoietic and nonhematopoietic immunity. Children with clinical features of combined immunodeficiencies, especially with early-onset, invasive infections, may have this condition. Copyright © 2015 Massachusetts Medical Society. Source

Elo J.M.,Research Programs Unit | Yadavalli S.S.,Ohio State University | Euro L.,Research Programs Unit | Isohanni P.,Research Programs Unit | And 15 more authors.
Human Molecular Genetics | Year: 2012

Next-generation sequencing has turned out to be a powerful tool to uncover genetic basis of childhood mitochondrial disorders. We utilized whole-exome analysis and discovered novel compound heterozygous mutations in FARS2 (mitochondrial phenylalanyl transfer RNA synthetase), encoding the mitochondrial phenylalanyl transfer RNA (tRNA) synthetase (mtPheRS) in two patients with fatal epileptic mitochondrial encephalopathy. The mutations affected highly conserved amino acids, p.I329T and p.D391V. Recently, a homozygous FARS2 variant p.Y144C was reported in a Saudi girl with mitochondrial encephalopathy, but the pathogenic role of the variant remained open. Clinical features, including postnatal onset, catastrophic epilepsy, lactic acidemia, early lethality and neuroimaging findings of the patients with FARS2 variants, resembled each other closely, and neuropathology was consistent with Alpers syndrome. Our structural analysis of mtPheRS predicted that p.I329T weakened ATP binding in the aminoacylation domain, and in vitro studies with recombinant mutant protein showed decreased affinity of this variant to ATP. Furthermore, p.D391V and p.Y144C were predicted to disrupt synthetase function by interrupting the rotation of the tRNA anticodon stem-binding domain from a closed to an open form. In vitro characterization indicated reduced affinity of p.D391V mutant protein to phenylalanine, whereas p.Y144C disrupted tRNA binding. The stability of p.I329T and p.D391V mutants in a refolding assay was impaired. Our results imply that the three FARS2 mutations directly impair aminoacylation function and stability of mtPheRS, leading to a decrease in overall tRNA charging capacity. This study establishes a new genetic cause of infantile mitochondrial Alpers encephalopathy and reports a new mitochondrial aminoacyl-tRNA synthetase as a cause of mitochondrial disease. © The Author 2012. Published by Oxford University Press. All rights reserved. Source

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