Fig. 1: Experimental design and phylogeny building.

a, The study outline. Blood was sampled from ten sibling pairs who had been the donor and recipient of HCT years previously (range, 9–31 years). CD34⁺ cells were used to seed colonies in culture medium. Single colonies were analysed using WGS (298–430 per pair), and somatic mutations were used to reconstruct phylogenies. Mature cell subsets were sorted using fluorescence-activated cell sorting (FACS) and underwent custom targeted sequencing for the mutations found in WGS. b, Illustrative separate donor-in-donor/donor-in-recipient phylogenies built from samples from each individual from a pair. Branches with putative driver mutations (red dashed lines) are labelled with the variant. Time of HCT is indicated by the grey box. Branch lengths are scaled to chronological time. c, As in b, but combined into a single phylogeny. Branches were found in donor colonies only (cyan), recipient colonies only (pink) or both (black). The heat map shows additional colony-level information. Recip., recipient.