Extended Data Fig. 5: Mutations versus sampling date.
(a) Mutations attributed to each mutational signature versus sampling date for MarBTN samples. SNVs found in healthy clams, all BTN samples, or LOH regions are excluded prior to analysis to remove founder variants. Results from linear regression of USA samples (n = 5) are shown above each plot, including R squared, p value, mutation rate estimate and the corresponding x-intercept (indicating date the two sub-lineages diverged from one another). PEI samples (n = 3) are included on plots to compare relative mutation counts attributed to each signature but are not included in the linear regression. It is apparent that sig1’mutation counts are higher in PEI, while sig5’ and sig40 mutations are higher in USA. SigS mutations in PEI line up well with the USA sample regression, indicating that sigS mutation rate has stayed stable since the sub-lineages diverged. Points indicate fitting estimate, while error bars indicate 95% confidence interval from signature fitting error. (b) Number of translocations and tandem duplications since the divergence of the sub-lineages, copies of the mitochondrial D-loop, and total Steamer insertions per sample, each plotted against sampling date. Linear regression (blue line) and 95% confidence interval (gray) were calculated for the USA samples (n = 5). No regression was statistically significant. No PEI samples (n = 3) fell within 95% confidence intervals of regression lines, indicating the higher mutation counts in USA samples cannot be explained by the later sampling of USA samples.
