Nature Communications, Published online: 12 September 2026; doi:10.1038/s41467-026-77587-w Somatic mutations in DNMT3A and TET2 are common in age-related clonal haematopoiesis and hematopoietic neoplasms. Here, the authors show that loss of TET2, unlike DNMT3A, makes cells more sensitive to PARP inhibitors by disrupting DNA replication, suggesting TET2 mutations may help predict treatment response.