Thrombopoietin-Increased DNA-PK-Dependent DNA Repair Limits Hematopoietic Stem and Progenitor Cell Mutagenesis in Response to DNA Damage

SummaryDNA double-strand breaks (DSBs) represent a serious threat for hematopoietic stem cells (HSCs). How cytokines and environmental signals integrate the DNA damage response and contribute to HSC-intrinsic DNA repair processes remains unknown. Thrombopoietin (TPO) and its receptor, Mpl, are critical factors supporting HSC self-renewal and expansion. Here, we uncover an unknown function for TPO-Mpl in the regulation of DNA damage response. We show that DNA repair following γ-irradiation (γ-IR) or the action of topoisomerase-II inhibitors is defective in Mpl−/− and in wild-type mouse or human hematopoietic stem and progenitor cells treated in the absence of TPO. TPO stimulates DNA repair in vitro and in vivo by increasing DNA-PK-dependent nonhomologous end-joining efficiency. This ensures HSC chromosomal integrity and limits their long-term injury in response to IR. This shows that niche factors can modulate the HSC DSB repair machinery and opens new avenues for administration of TPO agonists for minimizing radiotherapy-induced HSC injury and mutagenesis.

Graphical AbstractFigure optionsDownload full-size imageDownload high-quality image (259 K)Download as PowerPoint slideHighlights► Mpl loss increases γ-irradiation-induced genomic instability in HSPCs ► TPO promotes DNA repair in vitro and in vivo in HSPCs ► TPO increases DNA-PK activity and NHEJ-mediated repair efficiency in HSPCs ► A single TPO injection before mouse TBI limits long-term HSC injury and mutagenesis