To achieve this, we have performed WES of 11 MELAS patients and identified pathogenic mutation in nuclear encoded genes associated with mitochondrial encephalopathy (POLG, DGUOK, SUCLG2, TRNT1), sensorineural hearing loss, seizures, epileptic encephalopathy, and cardiomyopathy (LOXHD1, KCNQ1, KCNQ2 and MYH7). Here, POLG is linked to Mitochondrial encephalopathy.