Mutation of the mitochondrial tyrosyl-tRNA synthetase gene, YARS2, causes myopathy, lactic acidosis, and sideroblastic anemia--MLASA syndrome.
Mitochondrial respiratory chain disorders are a heterogeneous group of disorders in which the underlying genetic defect is often unknown. We have identified a pathogenic mutation (c.156C>G [p.F52L]) in YARS2, located at chromosome 12p11.21, by using genome-wide SNP-based homozygosity analysis of a family with affected members displaying myopathy, lactic acidosis, and sideroblastic anemia (MLASA). We subsequently identified the same mutation in another unrelated MLASA patient. The YARS2 gene product, mitochondrial tyrosyl-tRNA synthetase (YARS2), was present at lower levels in skeletal muscle whereas fibroblasts were relatively normal. Complex I, III, and IV were dysfunctional as indicated by enzyme analysis, immunoblotting, and immunohistochemistry. A mitochondrial protein-synthesis assay showed reduced levels of respiratory chain subunits in myotubes generated from patient cell lines. A tRNA aminoacylation assay revealed that mutant YARS2 was still active; however, enzyme kinetics were abnormal compared to the wild-type protein. We propose that the reduced aminoacylation activity of mutant YARS2 enzyme leads to decreased mitochondrial protein synthesis, resulting in mitochondrial respiratory chain dysfunction. MLASA has previously been associated with PUS1 mutations; hence, the YARS2 mutation reported here is an alternative cause of MLASA.
Riley
Lisa G
LG
Genetic Metabolic Disorders Research Unit, Children's Hospital at Westmead, Sydney 2145, Australia.
Cooper
Sandra
S
Hickey
Peter
P
Rudinger-Thirion
Joëlle
J
McKenzie
Matthew
M
Compton
Alison
A
Lim
Sze Chern
SC
Thorburn
David
D
Ryan
Michael T
MT
Giegé
Richard
R
Bahlo
Melanie
M
Christodoulou
John
J
D000140:Acidosis, Lactic / Q000235:genetics*; D000293:Adolescent; D000328:Adult; D000595:Amino Acid Sequence; D000756:Anemia, Sideroblastic / Q000235:genetics*; D002648:Child; D002675:Child, Preschool; D002881:Chromosomes, Human, Pair 12 / Q000235:genetics; D003241:Consanguinity; D042967:Electron Transport Complex I / Q000502:physiology; D014450:Electron Transport Complex III / Q000502:physiology; D003576:Electron Transport Complex IV / Q000502:physiology; D005260:Female; D056726:Genetic Association Studies; D008040:Genetic Linkage; D055106:Genome-Wide Association Study; D005838:Genotype; D006801:Humans; D007223:Infant; D008297:Male; D008928:Mitochondria / Q000201:enzymology*; D008969:Molecular Sequence Data; D009135:Muscular Diseases / Q000235:genetics*; D009154:Mutation; D010375:Pedigree; D013577:Syndrome; D014448:Tyrosine-tRNA Ligase / Q000235:genetics*; D055815:Young Adult
D003576:Electron Transport Complex IV; D014448:Tyrosine-tRNA Ligase; D042967:Electron Transport Complex I; D014450:Electron Transport Complex III