[Correlation of mitochondrial tRNA variants with coronary heart disease in a Chinese pedigree]

To explore the correlation of mitochondrial DNA (mtDNA) variants and coronary heart disease (CHD) in a Chinese pedigree and the possible molecular mechanisms.

A Chinese pedigree featuring matrilineal inheritance of CHD who visited Hangzhou First People's Hospital in May 2022 was selected as the study subject. Clinical data of the proband and her affected relatives was collected. By sequencing the mtDNA of the proband and her pedigree members, candidate variants were identified through comparison with wild type mitochondrial genes. Conservative analysis among various species was conducted, and bioinformatics software was used to predict the impact of variants on the secondary structure of tRNA. Real-time PCR was carried out to determine the copy number of mtDNA, and a transmitochondrial cell line was established for analyzing the mitochondrial functions, including membrane potential and ATP level.

This pedigree had contained thirty-two members from four generations. Among ten maternal members, four had CHD, which yielded a penetrance rate of 40%. Sequence analysis of proband and her matrilineal relatives revealed the presence of a novel m.4420A>T variant and a m.10463T>C variant, both of which were highly conserved among various species. Structurally, the m.4420A>T variant had occurred at position 22 in the D-arm of tRNAMet, which disrupted the 13T-22A base-pairing, while the m.10463T>C variant was located at position 67 in the acceptor arm of tRNAArg, a position critical for steady-state level of the tRNA. Functional analysis revealed that patients with the m.4420A>T and m.10463T>C variants exhibited much fewer copy number of mtDNA and lower mitochondrial membrane potential (MMP) and ATP contents (P < 0.05), which were decreased by approximately 50.47%, 39.6% and 47.4%, respectively.

Mitochondrial tRNAMet 4420A>T and tRNAArg 10463T>C variants may underlay the maternally transmitted CHD in this pedigree, which had shown variation in mtDNA homogeneity, age of onset, clinical phenotype and other differences, suggesting that nuclear genes, environmental factors and mitochondrial genetic background have certain influence on the pathogenesis of CHD.