Mutations in Iron-Sulfur Cluster Scaffold Genes NFU1 and BOLA3 Cause a Fatal Deficiency of Multiple Respiratory Chain and 2-Oxoacid Dehydrogenase Enzymes

• Published in: American journal of human genetics 2011-10, Vol.89 (4), p.486-495
• Main Authors: Cameron, Jessie M., Janer, Alexandre, Levandovskiy, Valeriy, MacKay, Nevena, Rouault, Tracey A., Tong, Wing-Hang, Ogilvie, Isla, Shoubridge, Eric A., Robinson, Brian H.
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; Biosynthesis; Carrier Proteins - genetics; Chemical compounds; Cytosol - metabolism; Electron Transport; Enzymes; Exons; Family Health; Female; Fibroblasts - metabolism; Fundamental and applied biological sciences. Psychology; General aspects. Genetic counseling; Genetics of eukaryotes. Biological and molecular evolution; Homozygote; Humans; Iron-Sulfur Proteins - metabolism; Male; Medical genetics; Medical sciences; Mitochondria - metabolism; Molecular and cellular biology; Mutation; Mutation, Missense; Oxidoreductases - metabolism; Proteins - genetics; Signal transduction
• ISSN: 0002-9297; 1537-6605
• DOI: 10.1016/j.ajhg.2011.08.011

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.