TPO signal for stem cell genomic integrity.

In this issue of Blood, de Laval et al report on a novel mechanism by which hematopoietic stem cells (HSCs) harboring DNA damage are rescued by thrombopoietin (TPO)-mediated DNA repair.1 It has been recently demonstrated that HSCs use the error-prone nonhomologous end-joining (NHEJ) pathway of DNA repair to fix DNA breaks. Maintenance of genomic integrity is crucial for HSC function. Finding the players involved in HSC DNA repair will provide a better understanding of hematopoietic homeostasis, HSC aging, and leukemogenesis.