Detection of a new case harboring mitochondrial A3243G mutation of MELAS syndrome

Mitochondrial genome A3243G mutation in the tRNALeu(UUR)  encodinggene (MTTL)is the main cause of mitochondrial encephalopathy, lactic acidosis and stroke-like episodes (MELAS). This mutation exists in heteroplasmic form and severity of the disease is affected by many factors including heteroplasmy level. In this study, a pediatric proband (female, 8 years old) was found to carry A3243G mutation at 77.6% of heteroplasmy by using PCR-RFLP in combination with real-time PCR. The results of  the A3243G mutation analysis of the proband’s family showed that her mother without any symptoms of encephalopathyalso carried the mutation at 7.9% of heteroplasmy whereas the mutation was not found in the proband’s healthy father and healthy sister, indicating that the proband received the A3243G mutation from her mother and the expression of MELAS syndromes depended on the level of heteroplasmy.