Simple detection of tRNA(Lys) mutation in myoclonus epilepsy associated with ragged-red fibers (MERRF) by polymerase chain reaction with a mismatched primer.

We developed a simple method for the detection of a tRNA(Lys) mutation in myoclonus epilepsy associated with ragged-red fibers (MERRF) by polymerase chain reaction with use of a mismatched primer. Although the tRNA(Lys) mutation does not alter recognition sequences for commercially available restriction enzymes, we have successfully changed two nucleotides flanking the A to G mutation at nucleotide position 8344 in a tRNA(Lys) gene of a mitochondrial genome. As a result, the mutation can be detected as a Nae I restriction fragment length polymorphism. With this method, all eight MERRF patients and an asymptomatic mother of a MERRF patient, from six independent families, had the same tRNA(Lys) mutation. Our method is simple and should also be useful for the quantitation of heteroplasmies.