Human blood-derived lymphoblastoid cybrids for assessment of mitochondrial tRNAs deficiency by MTO1 silence

Abstract

Mutations in the mitochondrial translation optimization 1 (MTO1) gene can cause hypertrophic cardiomyopathy. Although the functional role of MTO1 deficiency in certain cells is gradually confirmed, the phenotype of MTO1 deficiency in a lymphoblastoid cybrid line is not yet reported. In this study, we characterized changes of mitochondrial function in MTO1 silenced cybrid cells derived from human lymphoblastoids, immature white blood cells that give rise to lymphocytes. We showed that MTO1 silence decreased the levels of 2-thiourylation of mitochondrial tRNALys, tRNAGlu, and tRNAGln, nevertheless, the aminoacylation efficiency of tRNALys and the steady state of mitochondrial tRNAs were elevated. These aberrant tRNA changes caused a significant decrease in protein levels of oxidative phosphorylation complex subunits including complex I, III, IV and V. Furthermore, dysfunctional mitochondria promoted apoptosis in stress, evidenced by elevated ratios of apoptotic cells and increased levels of apoptosis-activated proteins in the MTO1 knockdown cell lines, as compared to the controls. Our data provide new insights into the important functional role of MTO1 in lymphoblastoid mitochondria. We envision the cybrid cell line approach we have established provides an alternative model for the cardiac tissue of high-energy demands characteristics, and they hold promises for the diagnosis and drug screening for the therapeutic agents of hypertrophic cardiomyopathy caused by MTO1 dysfunction.