Human TET2-Mutant Clonal Hematopoiesis Expansion Is Driven by Distinct Inflammatory Signaling Responses in Stem Cells Versus Myeloid Progeny.

Clonal hematopoiesis (CH) increases with age and is associated with severe outcome in the course of infections or tumor development. Understanding the environmental conditions that favor mutant clones and the CH immune system response to such environments is key to designing therapeutic strategies to stall the expansion of mutant clones and the development of CH-associated pathologies. Using human cells, we unravel a cell-specific and opposite impact of TET2 mutations on hematopoietic stem and progenitor cells (HSPC) compared with their myeloid progeny. Multi-omic analyses reveal that TET2-mutant HSPCs exhibit intrinsic epigenetic silencing of AP-1 transcription factors and a blunted transcriptional adaptation to systemic inflammation. Conversely, monocyte-macrophage trajectory derived from TET2Mut hematopoietic stem cells (HSC) contributes to exacerbated inflammation. Together, these findings reconcile how TET2-mutant CH can simultaneously promote increased stemness within the HSPC compartment and heightened inflammation through its myeloid progeny, providing mechanistic insight into how TET2-CH expands under inflammatory stress. SIGNIFICANCE: This study reveals that stress conditions inducing emergency myelopoiesis expand human TET2-mutant clones. TET2 mutation triggers an epigenetic silencing of AP-1 factors contributing to the dampening of the inflammatory responsiveness in TET2mut HSPCs while simultaneously promoting hyperinflammatory TET2mut monocyte-macrophage activation and differentiation, reinforcing inflammation.