Heteroplasmic Variants of Mitochondrial DNA in Atherosclerotic Lesions of Human Aortic Intima.

Sobenin Sobenin,Grechko Grechko,Sukhorukov Sukhorukov,Medvedeva Medvedeva,Orekhov Orekhov,Smirnova Smirnova,Makeev Makeev,Sagaidak Sagaidak,Zhelankin Zhelankin,Khasanova Khasanova,Kolmychkova Kolmychkova,Sinyov Sinyov,Postnov Postnov

doi:10.3390/biom9090455

Abstract

Mitochondrial dysfunction and oxidative stress are likely involved in atherogenesis. Since the mitochondrial genome variation can alter functional activity of cells, it is necessary to assess the presence in atherosclerotic lesions of mitochondrial DNA (mtDNA) heteroplasmic mutations known to be associated with different pathological processes and ageing. In this study, mtDNA heteroplasmy and copy number (mtCN) were evaluated in the autopsy-derived samples of aortic intima differing by the type of atherosclerotic lesions. To detect mtDNA heteroplasmic variants, next generation sequencing was used, and mtCN measurement was performed by qPCR. It was shown that mtDNA heteroplasmic mutations are characteristic for particular areas of intimal tissue; in 83 intimal samples 55 heteroplasmic variants were found; mean minor allele frequencies level accounted for 0.09, with 12% mean heteroplasmy level. The mtCN variance measured in adjacent areas of intima was high, but atherosclerotic lesions and unaffected intima did not differ significantly in mtCN values. Basing on the ratio of minor and major nucleotide mtDNA variants, we can conclude that there exists the increase in the number of heteroplasmic mtDNA variants, which corresponds to the extent of atherosclerotic morphologic phenotype.

Highlights

The emergence and development of atherosclerotic lesions in the arterial wall are known to occur locally and even focally
The total of 55 cases of heteroplasmy that satisfied all required criteria of selection were found in 27 mitochondrial DNA (mtDNA) positions, with more than 90% of all sequencing reads being mapped on Homo sapiens mitochondrion complete genome sequence
The possibility of somatic origin of mtDNA heteroplasmic variants due to the increased Reactive oxygen species (ROS) production and impaired mitochondrial function supports the hypothesis of accumulation of mutant mtDNA copies during atherogenesis

Summary

Introduction

The emergence and development of atherosclerotic lesions in the arterial wall are known to occur locally and even focally. The alterations in the structure of the mitochondria, mitochondrial dysfunction, and oxidative stress are frequently observed in atherosclerotic lesions [4,5]. Recent studies have confirmed the presence of mtDNA heteroplasmy in various types of human tissues; there are heteroplasmic mutations that are accumulated with ageing [10]. The assessment of mtDNA heteroplasmic mutation load, as well as mtDNA copy number (mtCN) is a plausible way to explain the focality of atherosclerotic lesions [11,12,13,14]. Heteroplasmic mtDNA mutations are of somatic origin, since the activity of mitochondrial function and ROS production vary significantly between different types of tissues [19]; the significant part of heteroplasmic mtDNA mutations, or variants, may be inherited by maternal line [20,21]. Pathogenic mtDNA mutations affect respiratory chain functioning, usually forming the mosaic structure of its deficiency

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