Heteroplasmy levels of mitochondrial tRNALeu(UUR) A3243G mutation and clinical features in a Chinese family with mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes syndrome

Abstract

Objective To investigate the clinical manifestation, biochemically detected data, and radiographic features of a pedigree with suspected mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS) syndrome, and to explore the correlations between the clinical features and the mutant heteroplasmy levels of mitochondrial genome. Methods The personal details, histories of stroke-like episodes and seizures within the proband and 11 members in the maternal lineage of the family were collected. Routine blood examinations and plasma lactate levels before and after movements of these family members were detected, followed by cephalic MRI examinations. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and DNA sequencing were used to detect and validate the A3243G point mutation in mitochondrial genome, and real-time PCR were used to quantify the mutation proportion of A3243G. Results Typical symptoms of MELAS such as seizures, stroke-like episodes and hyperlactacidemia and atypical symptoms such as growth failure, exercise intolerance, fevers and migraines were observed on several members in the pedigree. Cephalic MRI findings performed during episode periods were in accord with the typical radiographic features of MELAS and cerebellar atrophy was commonly observed. Family members on the maternal side all harbored the point mutation on 3243 site in mitochondrial genome. Meanwhile, patients with higher heteroplasmy levels relatively manifested more typically and severely according to the clinical observation. Conclusions The pedigree is diagnosed with maternal inheritance of MELAS syndrome. The main cause can be attributed to a mitochonorial A3243G mutation.The mutant heteroplasmy levels of hemocytes in peripheral blood are positively associated with genetic relationship, seizure anticipation, plasma lactate data and other clinical features. Key words: MELAS syndrome; Genome, mitochondrial; Point mutation; Pedigree