Inhibition of mitochondrial translation in fibroblasts from a patient expressing the KARS p.(Pro228Leu) variant and presenting with sensorineural deafness, developmental delay, and lactic acidosis. Issue 12 (3rd October 2018)

• Record Type: Journal Article
• Authors: Ruzzenente, Benedetta; Assouline, Zahra; Barcia, Giulia; Rio, Marlène; Boddaert, Nathalie; Munnich, Arnold; Rötig, Agnès; Metodiev, Metodi D.
• Is Part Of: Human mutation. Volume 39:Issue 12(2018)
• Page Start: 2047
• Page End: 2059
• Publication Date: 2018-10-03
• Subjects: cytosolic translation -- KARS -- lysyl‐tRNA synthetase -- mitochondrial disease -- mitochondrial translation -- OXPHOS deficiency; Human chromosome abnormalities -- Periodicals; Mutation (Biology) -- Periodicals; 616.04205
• DOI: 10.1002/humu.23657
• Languages: English
• ISSNs: 1059-7794

Abstract

Abstract: Aminoacyl‐tRNA synthetases are ubiquitous enzymes, which universally charge tRNAs with their cognate amino acids for use in cytosolic or organellar translation. In humans, mutations in mitochondrial tRNA synthetases have been linked to different tissue‐specific pathologies. Mutations in the KARS gene, which encodes both the cytosolic and mitochondrial isoform of lysyl‐tRNA synthetase, cause predominantly neurological diseases that often involve deafness, but have also been linked to cardiomyopathy, developmental delay, and lactic acidosis. Using whole exome sequencing, we identified two compound heterozygous mutations, NM_001130089.1:c.683C>T p.(Pro228Leu) and NM_001130089.1:c.1438del p.(Leu480TrpfsX3), in a patient presenting with sensorineural deafness, developmental delay, hypotonia, and lactic acidosis. Nonsense‐mediated mRNA decay eliminated the truncated mRNA transcript, rendering the patient hemizygous for the missense mutation. The c.683C>T mutation was previously described, but its pathogenicity remained unexamined. Molecular characterization of patient fibroblasts revealed a multiple oxidative phosphorylation deficiency due to impaired mitochondrial translation, but no evidence of inhibition of cytosolic translation. Reintroduction of wild‐type mitochondrial KARS, but not the cytosolic isoform, rescued this phenotype confirming the disease‐causing nature of p.(Pro228Leu) exchange and demonstrating the mitochondrial etiology of the disease. We propose that mitochondrial translation deficiency is the probable disease culprit in this and possibly other patients with mutations in KARS . Abstract : KARS encodes the nearly identical cytosolic and mitochondrial isoforms of the lysyl‐tRNA synthetase, which aminoacylate tRNA Lys used in cytosolic and mitochondrial translation. Despite affecting an identical amino acid in both KARS isoforms, the disease‐causing variant p.(Pro228Leu) inhibits specifically mitochondrial, but not cytosolic, translation.