Tissue-specific mitochondrial heteroplasmy at position 16,093 within the same individual

Abstract

Human mitochondrial DNA (mtDNA) research has entered a massively parallel sequencing (MPS) era, providing deep insight into mtDNA genomics and molecular diagnostics. Analysis can simultaneously include coding and control regions, many samples can be studied in parallel, and even minor heteroplasmic changes can be detected. We investigated heteroplasmy using 16 different tissues from three unrelated males aged 40-54 years at the time of death. mtDNA was enriched using two independent overlapping long-range PCR amplicons and analysed by employing illumina paired-end sequencing. Point mutation heteroplasmy at position 16,093 (m.16093T > C) in the non-coding regulatory region showed great variability among one of the studied individuals; heteroplasmy extended from 5.1 % in red bone marrow to 62.0 % in the bladder. Red (5.1 %) and yellow bone marrow (8.9 %) clustered into one group and two arteries and two aortas from different locations into another (31.2-50.9 %), giving an ontogenetic explanation for the formation of somatic mitochondrial heteroplasmy. Our results demonstrate that multi-tissue screening using MPS provides surprising data even when there is a limited number (3) of study subjects and they give reason to speculate that mtDNA heteroplasmic frequency, distribution, and even its possible role in complex diseases or phenotypes seem to be underestimated.

Fig. 1

Full mtDNA amplification and the confirmation of results. a mtDNA was amplified using two overlapping PCR products, blue and red circles. Average coverage density is shown (green). b Position 16,093 heteroplasmy over the SJ600 body panel. c Sequencing coverage in hypervariable region (HVRI) of D-loop. Coverage in the three different tissues of individual SJ600 is shown. d Sanger sequencing confirmation of position 16,093 heteroplasmy. The percentage is from MPS analysis and chromatogram from Sanger sequencing