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DNMT3A and TET2 restrain mitochondrial DNA-mediated interferon signaling in macrophages

ABSTRACT: Deleterious somatic mutations in DNMT3A or TET2 are associated with clonal expansion of haematopoietic cells and higher risk of cardiovascular disease (CVD). In mice, most studies have indicated an over-activation of the inflammatory program in myeloid cells with reduced DNMT3A or TET2 expression. However, the effect of loss of function of DNMT3A and TET2 in human myeloid cells remains poorly understood. Here, we investigated the roles of DNMT3A and TET2 in normal human monocyte- derived macrophages (mDM), in mDM isolated from individuals with DNMT3A or TET2 mutations and in macrophages isolated from human atherosclerotic plaques. Using a combination of transcriptomic, epigenetic, and imaging assays, we provide evidence that, in addition to distinct roles in regulation of macrophage gene expression, DNMT3A and TET2 share a common role in maintaining mitochondrial DNA integrity by regulating the expression of Transcription Factor A, Mitochondria ( TFAM ). This shared function is dependent on interactions of DNMT3A and TET2 with RBPJ and ZNF143 at regulatory elements in the TFAM gene. Experimental reduction of DNMT3A or TET2 expression in normal human mDMs results in downregulation of TFAM, release of mtDNA into the cytoplasm and consequent activation of a type I interferon response mediated by cGAS. Single-cell RNA-seq analysis of mDMs from individuals with heterozygous loss-of-function mutations in DNMT3A and TET2 revealed a similar transcriptional signature. In addition, single-cell RNA-seq analysis of normal mDM and macrophages residing in human atherosclerotic plaques revealed higher expression of type I IFN signature genes specifically in cells with lower DNMT3A or TET2 expression. The production of IFN as a component of the type I IFN response induces activation of interferon-stimulated genes in neighbouring cells, representing a mechanism by which partial loss of function of DNMT3A or TET2 in a small fraction of cells could exert pathogenic effects in the artery wall. These findings suggest that targeting the type I IFN pathway may have therapeutic value in reducing risk of cardiovascular disease in patients with DNMT3A or TET2 mutations.

ORGANISM(S): Homo sapiens

PROVIDER: GSE206030 | GEO | 2022/08/05

REPOSITORIES: GEO

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Project description:Purpose Immune reactions following corneal transplantation are the most common cause of transplant failure. However, the underlying mechanisms of corneal graft rejection are not yet fully understood but increasing evidence points to a crucial role of the innate immune system in this context. Using a human in vitro model, we aimed to assess the response of human macrophages to stimulation with human corneal tissue and whether corneal endothelial cells (CEC) have immune-modulating properties. Methods Human monocytes were isolated from peripheral blood mononuclear cells (PBMC) and differentiated into monocyte-derived macrophages (MDM). A standardized protocol was used for disintegration of human corneas into fragments of defined sizes. MDMs were stimulated using processed corneal material with or without CEC. Lipopolysaccharide (LPS) or interferon-gamma (IFNγ) served as controls. RNA sequencing was applied to analyze the impact of differential stimulation of MDMs on their transcriptional profile. Results The transcriptional profile of MDMs was significantly modulated by the type of stimulus used for MDM activation as well as by the individual donor. LPS- or IFNγ-stimulation resulted in distinct transcriptional alterations compared to unstimulated MDMs including an upregulation of various cytokines such as CXCL9 and CCL3, 4, 5 and 19. Corneal tissue induced the differential expression of 45 genes when compared to unstimulated MDMs, with several metallothioneins (MTs) among the upregulated factors (MT1A, MT1E, MT1F, MT1G, MT1H, MT1L, MT1M, MT1X, MT2A). This effect was independent of the presence or absence of CEC. Conclusions The MDM in vitro model proved to be a robust tool to study the effects of LPS, IFNγ and corneal tissue homogenates on the transcriptional activity of MDM. Human macrophages showed a distinct upregulation of various MTs when challenged with human corneal allogen with or without corneal endothelium, which might have an immune-modulatory effect. As a general observation, it appears that in MDM-based studies a significant donor-dependent effect on the transcriptional profile of MDMs needs to be considered and adjusted before downstream analysis.

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DNMT3A and TET2 restrain mitochondrial DNA-mediated interferon signaling in macrophages

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