title: Mutations in human lipoyltransferase gene LIPT1 cause a Leigh disease with secondary deficiency for pyruvate and alpha-ketoglutarate dehydrogenase.
abstract: BACKGROUND
  Synthesis and apoenzyme attachment of lipoic acid have emerged as a new complex metabolic pathway. Mutations in several genes involved in the lipoic acid de novo pathway have recently been described (i.e., LIAS, NFU1, BOLA3, IBA57), but no mutation was found so far in genes involved in the specific process of attachment of lipoic acid to apoenzymes pyruvate dehydrogenase (PDHc), α-ketoglutarate dehydrogenase (α-KGDHc) and branched chain α-keto acid dehydrogenase (BCKDHc) complexes.
  
  
  METHODS
  Exome capture was performed in a boy who developed Leigh disease following a gastroenteritis and had combined PDH and α-KGDH deficiency with a unique amino acid profile that partly ressembled E3 subunit (dihydrolipoamide dehydrogenase / DLD) deficiency. Functional studies on patient fibroblasts were performed. Lipoic acid administration was tested on the LIPT1 ortholog lip3 deletion strain yeast and on patient fibroblasts.
  
  
  RESULTS
  Exome sequencing identified two heterozygous mutations (c.875C > G and c.535A > G) in the LIPT1 gene that encodes a mitochondrial lipoyltransferase which is thought to catalyze the attachment of lipoic acid on PDHc, α-KGDHc, and BCKDHc. Anti-lipoic acid antibodies revealed absent expression of PDH E2, BCKDH E2 and α-KGDH E2 subunits. Accordingly, the production of 14CO2 by patient fibroblasts after incubation with 14Cglucose, 14Cbutyrate or 14C3OHbutyrate was very low compared to controls. cDNA transfection experiments on patient fibroblasts rescued PDH and α-KGDH activities and normalized the levels of pyruvate and 3OHbutyrate in cell supernatants. The yeast lip3 deletion strain showed improved growth on ethanol medium after lipoic acid supplementation and incubation of the patient fibroblasts with lipoic acid decreased lactate level in cell supernatants.
  
  
  CONCLUSIONS
  We report here a putative case of impaired free or H protein-derived lipoic acid attachment due to LIPT1 mutations as a cause of PDH and α-KGDH deficiencies. Our study calls for renewed efforts to understand the mechanisms of pathology of lipoic acid-related defects and their heterogeneous biochemical expression, in order to devise efficient diagnostic procedures and possible therapies.
authors.forename: Yohan
authors.initials: Y
authors.lastname: Soreze
authors.forename: Audrey
authors.initials: A
authors.lastname: Boutron
authors.forename: Florence
authors.initials: F
authors.lastname: Habarou
authors.forename: Christine
authors.initials: C
authors.lastname: Barnerias
authors.forename: Luc
authors.initials: L
authors.lastname: Nonnenmacher
authors.forename: Hélène
authors.initials: H
authors.lastname: Delpech
authors.forename: Asmaa
authors.initials: A
authors.lastname: Mamoune
authors.forename: Dominique
authors.initials: D
authors.lastname: Chrétien
authors.forename: Laurence
authors.initials: L
authors.lastname: Hubert
authors.forename: Christine
authors.initials: C
authors.lastname: Bole-Feysot
authors.forename: Patrick
authors.initials: P
authors.lastname: Nitschke
authors.forename: Isabelle
authors.initials: I
authors.lastname: Correia
authors.forename: Claude
authors.initials: C
authors.lastname: Sardet
authors.forename: Nathalie
authors.initials: N
authors.lastname: Boddaert
authors.forename: Yamina
authors.initials: Y
authors.lastname: Hamel
authors.forename: Agnès
authors.initials: A
authors.lastname: Delahodde
authors.forename: Chris
authors.initials: C
authors.lastname: Ottolenghi
authors.affiliation: Reference Center of Inherited Metabolic Diseases, Imagine Institute, University Paris Descartes, Hospital Necker Enfants Malades, APHP, Paris, France. pascale.delonlay@nck.aphp.fr.
authors.forename: Pascale
authors.initials: P
authors.lastname: de Lonlay
mesh_terms: D000217:Acyltransferases / Q000235:genetics*; D000596:Amino Acids / Q000097:blood / Q000134:cerebrospinal fluid / Q000652:urine; D002352:Carrier Proteins / Q000235:genetics; D002478:Cells, Cultured; D005347:Fibroblasts / Q000378:metabolism; D006801:Humans; D015151:Immunoblotting; D007655:Ketoglutarate Dehydrogenase Complex / Q000172:deficiency / Q000235:genetics; D007658:Ketone Oxidoreductases / Q000172:deficiency / Q000235:genetics; D007888:Leigh Disease / Q000097:blood / Q000235:genetics* / Q000652:urine; D030481:Pyruvate Dehydrogenase (Lipoamide) / Q000235:genetics; D008063:Thioctic Acid / Q000097:blood / Q000134:cerebrospinal fluid / Q000652:urine
chemical_list: D000596:Amino Acids; D002352:Carrier Proteins; C426067:NFU1 protein, human; D008063:Thioctic Acid; D007658:Ketone Oxidoreductases; C053164:pyruvate dehydrogenase (NADP+); D030481:Pyruvate Dehydrogenase (Lipoamide); C065640:pyruvate dehydrogenase E1alpha subunit; D007655:Ketoglutarate Dehydrogenase Complex; D000217:Acyltransferases; C109735:lipoyltransferase I