Mitochondrial tRNA(Cys) mutation A5823G in a patient with motor neuron disease and temporal lobe epilepsy.

We discovered a new homoplasmic mutation in the mitochondrial cysteine tRNA of a 60-year-old Caucasian male suffering from asymmetrical pure lower motor neuron disease (MND) and temporal lobe epilepsy (TLE). Furthermore, titrations with Amytal, an inhibitor of NADH:CoQ oxidoreductase, revealed mild mitochondrial dysfunction in skeletal muscle tissue, which was described in patients with MND in an earlier report. The mutation was undetectable in 155 Caucasian controls of both sexes, in 40 MND patients and in 13 individuals suffering from TLE. It was, however, detected in a heteroplasmic state in the patient's mother, who did not suffer from a neurological disorder. Since this rare mutation affected a nonconserved base position and was not observed in MND or TLE materials, its relation to disease remains unclear.