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Objective: The diminished expression of microRNA‐146a (miR‐146a) in systemic lupus erythematosus (SLE) contributes to the aberrant activation of the interferon pathway. Despite its significance, the underlying mechanism driving this reduced expression remains elusive. Considering the integral role of enhancers in steering gene expression, our study seeks to pinpoint the SLE‐affected enhancers responsible for modulating miR‐146a expression. Additionally, we aim to elucidate the mechanisms by which these enhancers influence the contribution of miR‐146a to the activation of the interferon pathway. Methods: Circular chromosome conformation capture sequencing and epigenomic profiles were applied to identify candidate enhancers of miR‐146a. CRISPR activation was performed to screen functional enhancers. Differential analysis of chromatin accessibility was used to identify SLE‐dysregulated enhancers, and the mechanism underlying enhancer dysfunction was investigated by analyzing transcription factor binding. The therapeutic value of a lupus‐related enhancer was further evaluated by targeting it in the peripheral blood mononuclear cells (PBMCs) of patients with SLE through a CRISPR activation approach. Results: We identified shared and cell‐specific enhancers of miR‐146a in distinct immune cells. An enhancer 32.5 kb downstream of miR‐146a possesses less accessibility in SLE, and its chromatin openness was negatively correlated with SLE disease activity. Moreover, CCAAT/enhancer binding protein α, a down‐regulated transcription factor in patients with SLE, binds to the 32.5‐kb enhancer and induces the epigenomic change of this locus. Furthermore, CRISPR‐based activation of this enhancer in SLE PBMCs could inhibit the activity of interferon pathway. Conclusion: Our work defines a promising target for SLE intervention. We adopted integrative approaches to define cell‐specific and functional enhancers of the SLE critical gene and investigated the mechanism underlying its dysregulation mediated by a lupus‐related enhancer. [ABSTRACT FROM AUTHOR]

Objective: Disruption of B cell homeostasis and subsequent dominance of effector B cell subsets are critical for the development of systemic lupus erythematosus (SLE). Revealing the key intrinsic regulators involved in the homeostatic control of B cells has important therapeutic value for SLE. This study was undertaken to determine the regulatory role of the transcription factor Pbx1 in B cell homeostasis and lupus pathogenesis. Methods: We constructed mice with B cell–specific deletion of Pbx1. T cell–dependent and T cell–independent humoral responses were induced by intraperitoneal injection of nitrophenyl‐containing hapten (NP) conjugated to keyhole limpet hemocyanin or NP‐Ficoll. The regulatory effects of Pbx1 on autoimmunity were observed in a Bm12‐induced lupus murine model. We investigated mechanisms of Pbx1 using RNA sequencing, the cleavage under targets and tagmentation assay, and chromatin immunoprecipitation–quantitative polymerase chain reaction assay. We transduced B cells from SLE patients with plasmids that overexpressed PBX1 to explore the in vitro therapeutic efficacy of PBX1. Results: Pbx1 was specifically down‐regulated in autoimmune B cells and negatively correlated with disease activity. The deficiency of Pbx1 in B cells resulted in excessive humoral responses following immunization. In the Bm12‐induced lupus model, mice with B cell–specific Pbx1 deficiency displayed enhancements in germinal center responses, plasma cell differentiation, and autoantibody production. Pbx1‐deficient B cells had increased survival and proliferative advantages after activation. Pbx1 regulated genetic programs by directly targeting critical components of the proliferation and apoptosis pathways. In SLE patients, PBX1 expression was negatively correlated with effector B cell expansion; when PBX1 expression was enforced, the survival and proliferative capacity of SLE B cells were attenuated. Conclusion: Our study reveals the regulatory function and mechanism of Pbx1 in adjusting B cell homeostasis and highlights Pbx1 as a therapeutic target in SLE. [ABSTRACT FROM AUTHOR]

Objective: Emerging evidence indicates that a distinct CD11c+T‐bet+ B cell subset, termed age/autoimmune‐associated B cells (ABCs), is the major pathogenic autoantibody producer in lupus. Human lupus is associated with significant metabolic alterations, but how ABCs orchestrate their typical transcription factors and metabolic programs to meet specific functional requirements is unclear. We undertook this study to characterize the metabolism of ABCs and to identify the regulators of their metabolic pathways in an effort to develop new therapies for ABC‐mediated autoimmunity. Methods: We developed a T‐bet–tdTomato reporter mouse strain to trace live T‐bet+ B cells and adoptively transferred CD4+ T cells from bm12 mice to induce lupus. We next sorted CD11c+tdTomato+ B cells and conducted RNA sequencing and an extracellular flux assay. A metabolic restriction to constrain ABC formation was tested in human and mouse B cells. We used a bm12‐induced lupus mouse model to conduct the metabolic intervention. Results: ABCs exhibited a hypermetabolic state with enhanced glycolytic capacity. The increased glycolytic rate in ABCs was promoted by interferon‐γ (IFNγ) signaling. T‐bet, a downstream transcription factor of IFNγ, regulated the gene program of the glycolysis pathway in ABCs by repressing the expression of Bcl6. Functionally, glycolysis restriction could impair ABC formation. The engagement of glycolysis promoted survival and terminal differentiation of antibody‐secreting cells. Administration of a glycolysis inhibitor ameliorated ABC accumulation and autoantibody production in the lupus‐induced bm12 mouse model. Conclusion: T‐bet can couple immune signals and metabolic programming to establish pathogenic ABC formation and functional capacities. Modulation of ABCs favored a metabolic program that could be a novel therapeutic approach for lupus. [ABSTRACT FROM AUTHOR]

Objective: Increased Toll‐like receptor 7 (TLR‐7) signaling leading to the production of type I interferon (IFN) is an important contributor to human systemic lupus erythematosus (SLE). Protein kinase C and casein kinase substrate in neurons 1 (PACSIN1), a molecule that regulates synaptic vesicle recycling, has been linked to TLR‐7/TLR‐9–mediated type I IFN production in humans and mice, but the underlying mechanism is unknown. We undertook this study to explore the pathogenicity and underlying mechanism of a de novo PACSIN1 missense variant identified in a child with SLE. Methods: PACSIN1 Q59K de novo and null variants were introduced into a human plasmacytoid dendritic cell line and into mice using CRISPR/Cas9 editing. The effects of the variants on TLR‐7/TLR‐9 signaling in human and mouse cells, as well as PACSIN1 messenger RNA and IFN signature in SLE patients, were assessed using real‐time polymerase chain reaction and flow cytometry. Mechanisms were investigated using luciferase reporter assays, RNA interference, coimmunoprecipitation, and immunofluorescence. Results: We established that PACSIN1 forms a trimolecular complex with tumor necrosis factor receptor–associated factor 4 (TRAF4) and TRAF6 that is important for the regulation of type I IFN. The Q59K mutation in PACSIN1 augments binding to neural Wiskott‐Aldrich syndrome protein while it decreases binding to TRAF4, leading to unrestrained TRAF6‐mediated activation of type I IFN. Intriguingly, PACSIN1 Q59K increased TLR‐7 but not TLR‐9 signaling in human cells, leading to elevated expression of IFNβ and IFN‐inducible genes. Untreated SLE patients had high PACSIN1 expression in peripheral blood cells that correlated positively with IFN‐related genes. Introduction of the Pacsin1 Q59K mutation into mice caused increased surface TLR‐7 and TRAIL expression in B cells. Conclusion: PACSIN1 Q59K increases IFNβ activity through the impairment of TRAF4‐mediated inhibition of TLR‐7 signaling, possibly contributing to SLE risk. [ABSTRACT FROM AUTHOR]

Objective: IRF5 plays a crucial role in the development of lupus. Genome‐wide association studies have identified several systemic lupus erythematosus (SLE) risk single‐nucleotide polymorphisms (SNPs) enriched in the IRF5 locus. However, no comprehensive genome editing–based functional analysis exists to establish a direct link between these variants and altered IRF5 expression, particularly for enhancer variants. This study was undertaken to dissect the regulatory function and mechanisms of SLE IRF5 enhancer risk variants and to explore the utilization of clustered regularly interspaced short palindromic repeat interference (CRISPRi) to regulate the expression of disease risk gene to intervene in the disease. Methods: Epigenomic profiles and expression quantitative trait locus analysis were applied to prioritize putative functional variants in the IRF5 locus. CRISPR‐mediated deletion, activation, and interference were performed to investigate the genetic function of rs4728142. Allele‐specific chromatin immunoprecipitation–quantitative polymerase chain reaction and allele‐specific formaldehyde‐assisted isolation of regulatory element–quantitative polymerase chain reaction were used to decipher the mechanism of alleles differentially regulating IRF5 expression. The CRISPRi approach was used to evaluate the intervention effect in monocytes from SLE patients. Results: SLE risk SNP rs4728142 was located in an enhancer region, indicating a disease‐related regulatory function, and risk allele rs4728142‐A was closely associated with increased IRF5 expression. We demonstrated that an rs4728142‐containing region could act as an enhancer to regulate the expression of IRF5. Moreover, rs4728142 affected the binding affinity of zinc finger and BTB domain–containing protein 3 (ZBTB3), a transcription factor involved in regulation. Furthermore, in monocytes from SLE patients, CRISPR‐based interference with the regulation of this enhancer attenuated the production of disease‐associated cytokines. Conclusion: These results demonstrate that the rs4728142‐A allele increases the SLE risk by affecting ZBTB3 binding, chromatin status, and regulating IRF5 expression, establishing a biologic link between genetic variation and lupus pathogenesis. [ABSTRACT FROM AUTHOR]

Objective: Increasing evidence indicates that the cyclic GMP‐AMP synthase/stimulator of interferon genes (cGAS/STING) signaling pathway has a critical pathogenic role in systemic lupus erythematosus (SLE). Expression levels of the interferon (IFN)–inducible gene IFIT3 are elevated in SLE patients. However, it is still not clear how IFIT3 contributes to the pathogenesis of SLE. This study was undertaken to investigate the activation of the cGAS/STING signaling pathway in human SLE monocytes, and to determine how elevated expression of IFIT3 could contribute to overactive cGAS/STING signaling in patients with SLE. Methods: Monocytes from SLE patients or healthy controls were examined for activity of the cGAS/STING signaling pathway and expression levels of IFIT3. Correlations between cGAS/STING signaling activity and SLE clinical features were analyzed. Gain‐ or loss‐of‐function experiments were used to determine the role of IFIT3 in cGAS/STING signaling. Coimmunoprecipitation assays were used to identify the interaction between IFIT3 and other proteins. Results: The cGAS/STING signaling pathway was found to have enhanced activity in monocytes from SLE patients compared to healthy controls, as indicated by the higher expression of IFNβ downstream. Levels of IFIT3 were significantly elevated in human SLE monocytes, and this was positively correlated with the activity of the cGAS/STING signaling pathway. In vitro, the expression of VACV70‐induced IFNβ was reduced by knockdown of IFIT3, whereas overexpression of IFIT3 produced an opposite effect. Finally, IFIT3 was found to interact with both STING and TANK‐binding kinase 1. Conclusion: These findings suggest that IFIT3 is one of the genes that contributes to the overactive cGAS/STING signaling pathway in human SLE monocytes. IFIT3 may therefore serve as a novel therapeutic target for blocking the production of type I IFN and other proinflammatory cytokines by the cGAS/STING signaling pathway in patients with SLE. [ABSTRACT FROM AUTHOR]