Single-cell sequencing data reveal widespread recurrence and loss of mutational hits in the life histories of tumors

(A) Cell lineage trees of seven cells. (Left) No recurrent mutations; (middle) parallel mutation, a mutation occurs twice in separate lineages, denoted as M₃ and , cells below both occurrences exhibit this mutation; (right) lost mutation, a second occurrence of a mutation in the same lineage brings the genomic site back to the original state, i.e., cells located below do not exhibit this mutation. (B) Mutation trees with attached cell samples. Each tree corresponds to the cell lineage tree in the same column. (C) Mutation matrices with binary states, each corresponds to the mutation tree in the same column. Entry (i,j) contains the expected state of mutation M_i in cell s_j, 0 for absence and 1 for presence in the cell. The red zeros in the matrix on the right are due to the placement of cells s₆ and s₇ below , the second occurrence of mutation M₁, which brings the genomic site back to the original state.