TET2 Deficiency Increases the Competitive Advantage of Hematopoietic Stem Cells through Upregulation of Thrombopoietin Receptor Signaling

Ten-Eleven Translocation-2 (TET2) mutations drive the expansion of mutant hematopoietic stem cells (HSCs) in clonal hematopoiesis (CH). However, the precise mechanisms by which TET2 mutations confer a competitive advantage to HSCs remain unclear. Here, through an epigenetic drug screen, we discovered that inhibition of disruptor of telomeric silencing 1-like (DOT1L), a H3K79 methyltransferase, selectively reduced the fitness of Tet2 knockout (Tet2KO) hematopoietic stem and progenitor cells (HSPCs). Mechanistically, we found that TET2 deficiency increased H3K79 dimethylation and expression of Mpl, which encodes the thrombopoietin receptor (TPO-R). Correspondingly, TET2 deficiency was associated with a higher proportion of primitive Mpl-expressing (Mpl+) cells in the HSC compartment. Importantly, inhibition of Mpl expression or the signaling downstream of TPO-R was sufficient to reduce the competitive advantage of murine and human TET2-deficient HSPCs. Our findings demonstrate a critical role for aberrant TPO-R signaling in TET2 mutation-driven CH and uncover potential therapeutic strategies against this condition.