Restoration of the mitochondrial citrate transporter by overexpression of SLC25A1 in primary deficient fibroblasts of patients with combined D-2- and L-2-hydroxyglutaric aciduria. G. S. Salomons1, E. A. Struys1, A. Pop1, E. E. Jansen1, M. R. Fernandez Ojeda1, W. A. Kanhai1, M. Kranendijk1, S. J. M. van Dooren1, M. R. Bevova2, E. A. Sistermans2, A. W. M. Nieuwint2, M. Barth3, T. Ben-Omran4, G. F. Hoffmann5, P. de Lonlay6, M. T. McDonald7, A. Meberg8, A. C. Mühlhausen9, C. Muntau10, J.-M. Nuoffer11, R. Parini12, M.-H. Read13, A. Renneberg14, R. Santer9, T. Strahleck16, E. van Schaftingen15, M. S. van der Knaap17, C. Jakobs1, B. Nota1 1) Metabolic Unit, VU University Med Center, Amsterdam, Netherlands; 2) Dept of Clin Genetics, VUmc, Amsterdam, Netherlands; 3) Génétique CHU Angers, Angers, France; 4) Clinical and Metabolic Genetics,HMC WCMC, Doha, Qatar; 5) Dept Kinderheilkunde I, Heidelberg, Germany; 6) Inh Metabolic Diseases, Hôpital Necker, Paris, France; 7) Div of Med Genetics, Duke University, Durham, United States; 8) Neonatal Unit, Vestfold Hospital Trust, Txnsberg, Norway; 9) Ped Metabolic Med, Univ Childs Hospital, Hamburg, Germany; 10) Dept of Mol Paediatrics,Ludwig-Max. Univ, Munich, Germany; 11) Div of Ped Endocrinology, Univ. of Bern, Bern, Switzerland; 12) Dept of Pediatrics, Fondazione "MBBM", Monza, Italy; 13) Laboratoire de biochimie, CHU de Caen, Caen, France; 14) Dept of Neuropediatrics, Klin Bürgerpark, Bremerhaven, Germany; 15) Lab of Physiol Chem, de Duve Institute, Brussels, Belgium; 16) Dept of Neonatology, Olgahospital, Stuttgart, Germany; 17) Dept of Child Neurology, VUmc, Amsterdam, Netherlands.

   The Krebs cycle has a fundamental role in the ATP production in prokaryotic and eukaryotic cells. Both enantiomers of 2-hydroxyglutarate are directly linked to this fundamental energy production pathway and both are found to be elevated in certain neoplastic malignancies. D-2- and L-2-hydroxyglutaric acidurias are rare neurometabolic disorders. We showed that one variant of 2-hydroxyglutaric aciduria - D-2-hydroxyglutarate type I - (Kranenedijk et al, Science 2010) is caused by cancer-associated IDH2 germline mutations. Complementary to this finding, we recently reported pathogenic mutations in the mitochondrial citrate transporter gene (SLC25A1) using exome sequencing in 12 individuals with the combined D-2- and L-2-hydroxyglutaric aciduria (Nota et al, april 2013, Am J Hum Genet). We demonstrated impairment of mitochondrial citrate efflux by stable isotope labeled experiments in cultured skin fibroblasts. The absence of SLC25A1 protein in fibroblasts harboring null alleles (SLC25A1-/-) was shown by western blotting and could be restored by transfection of wild type SLC25A1. Overexpression of SLC25A1 also restored citrate efflux and decreased intracellular D-2- and L-2 hydroxyglutarate levels. These results prove that the mitochondrial citrate transporter is the cause of combined D-2- and L-2 hydroxyglutaric aciduria.

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