We have studied the consequences of two homoplasmic, pathogenic point mutations (T7512C and G7497A) in the tRNA(Ser(UCN)) gene of mitochondrial (mt) DNA using osteosarcoma cybrids. We identified a severe reduction of tRNA(Ser(UCN)) to levels below 10% of controls for both mutations, resulting in a 40% reduction in mitochondrial protein synthesis rate and in a respiratory chain deficiency resemb...

We have studied the consequences of two homoplasmic, pathogenic point mutations (T7512C and G7497A) in the tRNA gene of mitochondrial (mt) DNA using osteosarcoma cybrids. We identified a severe reduction of tRNA to levels below 10% of controls for both mutations, resulting in a 40% reduction in mitochondrial protein synthesis rate and in a respiratory chain deficiency resembling that in the pat...

For any mitochondrial DNA (mtDNA) mutation, the ratio of mutant to wild-type mtDNA (% heteroplasmy) varies across tissues, with low levels in leukocytes and high levels in postmitotic tissues (e.g., skeletal muscle). Direct sequencing is the gold-standard method used to detect novel mutations, but can only reliably detect % heteroplasmy >25%, which is rare in leukocytes. Therefore, we investiga...

We characterized an unusual tRNA-like sequence that had been found inserted in suppressive variants of the mitochondrial retroplasmid of Neurospora intermedia strain Varkud. We previously identified two forms of the tRNA-like sequence, one of 64 nt (TRL-64) and the other of 78 nt (TRL-78) containing a 14-nt internal insertion in the anticodon stem at a position expected for a nuclear tRNA intro...

Mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episode (MELAS) and myoclonic epilepsy and ragged-red fibers (MERRF) are rare disorders caused by point mutation of the tRNA gene of the mitochondrial genome. To understand the pathogenetic mechanism of MELAS and MERRF, we studied four patients. Serially sectioned frozen muscle specimens with a battery of histochemical stai...

Mutations in the mitochondrial genome have been found to be associated with essential hypertension. Here, we report the clinical and molecular characterization of a three-generation Han Chinese family with maternally inherited hypertension. Most strikingly, this pedigree exhibited a high penetrance of hypertension. Sequence analysis of the mitochondrial genome showed the presence of a homoplasm...

The mammalian mitochondrial genome contains a single tRNA(Met) gene that gives rise to the initiator and elongator tRNA(Met). It is generally believed that mitochondrial protein synthesis begins with formylmethionyl-tRNA, which indicates that the formylation of mitochondrial Met-tRNA specifies its participation in initiation through its interaction with initiation factor 2 (IF-2). However, rece...

Confirming the pathogenicity of mitochondrial tRNA point mutations is one of the classical challenges in the field of mitochondrial medicine. In addition to genetic and functional studies, the evaluation of a genetic change using a pathogenicity scoring system is extremely useful to discriminate between disease-causing mutations from neutral polymorphisms. The pathogenicity scoring system is ve...

Described in 2005 by Bonnefond, L. et al, IARS2 (OMIM 612801) is a mitochondrial isoleucyl-tRNA synthetase encoded the nucleus. Phenotypically, mutation expressed broad clinical spectrum, which includes Leigh Syndrome (LS) as well extra-neurological effects. We described 7-year-old boy who presented global developmental delay, hypotonia and epilepsy, evolving with epileptic encephalopathy. An M...

The peptide nucleic acid (PNA)-directed PCR clamping technique was modified and applied to the detection of mitochondrial DNA mutations with low heteroplasmy. This method is extremely specific, eliminating false positives in the absence of mutant molecules, and highly sensitive, being capable of detecting mutations at the level of 0.1% of total molecules. Moreover, the reaction can be multiplex...