Mutation at position 5628 in the mitochondrial tRNAAla gene in a Chinese pedigree with maternally diabetes mellitus

Background: To investigate the clinical, genetic and molecular characteristics of mitochondrial diabetes mellitus (MDM). Methods: Resultant variants were evaluated for evolutionary conservation, allelic frequencies, and structural and functional consequences. The mitochondrial function including mitochondrial tRNAAla levels, protein synthesis, membrane potential, adenosine triphosphate (ATP) production, and reactive oxygen species (ROS) generation were measured using lymphoblastoid cell lines carrying the m.5628T>C mutation and 2 controls .Results: We observed differences in the severity and age of onset in diabetes in affected maternally-related individuals, and through amolecular of the complete mitochondrial genome in this family, we identified a homoplasmic m.5628T>C mutation, located at conventional position 31 of tRNAAla, and we further detected distinct sets of mtDNA polymorphisms belonging to haplogroup L1. The identified mutation was further found be important for tRNA identity and stability. Using cellular models, we were able to determine that the respiratory deficiency caused arising as a consequence of the m.5628T>C mutation led to decreased efficiency of mitochondrial tRNAAla levels, protein synthesis, mitochondrial ATP synthesis and a reduced mitochondrial membrane potential.These mitochondrial dysfunctions caused an increase in the production of reactive oxygen species in the mutant cell lines. Conclusions: These data provide a direct evidence that novel m.5628T>C mutation may be associated with MDM, thus, offering novel insights into the understanding of pathophysiology of MDM.