title: Mutations in iron-sulfur cluster scaffold genes NFU1 and BOLA3 cause a fatal deficiency of multiple respiratory chain and 2-oxoacid dehydrogenase enzymes.
abstract: Severe combined deficiency of the 2-oxoacid dehydrogenases, associated with a defect in lipoate synthesis and accompanied by defects in complexes I, II, and III of the mitochondrial respiratory chain, is a rare autosomal recessive syndrome with no obvious causative gene defect. A candidate locus for this syndrome was mapped to chromosomal region 2p14 by microcell-mediated chromosome transfer in two unrelated families. Unexpectedly, analysis of genes in this area identified mutations in two different genes, both of which are involved in [Fe-S] cluster biogenesis. A homozygous missense mutation, c.545G>A, near the splice donor of exon 6 in NFU1 predicting a p.Arg182Gln substitution was found in one of the families. The mutation results in abnormal mRNA splicing of exon 6, and no mature protein could be detected in fibroblast mitochondria. A single base-pair duplication c.123dupA was identified in BOLA3 in the second family, causing a frame shift that produces a premature stop codon (p.Glu42Argfs(∗)13). Transduction of fibroblast lines with retroviral vectors expressing the mitochondrial, but not the cytosolic isoform of NFU1 and with isoform 1, but not isoform 2 of BOLA3 restored both respiratory chain function and oxoacid dehydrogenase complexes. NFU1 was previously proposed to be an alternative scaffold to ISCU for the biogenesis of [Fe-S] centers in mitochondria, and the function of BOLA3 was previously unknown. Our results demonstrate that both play essential roles in the production of [Fe-S] centers for the normal maturation of lipoate-containing 2-oxoacid dehydrogenases, and for the assembly of the respiratory chain complexes.
authors.affiliation: Genetics and Genome Biology, The Research Institute, The Hospital for Sick Children, Toronto, Canada.
authors.forename: Jessie M
authors.initials: JM
authors.lastname: Cameron
authors.forename: Alexandre
authors.initials: A
authors.lastname: Janer
authors.forename: Valeriy
authors.initials: V
authors.lastname: Levandovskiy
authors.forename: Nevena
authors.initials: N
authors.lastname: Mackay
authors.forename: Tracey A
authors.initials: TA
authors.lastname: Rouault
authors.forename: Wing-Hang
authors.initials: WH
authors.lastname: Tong
authors.forename: Isla
authors.initials: I
authors.lastname: Ogilvie
authors.forename: Eric A
authors.initials: EA
authors.lastname: Shoubridge
authors.forename: Brian H
authors.initials: BH
authors.lastname: Robinson
mesh_terms: D002352:Carrier Proteins / Q000235:genetics*; D003600:Cytosol / Q000378:metabolism; D004579:Electron Transport; D005091:Exons; D005192:Family Health; D005260:Female; D005347:Fibroblasts / Q000378:metabolism; D006720:Homozygote; D006801:Humans; D007506:Iron-Sulfur Proteins / Q000378:metabolism; D008297:Male; D008928:Mitochondria / Q000378:metabolism; D024101:Mitochondrial Proteins; D009154:Mutation; D020125:Mutation, Missense; D010088:Oxidoreductases / Q000378:metabolism*; D011506:Proteins / Q000235:genetics*
chemical_list: C533597:BolA3 protein, human; D002352:Carrier Proteins; D007506:Iron-Sulfur Proteins; D024101:Mitochondrial Proteins; C426067:NFU1 protein, human; D011506:Proteins; D010088:Oxidoreductases