Extended Data Fig. 3: Raw mutational spectra and de novo extracted mutational signatures.
(a) Plots show the mutational probability of SNVs in all trinucleotide contexts that were identified in various samples after filtering. Trinucleotide order is the same as shown in Fig. 2. Healthy clam SNVs (black labels - top) refer to SNVs that were unique to that clam and not found in other clams, resulting in no overlap of SNVs but still very similar spectra. SNVs found in all BTN samples (gray labels – upper middle) are divided into those found in a healthy clam (likely all from the founder clam genome) and those not found in any of the three healthy clams (includes a mixture of founder and early somatic mutations). Likely somatic SNVs found within the USA (blue labels) and PEI (red labels) sub-lineages show those SNVs that are either shared between all samples (Fig. 2a - not shown here), multiple samples (lower middle), or unique to individual samples (bottom). SNVs found in All mutational probabilities are corrected for mutational opportunities in the clam genome, and total mutation counts in each image are shown in the label. (b) We performed de novo mutational signature extraction to identify trinucleotide SNV differences between the various samples in this study, yielding four mutational signatures with mutational probabilities corrected for mutational opportunities in the clam genome. Error bars display 95% confidence intervals as determined by the extraction software, sigfit. Signatures sig1’, sig5’ and sig40’ are named after the closest signature in the COSMIC database, as determined by cosine similarity. SigS was named to reflect that it was specific to Somatic mutations in cancer samples.
