Fig. 4

Non Synonomous and synonomous somatic heteroplasmic count and heteroplasmic fractions stratified by locus. Upper Left: Strip chart showing the heteroplasmy (HF > 0.02/< 0.98) counts per cell per sample after normalisation by locus length (total region bp lengths: D-loop = 1124, rRNA = 2511, tRNA = 1486 and Protein Coding = 11,382). There was a significant increase in non-synonymous variant counts across all 13 individuals (Mann Whitney U, p < 0.001). Upper Right: Strip chart showing the distribution of protein-coding variant heteroplasmy fractions (HF > 0.02/< 0.98) after stratification into non-synonymous and synonymous variants. We observed no significant difference in HF between non-synonymous and synonymous variants (Mann Whitney U, p > 0.05). Lower left: Histogram of MutPred⁵⁷ and APOGEE 2⁵⁸ scores showing a significant skew towards pathogenicity (MutPred score > 0.50⁵⁷, Kurtosis = 3.17, Shapiro-Wilks Normality Test p < 0.001 and APOGEE 2 score > 0.38⁵⁸, Kurtosis = 1.57, Shapiro-Wilks Normality Test p < 0.001). Dotted red lines indicate MutPred and APOGEE thresholds (0.5 and 0.38 respectively). Lower right: Boxplots of MSC somatic heteroplasmic MutPred and APOGEE 2 scores indicating that the majority of samples harbour cells with potentially pathogenic variants (MutPred⁵⁷ pathogenic = 949 variants or 82% and APOGEE 2⁵⁸ = pathogenic 593 or 51%).