H2AX and sarcoma: Measuring across Pot1b−/− sarcoma generations, γ-H2AX TIF formation was undetectable in G1 to G3 Pot1b−/− nuclei but ∼10% of G4 Pot1b−/− nuclei exhibited γ-H2AX TIFs with increasing TIF rates measured with each subsequent generation (Supplementary Figure S5a).