The opposing effect of TET2-derived clonal hematopoiesis in stemness and immunity

The expansion of HSC clones and their immune progeny carrying somatic mutations is defined as clonal hematopoiesis (CH) with its prevalence increasing with age. Individuals with CH are at higher risk of developing hematological malignancies but also other pathologies, such as cardiovascular or inflammatory pulmonary diseases. Understanding which environmental conditions 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. In this work, we characterized how mutations in TET2, one of the most frequent in CH, increase the competitive advantage of human HSCs upon environmental stress conditions and at the same time shape the immune response of their myeloid progeny. Employing a humanized mouse model, we show that environmental conditions that drive emergency myelopoiesis promote human TET2-derived CH. We unravel an opposite and cell-specific impact of TET2 mutations on HSCs and their myeloid progeny to inflammatory stress. In such environments, TET2Mut HSCs have a mitigated transcriptional upregulation of inflammatory pathways, and by contrast, TET2Mut myeloid cells have an exacerbated inflammatory response. A distinct monocyte-macrophage trajectory derived from TET2Mut HSCs contributes to pathological inflammation. These findings provide evidence at the human cell level and reconcile the notion that TET2-derived CH is associated with both increased stemness at the HSC compartment and promoted inflammatory environments from the myeloid progeny. Overall design: We performed single cell RNA sequencing in human TET2-WT and TET2-Mut hematopoietic stem and progenitor cells and immune cells isolated from bone marrow of humanised mice after a regimen of LPS injections to induce systemic inflammation.