Multiomic Profiling of Human Clonal Hematopoiesis Reveals Genotype and Cell-Specific Inflammatory Pathway Activation

Abstract

Clonal hematopoiesis (CH) is an age-associated phenomenon that increases risk for hematologic malignancy and cardiovascular disease. CH is thought to increase cardiovascular disease risk through inflammation in the peripheral blood1. Here, we profile peripheral blood gene expression in 104,566 single cells from a cohort of 17 CH patients and 6 controls. We discovered that patients harboring DNMT3A and TET2 CH mutations at baseline and in response to IL-6 stimulation confer a pro-inflammatory profile to CD14+ monocytes through previously unrecognized pathways including Macrophage Inhibitory Factor (MIF). A germline genetic variant in MIF modifies TET2 CH cardiovascular disease risk. Using mitochondrial lineage tracing, we used a novel method to compare gene expression between mutated and non-mutated cells within individual CH patients. We found that the mutated CH monocytes, but not non-mutated monocytes are pro-inflammatory, explaining why patients with larger CH clones have increased cardiovascular disease risk.

Clonal haematopoiesis across the age spectrum of vasculitis patients with Takayasu’s arteritis, ANCA-associated vasculitis and giant cell arteritis

“…CH mutations were found in affected arteries at similar levels found in peripheral blood, similar to the finding that CH clones can be also detected in atherosclerotic plaques 38. Monocytes from patients with GCA with CH secreted higher levels of chemokines that modulate macrophage proinflammatory signalling pathways (MCP1, MIP1b and MIP1a), findings consistent with recently reported study that identified pathways involved in macrophage function as a mediator of inflammation linked to TET2 mutations in monocytes 37. These chemokines regulate monocyte/macrophage migration from blood across vascular endothelium during immunological surveillance of tissue in response to inflammation, suggesting CH may contribute to vascular inflammation 39 40.…”

“…Our findings support the concept that CH primes myeloid cells to a pro-inflammatory phenotype,37 which potentially may modulate an underlying inflammatory process and alter the course of disease. Patients with GCA with CH had increased myeloid cell burden, and monocytes, NK cells and T lymphocytes displayed an activated phenotype marked by high expression of CD10, CD11b and CD16.…”

“…A recent study demonstrated a 1.48-fold increased risk of incident GCA and TET2-CH 36. Corresponding functional studies of TET2 knockout haematopoietic cells reveal increased myeloid-mediated inflammation in murine models of atherosclerosis and gout 6 33 37. While these studies show an association between CH and various inflammatory diseases, they do not establish causality.…”

Association of Somatic TET2 Mutations With Giant Cell Arteritis

“…8,14 This suggests that the contribution of somatic mutation to GCA may be mediated by myeloid cells, as have emerged in the mechanistic evaluation of a broad array of other TET2-associated conditions. 8 In other model systems, Tet2-deficient monocytes and macrophages display enhanced response to inflammatory stimuli, especially enriched for increased IL-1B and prolonged IL-6 production, [8][9][10]15,16 cytokines well recognized to be elevated in GCA monocytes. 2 More recently, increased proportions of dysregulated immature neutrophils have been described in a humanized mouse model of TET2 CH, which have also been directly implicated in GCA pathogenesis through damage to the endothelium.…”