A specific IFIH1 gain-of-function mutation causes Singleton-Merten syndrome

Cardiodermatology: the heart of the connection between the skin and cardiovascular disease

The skin and cardiovascular systems are connected in unique and meaningful ways, and many diseases conventionally considered as being limited to one organ system are more closely related than previously believed. Major cardiovascular diseases and phenomena such as infective endocarditis, congestive heart failure, Kawasaki disease and thromboembolism are associated with specific skin findings, and advances in genetics, immunology and clinical epidemiology show that inflammatory dermatological diseases, such as psoriasis, have serious cardiovascular and cardiometabolic consequences. Additionally, commonly used cardiovascular therapies, such as antihypertensive medications, are associated with important cutaneous adverse effects, including photosensitivity, photocarcinogenesis and eczematous skin reactions. Moreover, systemic dermatological therapies, including retinoids, Janus kinase inhibitors and biologics, can alter the risk of cardiovascular and cardiometabolic diseases. In this Review on cardiodermatology, we provide interdisciplinary insights from dermatology and cardiology that will be of practical use to both cardiologists and generalists who manage cardiovascular and cardiometabolic diseases in patients with dermatological findings or histories. We discuss specific skin findings associated with cardiovascular diseases to aid in diagnosis; important cutaneous adverse effects of common cardiovascular therapies, for the purpose of treatment monitoring; and the effect of dermatological diseases and dermatological treatment on cardiovascular risk.

Cell-Autonomous Immunity: From Cytosolic Sensing to Self-Defense

As an evolutionarily conserved and ubiquitous mechanism of host defense, non-immune cells in vertebrates possess the intrinsic ability to autonomously detect and combat intracellular pathogens. This process, termed cell-autonomous immunity, is distinct from classical innate immunity. In this review, we comprehensively examine the defense mechanisms employed by non-immune cells in response to intracellular pathogen invasion. We provide a detailed analysis of the cytosolic sensors that recognize aberrant nucleic acids, lipopolysaccharide (LPS), and other pathogen-associated molecular patterns (PAMPs). Specifically, we elucidate the molecular mechanisms underlying key signaling pathways, including the cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) pathway, the retinoic acid-inducible gene I (RIG-I)-like receptors (RLRs)-mitochondrial antiviral signaling (MAVS) axis, and the guanylate-binding proteins (GBPs)-mediated pathway. Furthermore, we critically evaluate the involvement of these pathways in the pathogenesis of various diseases, including autoimmune disorders, inflammatory conditions, and malignancies, while highlighting their potential as therapeutic targets.

Overlapping Aicardi-Goutières and Singleton-Merten syndromes with a heterozygous gain-of-function mutation in IFIH1 mimicking juvenile idiopathic arthritis

Aicardi-Goutières syndrome (AGS) and Singleton-Merten syndrome (SMS) are associated with heterozygous gain-of-function mutations in the interferon induced with helicase C domain 1 (IFIH1) gene. Recent reports describe patients exhibiting overlapping clinical features of AGS and SMS, along with marked type I interferon (IFN) overproduction. However, the clinical characteristics and optimal treatment strategies remain unclear. Herein, we present a patient with overlapping clinical features of AGS and SMS who was initially misdiagnosed with juvenile idiopathic arthritis. Surgical soft tissue release of the hip and knee joints improved joint deformities and spastic paraparesis. Baricitinib effectively treated refractory chilblains and skin ulcers while reducing IFN-stimulated gene overexpression in peripheral blood. These findings indicate that baricitinib may be a safe and effective treatment for AGS-SMS overlap, and surgical intervention may be a viable option for refractory joint deformities with spastic paraparesis.

Generation of iPSCs line from patient with Singleton-Merten syndrome

Singleton-Merten syndrome (SMS) is a rare genetic condition associated with abnormal calcification and skeletal anomalies. To explore the underlying mechanisms of this disorder, we generated induced pluripotent stem cells (iPSCs) from the blood cells of a patient with SMS. The iPSCs retain the genetic mutation linked to the syndrome, making them a relevant model for studying disease-specific processes. These cells display all key features of pluripotent stem cells, including the expression of characteristic markers, the ability to differentiate into cell types from all three germ layers, and stable growth during passaging. These iPSCs provide a valuable tool for investigating the processes involved in SMS, particularly those leading to abnormal calcification. They also offer a platform for testing potential therapeutic strategies aimed at addressing SMS-related complications. Future work will focus on directing these cells into specific cell types to better understand the pathways involved in the disease and identify possible treatment targets. This study highlights the potential of patient-derived iPSCs for advancing research into rare genetic disorders.

Dissecting the molecular landscape of Parkinson's disease and Parkinson's disease dementia using highly efficient snRNA-seq (HIF-snRNA-seq)

This study presents a transcriptomic analysis of the cingulate cortex (CING) in Parkinson's disease (PD) and Parkinson's disease dementia (PDD) using a High-efficiency single-nucleus RNA sequencing (HiF-snRNA-seq) protocol optimized for post-mortem brain samples. RNA quality prediction, poly-A tailing, and dCas9-targeted depletion enabled analysis of 77 high-quality samples from 240 cases, yielding over 2 million nuclei classified into seven major cell types. Disease conditions revealed altered astrocyte and microglia proportions, implicating their roles in neuroinflammation. Differential expression analysis identified unique and shared genes across PD and PDD, linked to synaptic remodeling, stress responses, and inflammation. Stage-specific analysis uncovered tau-dependent early-stage genes and inflammation-associated late-stage genes. This study highlights the CING's central role in PD and PDD pathophysiology, offering insights into disease mechanisms and identifying candidate genes and pathways for therapeutic and biomarker development.

Short-term efficacy of tofacitinib, a JAK inhibitor, in IFIH1-related Aicardi-Goutières syndrome

Aicardi-Goutières syndrome (AGS) is a genetically heterogeneous type-I interferonopathy presenting in infancy with intracranial calcifications, white matter lesions, and brain atrophy. AGS7, caused by gain-of-function (GOF) mutations in the IFIH1 gene, triggers excessive type-I interferon production, leading to autoimmune responses. We describe an 18-year-old female diagnosed with AGS7 due to a somatic GOF mutation in IFIH1. In 2014, she presented with multiple joint swelling, facial rash, and hair loss, and received a diagnosis of juvenile idiopathic arthritis and systemic lupus erythematosus. Traditional immunosuppressants were administered, but provided little benefit. Genetic testing in 2023 revealed a GOF variant (p.R720G) in IFIH1. Given the link between IFIH1 variants and the Janus kinase (JAK)-signal transducer and activator of transcription (STAT) pathway, we administered tofacitinib (a JAK inhibitor) and oral methylprednisolone, with tapering of the traditional immunosuppressants. After nearly one year, the patient showed no significant disease activity and normal hair growth, with no notable changes in thyroid function. Although treatment of AGS remains challenging, this case suggests tofacitinib can successfully manage AGS7 symptoms. More clinical studies are needed to verify the long-term safety and efficacy of tofacitinib.

Overlap Diagnostic Odyssey and Full Mouth Rehabilitation of a Juvenile Patient With IFIH1-Related Disorder: A Case of Aicardi-Goutières and Singleton Merten Syndromes Overlap

OBJECTIVE

This case report describes the prosthetic rehabilitation of a 15-year-old female patient with a rare IFIH1-related interferonopathy, presenting features from both Aicardi-Goutières Syndrome (AGS) and Singleton-Merten Syndrome (SMS). The report highlights the unique dental and maxillofacial challenges, and the multidisciplinary treatment approach required in such patients.

METHODS

The patient underwent a comprehensive prosthetic rehabilitation, which included two stages of extractions, followed by the fabrication of a complete upper denture and a two-implant-retained mandibular overdenture. Pre- and post-treatment assessments, including panoramic radiographs and cone beam computed tomography (CBCT), were utilized to guide treatment.

RESULTS

Initial assessments revealed root formation anomalies, multiple impacted teeth, internal resorption, and associated dental anomalies. Following extractions and ridge augmentation, two freestanding implants were successfully placed in the anterior mandible, with no complications during osseointegration. The patient reported satisfaction with the function, esthetics, and stability of her dental prostheses.

CONCLUSIONS

This case underscores the importance of a multidisciplinary approach for managing dental anomalies and bone fragility in patients with IFIH1-related disorders. Early genetic diagnosis and thorough treatment planning are critical for successful prosthetic rehabilitation and optimal patient outcomes.

GWAS meta-analysis of psoriasis identifies new susceptibility alleles impacting disease mechanisms and therapeutic targets

Psoriasis is a common, debilitating immune-mediated skin disease. Genetic studies have identified biological mechanisms of psoriasis risk, including those targeted by effective therapies. However, the genetic liability to psoriasis is not fully explained by variation at robustly identified risk loci. To refine the genetic map of psoriasis susceptibility we meta-analysed 18 GWAS comprising 36,466 cases and 458,078 controls and identified 109 distinct psoriasis susceptibility loci, including 46 that have not been previously reported. These include susceptibility variants at loci in which the therapeutic targets IL17RA and AHR are encoded, and deleterious coding variants supporting potential new drug targets (including in STAP2, CPVL and POU2F3). We conducted a transcriptome-wide association study to identify regulatory effects of psoriasis susceptibility variants and cross-referenced these against single cell expression profiles in psoriasis-affected skin, highlighting roles for the transcriptional regulation of haematopoietic cell development and epigenetic modulation of interferon signalling in psoriasis pathobiology.

ADAR1 haploinsufficiency and sustained viral RdRp dsRNA synthesis synergize to dysregulate RNA editing and cause multi-system interferonopathy

Sensing of viral double-stranded RNA by MDA5 triggers abundant but transient interferon-stimulated gene (ISGs) expression. If dsRNA synthesis is made persistent by transgenically expressing a picornaviral RNA-dependent RNA polymerase (RdRp) in mice, lifelong MDA5 activation and marked, global ISG upregulation result. This confers robust protection from viral diseases but in contrast to numerous other chronic MDA5 hyperactivation states, the mice suffer no autoimmune consequences. Here we find they further confound expectations by being resistant to a strong autoimmunity (lupus) provocation. However, knockout of one allele of Adar , which by itself is also well-tolerated, breaks the protective state and results in a severe disease that resembles interferonopathies caused by MDA5 gain-of-function mutations. In Adar +/- RdRp transgenic mice, A-to-I editing is both dysregulated and increased (numbers of genes and sites). This dsRNA-driven, MDA5-wild type model establishes that viral polymerase-sourced dsRNA can drive interferonopathy pathogenesis and illuminates the autoimmunity preventing role of ADAR1, while the ADAR1-intact viral RdRp model distinctively uncouples chronic MDA5 hyperactivity and autoinflammatory disease.

DAMPs, PAMPs, NLRs, RIGs, CLRs and TLRs - Understanding the Alphabet Soup in the Context of Bone Biology

PURPOSE OF REVIEW

The purpose of this review is to summarize the current understanding of cell-autonomous innate immune pathways that contribute to bone homeostasis and disease.

RECENT FINDINGS

Germ-line encoded pattern recognition receptors (PRRs) are the first line of defense against danger and infections. In the bone microenvironment, PRRs and downstream signaling pathways, that mount immune defense, interface intimately with the core cellular processes in bone cells to alter bone formation and resorption. The role of PRR engagement on bone remodeling has been best described as a result of activated macrophages secreting effector molecules that reshape the characteristics of bone-resident cells. However, it is being increasingly recognized that local bone resident-cells like osteoclasts and osteoblasts possess an arsenal of PRRs. The engagement of these PRRs by stimuli in the bone niche can drive cell-autonomous (aka cell-intrinsic) responses that, in turn, impact bone-remodeling dramatically, irrespective of immune cell effectors. Indeed, this vital role for cell-autonomous innate immune responses is evident in how reduced PRR activity within osteoclast progenitors correlates with their reduced differentiation and abnormal bone remodeling. Further, cell-intrinsic PRR activity has now been shown to influence the behavior of osteoblasts, osteocytes and other local immune/non-immune cell populations. However, distinct PRR families have varying impact on bone homeostasis and inflammation, emphasizing the importance of investigating these different nodes of innate immune signaling in bone cells to better identify how they synergistically and/or antagonistically regulate bone remodeling in the course of an immune response. Innate immune sensing within bone resident cells is a critical determinant for bone remodeling in health and disease.

Established and Emerging Roles of DEAD/H-Box Helicases in Regulating Infection and Immunity

The sensing of nucleic acids by DEAD/H-box helicases, specifically retinoic acid-inducible gene I (RIG-I) and melanoma differentiation-associated protein 5 (MDA5), plays a critical role in inducing antiviral immunity following infection. However, this DEAD/H-box helicase family includes many additional proteins whose immune functions have not been investigated. While numerous DEAD/H-box helicases contribute to antiviral immunity, they employ diverse mechanisms beyond the direct sensing of nucleic acids. Some members have also been identified to play proviral (promoting virus replication/propagation) roles during infections, regulate other non-viral infections, and contribute to the regulation of autoimmunity and cancer. This review synthesizes the known and emerging functions of the broader DEAD/H-box helicase family in immune regulation and highlights ongoing efforts to target these proteins therapeutically.

Exploring emerging JAK inhibitors in the treatment of Aicardi-Goutières syndrome

INTRODUCTION

Aicardi-Goutières syndrome (AGS) is a genetically heterogeneous monogenic autoinflammatory disorder classified as an 'interferonopathy'. Nine genes have been implicated in AGS, encoding proteins involved in nucleic acid clearance, repair, sensing, or histone pre-mRNA processing. Dysregulation in these pathways leads to excessive type I interferon production, the primary driver of the disease. AGS typically presents with early-life neurological regression, followed by stabilization with varying degrees of neurological impairment and common extra-neurological features, such as chilblains. Advances in understanding AGS pathogenesis have enabled the development of new therapies, with JAK inhibitors emerging as the most studied option for reducing interferon-mediated effects.

AREAS COVERED

This review discusses the clinical features, genetic basis, and molecular pathways of AGS while tracing the evolution of its therapeutic strategies. Particular emphasis is placed on JAK inhibitors, which target proteins activated by type I interferons, providing a novel direction in treatment.

EXPERT OPINION

Inhibitors effectively reduce extra-neurological symptoms in AGS, though their impact on neurological outcomes remains unclear. The unknown natural history of AGS limits treatment evaluation. Despite growing insights, key aspects of pathogenesis and treatment optimization - including timing, administration, and long-term effects - remain unresolved, highlighting the need for further research.

Sterile activation of RNA-sensing pathways in autoimmunity

RNA-sensing pathways play a pivotal role in host defense against pathogenic infections to maintain cellular homeostasis. However, in the absence of infection, certain endogenous RNAs can serve as the activators of RNA-sensing pathways as well. The inappropriate activation of RNA-sensing pathways by self-ligands leads to systemic inflammation and autoimmune diseases. In this review, we summarize current findings on the sterile activation of RNA sensors, as well as its implications in autoimmunity, inflammatory diseases, and therapeutics.

Mouse models of type I interferonopathies

Type I interferonopathies are severe monogenic diseases caused by mutations that result in chronically upregulated production of type I interferon. They present with a broad variety of symptoms, the mechanisms of which are being extensively studied. Mouse models of type I interferonopathies are an important resource for this purpose, and in this context, we review several key molecular and phenotypic findings that are advancing our understanding of the respective diseases. We focus on genotypes related to nucleic acid metabolism, sensing by cytosolic receptors and downstream signalling.

E3 ubiquitin ligase ANKIB1 attenuates antiviral immune responses by promoting K48-linked polyubiquitination of MAVS

Upon sensing cytosolic viral RNA, retinoic acid-inducible gene-I-like receptors (RLRs) interact with mitochondrial antiviral signaling proteins (MAVSs) to activate IRF3 and nuclear factor κB (NF-κB) signaling, initiating innate immune responses. Thus, RLR activation plays a vital role in the removal of invasive RNA viruses while maintaining immune homeostasis. However, inadequate or excessive activation of immunity can cause harm and can even lead to lethal consequences. In this study, we identify an E3 ligase, ankyrin repeat and IBR domain containing 1 (ANKIB1), which suppresses RLR signaling via MAVS. ANKIB1 binds to MAVS to enhance K48-linked polyubiquitination with K311R, causing proteasomal degradation of MAVS. Deficiency of ANKIB1 significantly increases the RLR-mediated production of type I interferon (IFN) along with pro-inflammatory factors. Consequently, ANKIB1 deficiency remarkably increases antiviral immunity and decreases viral replication in vivo. Therefore, we reveal that ANKIB1 restricts RLR-induced innate immune activation, indicating its potential role as a therapeutic target for viral infections.

ZIKV induces P62-mediated autophagic degradation of TRAF6 through TRAF6-NS1 interaction

Tumor necrosis factor receptor-associated factor 6 (TRAF6) is crucial in flavivirus infections, modulating the host immune response through interactions with viral proteins. Despite its importance, the relationship between TRAF6 and Zika virus (ZIKV) remains poorly understood. Our prior proteomics analysis revealed reduced TRAF6 protein levels in ZIKV-infected human trophoblast cells compared to non-infected controls. Subsequent studies in cell models and murine tissues confirmed a significant reduction in both TRAF6 mRNA and protein levels post-ZIKV infection. Further investigations unveiled that ZIKV induces P62-mediated degradation of TRAF6, with NS1 identified as the primary contributor. Co-localization and interaction studies demonstrated that NS1 promotes the association of P62, a key autophagy mediator, with TRAF6. Notably, our findings revealed TRAF6 enhances ZIKV infection, NS1 ubiquitination, NS1 expression, and the production of inflammatory cytokines and chemokines. These insights highlight the intricate TRAF6-ZIKV relationship, offering potential for drug targeting NS1-TRAF6 interactions to manage ZIKV infections effectively.

Biallelic TYR and TKFC variants in Egyptian patients with OCA1 and new expanded TKFC features

BACKGROUND

Oculocutaneous albinism type1 (OCA1) is caused by the TYR gene's homozygous and compound heterozygous variants. TKFC gene variants cause triokinase & FMN cyclase deficiency syndrome with variable multisystemic disorders.

OBJECTIVES

To determine the potential disease-causing variants in two deceased patients presenting atypical OCA1 features by demonstrating three generations for a single family. The two deceased neonates had severe skeletal abnormalities and fatal hypertrophic cardiomyopathy. We also explored the potential mechanisms for the causative relationship between TKFC and multisystem disorders.

PATIENTS AND METHODS

Due to the new emerging symptoms that weren't reported before with the TYR gene, the following methods were performed: Sanger sequencing for the TYR gene, followed by whole exome sequencing, co-segregation, and computational analyses.

RESULTS

Extensive parental consanguinity was found, and consequently an autosomal recessive mode of inheritance was prioritized. Upon performing sequencing and segregation data, the following has been confirmed: positive co-segregation of nonsense homozygous NM_000372.5:c.346C > T p.(Arg116*) variant in TYR gene and multisystem disease-missense homozygous NM_015533.4:c.598G > A p.(Val200Ile) variant in TKFC gene in the two affected index patients who deceased due to hypertrophic cardiomyopathy. Using computational analysis, we found that c.598G > A p.(Val200Ile) pathogenicity has led to the failure of L2-K1 active site closure due to the potential differential fluctuation between valine and isoleucine residues. Subsequently, disruption of endogenous DHA phosphorylation was found. Two potential mechanisms exploring the causative relationship between TKFC gene and multisystem disorders have been suggested.

CONCLUSIONS

This study presented a first family with the co-existence of biallelic variants in TYR and TKFC genes associating severe skeletal abnormalities and lethal hypertrophic cardiomyopathy. Neither of these genes would have been pursued in the standard genetic counseling. Such discovery is paving the way for more efficient genetic counseling. Comparing TKFC results with literature data showed that our relevant expanded TKFC variant is the 3rd worldwide.

Bibliometric analysis of publications on genetic polymorphism and external apical root resorption research

OBJECTIVE

This study aimed to analyze the scientific production of genetic polymorphisms and external apical root resorption (EARR) to establish main findings, geographic trends, and research gaps for possible future investigations.

METHODS

Unrestricted publications were searched using the Scopus database (March 2023) to include studies that addressed the association between genetic polymorphisms and EARR. Case-control, cohort, cross-sectional, and review studies were considered eligible. The softwares VOS viewer™ and Bibliometrix were used for data analysis.

RESULTS

Of the 44 studies analyzed, "Iglesias-Linares A" was the most cited author. The University of Seville (Spain) conducted the most research on this topic. Brazil, Spain, and the USA were the leading countries in terms of citations. The most frequent term in the co-occurrence of keywords was "EARR." The journal American Journal of Orthodontics and Dentofacial Orthopedics presented a great relevance in the area, demonstrating a high number of publications. Several genetic polymorphisms have been investigated, with interleukins being the most studied.

CONCLUSION

Endodontics is an area of research that should focus more on root resorption and genetic polymorphisms, as it still underexplored, compared to orthodontics. Polymorphisms have been studied as possible predictors of EARR caused by orthodontic tooth movement. However, the gap in the research indicates a need to search for new genes associated with EARR.

IFIH1 variants are associated with generalised epilepsy preceded by febrile seizures

BACKGROUND

IFIH1 variants have been reported to be associated with immune-related disorders with/without seizures. It is unknown whether IFIH1 variants are associated with common epilepsy without acquired causes and the mechanism underlying phenotypic variation remains elusive.

METHODS

Trio-based whole-exome sequencing was performed on patients with febrile seizures or epilepsy with antecedent febrile seizures. Previously reported variants were systematically reviewed to investigate genotype-phenotype associations.

RESULTS

Two de novo heterozygous and three biallelic missense variants were identified in five patients with generalised epilepsy with antecedent febrile seizures. The variants were predicted to be damaging by in silico tools and were associated with hydrogen bonding changes to neighbouring amino acids or decreased protein stability. Patients exhibited an early onset age and became seizure-free with favourable outcome. Further analysis revealed that de novo missense variants located in the Hel region resulted in seizures with multiple neurological abnormalities, while those in the pincer domain or C-terminal domain led to seizures with normal neurodevelopment, suggesting a sub-molecular effect. Biallelic missense variants, which were inherited from unaffected parents and presented low allele frequencies in general populations, were associated with seizures without neurological abnormalities. Truncation variants were related to refractory epilepsy and severe developmental delay, suggesting a genotype-phenotype correlation. IFIH1 is predominantly expressed in the neonatal stage and decreases dramatically in the adulthood, which is consistent with the early onset age and favourable outcome of the patients.

CONCLUSIONS

IFIH1 variants are potentially associated with generalised epilepsy with antecedent febrile seizures. The sub-molecular implication and genotype-phenotype association help explain phenotype variations of IFIH1 variants.

Unraveling the Mechanisms of Valvular Heart Disease to Identify Medical Therapy Targets: A Scientific Statement From the American Heart Association

Valvular heart disease is a common cause of morbidity and mortality worldwide and has no effective medical therapy. Severe disease is managed with valve replacement procedures, which entail high health care-related costs and postprocedural morbidity and mortality. Robust ongoing research programs have elucidated many important molecular pathways contributing to primary valvular heart disease. However, there remain several key challenges inherent in translating research on valvular heart disease to viable molecular targets that can progress through the clinical trials pathway and effectively prevent or modify the course of these common conditions. In this scientific statement, we review the basic cellular structures of the human heart valves and discuss how these structures change in primary valvular heart disease. We focus on the most common primary valvular heart diseases, including calcific aortic stenosis, bicuspid aortic valves, mitral valve prolapse, and rheumatic heart disease, and outline the fundamental molecular discoveries contributing to each. We further outline potential therapeutic molecular targets for primary valvular heart disease and discuss key knowledge gaps that might serve as future research priorities.

IFIH1 loss of function predisposes to inflammatory and SARS-CoV-2-related infectious diseases

The IFIH1 gene, encoding melanoma differentiation-associated protein 5 (MDA5), is an indispensable innate immune regulator involved in the early detection of viral infections. Previous studies described MDA5 dysregulation in weakened immunological responses, and increased susceptibility to microbial infections and autoimmune disorders. Monoallelic gain-of-function of the IFIH1 gene has been associated with multisystem disorders, namely Aicardi-Goutieres and Singleton-Merten syndromes, while biallelic loss causes immunodeficiency. In this study, nine patients suffering from recurrent infections, inflammatory diseases, severe COVID-19 or multisystem inflammatory syndrome in children (MIS-C) were identified with putative loss-of-function IFIH1 variants by whole-exome sequencing. All patients revealed signs of lymphopaenia and an increase in inflammatory markers, including CRP, amyloid A, ferritin and IL-6. One patient with a pathogenic homozygous variant c.2807+1G>A was the most severe case showing immunodeficiency and glomerulonephritis. The c.1641+1G>C variant was identified in the heterozygous state in patients suffering from periodic fever, COVID-19 or MIS-C, while the c.2016delA variant was identified in two patients with inflammatory bowel disease or MIS-C. There was a significant association between IFIH1 monoallelic loss of function and susceptibility to infections in males. Expression analysis showed that PBMCs of one patient with a c.2016delA variant had a significant decrease in ISG15, IFNA and IFNG transcript levels, compared to normal PBMCs, upon stimulation with Poly(I:C), suggesting that MDA5 receptor truncation disrupts the immune response. Our findings accentuate the implication of rare monogenic IFIH1 loss-of-function variants in altering the immune response, and severely predisposing patients to inflammatory and infectious diseases, including SARS-CoV-2-related disorders.

High throughput functional profiling of genes at intraocular pressure loci reveals distinct networks for glaucoma

INTRODUCTION

Primary open angle glaucoma (POAG) is a leading cause of blindness globally. Characterized by progressive retinal ganglion cell degeneration, the precise pathogenesis remains unknown. Genome-wide association studies (GWAS) have uncovered many genetic variants associated with elevated intraocular pressure (IOP), one of the key risk factors for POAG. We aimed to identify genetic and morphological variation that can be attributed to trabecular meshwork cell (TMC) dysfunction and raised IOP in POAG.

METHODS

62 genes across 55 loci were knocked-out in a primary human TMC line. Each knockout group, including five non-targeting control groups, underwent single-cell RNA-sequencing (scRNA-seq) for differentially-expressed gene (DEG) analysis. Multiplexed fluorescence coupled with CellProfiler image analysis allowed for single-cell morphological profiling.

RESULTS

Many gene knockouts invoked DEGs relating to matrix metalloproteinases and interferon-induced proteins. We have prioritized genes at four loci of interest to identify gene knockouts that may contribute to the pathogenesis of POAG, including ANGPTL2, LMX1B, CAV1, and KREMEN1. Three genetic networks of gene knockouts with similar transcriptomic profiles were identified, suggesting a synergistic function in trabecular meshwork cell physiology. TEK knockout caused significant upregulation of nuclear granularity on morphological analysis, while knockout of TRIOBP, TMCO1 and PLEKHA7 increased granularity and intensity of actin and the cell-membrane.

CONCLUSION

High-throughput analysis of cellular structure and function through multiplex fluorescent single-cell analysis and scRNA-seq assays enabled the direct study of genetic perturbations at the single-cell resolution. This work provides a framework for investigating the role of genes in the pathogenesis of glaucoma and heterogenous diseases with a strong genetic basis.

Contrasting functions of ATP hydrolysis by MDA5 and LGP2 in viral RNA sensing

Cytosolic long dsRNA, among the most potent proinflammatory signals, is recognized by melanoma differentiation-associated protein 5 (MDA5). MDA5 binds dsRNA cooperatively forming helical filaments. ATP hydrolysis by MDA5 fulfills a proofreading function by promoting dissociation of shorter endogenous dsRNs from MDA5 while allowing longer viral dsRNAs to remain bound leading to activation of interferon-β responses. Here, we show that adjacent MDA5 subunits in MDA5-dsRNA filaments hydrolyze ATP cooperatively, inducing cooperative filament disassembly. Consecutive rounds of ATP hydrolysis amplify the filament footprint, displacing tightly bound proteins from dsRNA. Our electron microscopy and biochemical assays show that LGP2 binds to dsRNA at internal binding sites through noncooperative ATP hydrolysis. Unlike MDA5, LGP2 has low nucleic acid selectivity and can hydrolyze GTP and CTP as well as ATP. Binding of LGP2 to dsRNA promotes nucleation of MDA5 filament assembly resulting in shorter filaments. Molecular modeling identifies an internally bound MDA5-LGP2-RNA complex, with the LGP2 C-terminal tail forming the key contacts with MDA5. These contacts are specifically required for NTP-dependent internal RNA binding. We conclude that NTPase-dependent binding of LGP2 to internal dsRNA sites complements NTPase-independent binding to dsRNA ends, via distinct binding modes, to increase the number and signaling output of MDA5-dsRNA complexes.

Innate immune responses to RNA: sensing and signaling

Nucleic acids are among the most essential PAMPs (pathogen-associated molecular patterns). Animals have evolved numerous sensors to recognize nucleic acids and trigger immune signaling against pathogen replication, cellular stress and cancer. Many sensor proteins (e.g., cGAS, AIM2, and TLR9) recognize the molecular signature of infection or stress and are responsible for the innate immune response to DNA. Remarkably, recent evidence demonstrates that cGAS-like receptors acquire the ability to sense RNA in some forms of life. Compared with the nucleic-acid sensing by cGAS, innate immune responses to RNA are based on various RNA sensors, including RIG-I, MDA5, ADAR1, TLR3/7/8, OAS1, PKR, NLRP1/6, and ZBP1, via a broad-spectrum signaling axis. Importantly, new advances have brought to light the potential clinical application of targeting these signaling pathways. Here, we highlight the latest discoveries in the field. We also summarize the activation and regulatory mechanisms of RNA-sensing signaling. In addition, we discuss how RNA sensing is tightly controlled in cells and why the disruption of immune homeostasis is linked to disease.

Superfamily II helicases: the potential therapeutic target for cardiovascular diseases

Cardiovascular diseases (CVDs) still maintain high morbidity and mortality globally. Helicases, a unique class of enzymes, are extensively implicated in the processes of nucleic acid (NA) metabolism across various organisms. They play a pivotal role in gene expression, inflammatory response, lipid metabolism, and so forth. However, abnormal helicase expression has been associated with immune response, cancer, and intellectual disability in humans. Superfamily II (SFII) is one of the largest and most diverse of the helicase superfamilies. Increasing evidence has implicated SFⅡ helicases in the pathogenesis of multiple CVDs. In this review, we comprehensively review the regulation mechanism of SFⅡ helicases in CVDs including atherosclerosis, myocardial infarction, cardiomyopathies, and heart failure, which will contribute to the investigation of ideal therapeutic targets for CVDs.

A zebrafish model of Ifih1-driven Aicardi-Goutières syndrome reproduces the interferon signature and the exacerbated inflammation of patients

Type I interferonopathies are a heterogenic group of rare diseases associated with an increase in type I interferon (IFN). The main challenge for the study of Type I interferonopathies is the lack of a well-founded animal model to better characterize the phenotype as well as to perform fast and large drug screenings to offer the best treatment options. In this study, we report the development of a transgenic zebrafish model of Type I interferonopathy overexpressing ifih1 carrying the mutation p.Arg742His (Tg(ifih1_mut)), corresponding to the human mutation p.Arg779His. RNA sequence analysis from Tg(ifih1_mut) larvae revealed a systemic inflammation and IFN signature upon a suboptimal poly I:C induction compared with wild-type larvae, confirming the phenotype observed in patients suffering from Type I interferonopathies. More interestingly, the phenotype was manifested in the zebrafish inflammation and Type I IFN reporters nfkb:eGFP and isg15:eGFP, respectively, making this zebrafish model suitable for future high-throughput chemical screening (HTS). Using the unique advantages of the zebrafish model for gene editing, we have generated Tg(ifih1_mut) knocked down for mavs and ikbke, which completely abrogated the Poly I:C induction and activation of the GFP of the reporters. Finally, we used an FDA-approved drug, Baricitinib (Jak1/Jak2 inhibitor), which was able to reduce the inflammation and the ISG expression. Our results demonstrate the potential of this model to further understand AGS pathological mechanisms and to identify novel therapeutic drugs by HTS.

Differential Gene Expression Profiles and Pathways Highlight the Role of Osteoimmunology in Neurofibromatosis Type 1-Related Dystrophic Scoliosis With Osteopenia

STUDY DESIGN

Microarray approach and integrated gene network analysis.

OBJECTIVE

To explore the differential genetic expression profile, Gene Ontology terms, and Kyoto Encyclopedia of Genes and Genomes pathways in human trabecular bone (HTB)-derived cells of dystrophic scoliosis secondary to neurofibromatosis type 1 (DS-NF1) and compare these to normal controls.

SUMMARY OF BACKGROUND DATA

The pathogenesis of DS-NF1 and the accompanying generalized osteopenia remain unclear. We hypothesized that HTBs may play a significant role in the etiology and pathogenesis of DS-NF1.

MATERIALS AND METHODS

Microarray analysis was used to identify differentially expressed genes of HTBs from patients with DS-NF1 compared with those from healthy individuals. Functional and pathway enrichment analysis were implemented through Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway database. Then, the "search tool for the retrieval of interacting genes/proteins" database, Cytoscape, and "Molecular Complex Detection" were applied to construct the protein-protein interaction (PPI) network and screen hub genes. Pathway enrichment analysis was further performed for hub genes and gene clusters identified through module analysis. Six potential crucial genes were selected for validation by reverse transcription polymerase chain reaction.

RESULTS

Bioinformatic analysis revealed that there are 401 previously unrecognized differentially expressed genes (238 up and 163 downregulated genes) in HTBs from patients with DS-NF1, and they were mainly enriched in terms of immune response, type-I interferon (IFN) signaling, TNF signaling pathway and etinoic acid inducible gene I-like receptor signaling pathway. Five hub genes, including signal transducer and activator of transcription 1, 2'-5'-oligoadenylate synthetase-like, IFN induced with helicase C domain 1, IFN regulatory factor 7, and MX dynamin-like GTPase 1 were identified through PPI network, which were mainly enriched in terms of Jak-STAT and etinoic acid inducible gene I-like receptor signaling pathway. An independently dysregulated protein cluster containing CCL2, CXCL1, CXCL3, CX3CL1, TLR1 , and CXCL12 was also identified through the PPI network. This indicated that the upper abnormally expressed genes may play essential roles in DS-NF1 pathogenesis and accompanied osteopenia.

CONCLUSION

Six key genes were identified in the progression of DS-NF1-related osteopenia. Immune response might play a key role in the progression of osteopenia, whereas a CXCL12 -mediated osteogenic effect might play a protective role.

Type I Interferonopathies: A Clinical Review

This review will discuss when clinicians should consider evaluating for Type I interferonopathies, review clinical phenotypes and molecular defects of Type I interferonopathies, and discuss current treatments.

Ruxolitinib altered IFN-β induced necroptosis of human dental pulp stem cells during osteoblast differentiation

OBJECTIVE

This study aimed to evaluate the role of ruxolitinib in the interferon beta (IFN-β) mediated osteoblast differentiation using human dental pulp stem cells (hDPSCs).

DESIGN

hDPSCs from five deciduous teeth of healthy patients were stimulated by adding human recombinant IFN-β protein (1 or 2 ng/ml) to the osteogenic differentiation induction medium. Substrate formation was determined using Alizarin Red staining, calcium concentration, and osteoblast marker expression levels. Ruxolitinib was used to inhibit the Janus kinase/signal transducers and activators of transcription (JAK-STAT) pathway. Apoptosis was detected using terminal deoxynucleotidyl nick-end labeling (TUNEL) staining, and necroptosis was detected using propidium iodide staining and phosphorylated mixed lineage kinase domain-like protein (pMLKL) expression.

RESULTS

In the IFN-β-treated group, substrate formation was inhibited by a reduction in alkaline phosphatase (ALP) expression in a concentration-dependent manner. Although the proliferation potency was unchanged between the IFN-β-treated and control groups, the cell number was significantly reduced in the experimental group. TUNEL-positive cell number was not significantly different; however, the protein level of necroptosis markers, interleukin-6 (IL-6) and pMLKL were significantly increased in the substrate formation. Cell number and ALP expression level were improved in the group administered ruxolitinib, a JAK-STAT inhibitor. Additionally, ruxolitinib significantly suppressed IL-6 and pMLKL levels.

CONCLUSION

Ruxolitinib interfered with the IFN-β-mediated necroptosis and osteogenic differentiation via the JAK-STAT pathway.

GWAS meta-analysis of psoriasis identifies new susceptibility alleles impacting disease mechanisms and therapeutic targets

Psoriasis is a common, debilitating immune-mediated skin disease. Genetic studies have identified biological mechanisms of psoriasis risk, including those targeted by effective therapies. However, the genetic liability to psoriasis is not fully explained by variation at robustly identified risk loci. To move towards a saturation map of psoriasis susceptibility we meta-analysed 18 GWAS comprising 36,466 cases and 458,078 controls and identified 109 distinct psoriasis susceptibility loci, including 45 that have not been previously reported. These include susceptibility variants at loci in which the therapeutic targets IL17RA and AHR are encoded, and deleterious coding variants supporting potential new drug targets (including in STAP2, CPVL and POU2F3). We conducted a transcriptome-wide association study to identify regulatory effects of psoriasis susceptibility variants and cross-referenced these against single cell expression profiles in psoriasis-affected skin, highlighting roles for the transcriptional regulation of haematopoietic cell development and epigenetic modulation of interferon signalling in psoriasis pathobiology.

Cellular functions of eukaryotic RNA helicases and their links to human diseases

RNA helicases are highly conserved proteins that use nucleoside triphosphates to bind or remodel RNA, RNA-protein complexes or both. RNA helicases are classified into the DEAD-box, DEAH/RHA, Ski2-like, Upf1-like and RIG-I families, and are the largest class of enzymes active in eukaryotic RNA metabolism - virtually all aspects of gene expression and its regulation involve RNA helicases. Mutation and dysregulation of these enzymes have been linked to a multitude of diseases, including cancer and neurological disorders. In this Review, we discuss the regulation and functional mechanisms of RNA helicases and their roles in eukaryotic RNA metabolism, including in transcription regulation, pre-mRNA splicing, ribosome assembly, translation and RNA decay. We highlight intriguing models that link helicase structure, mechanisms of function (such as local strand unwinding, translocation, winching, RNA clamping and displacing RNA-binding proteins) and biological roles, including emerging connections between RNA helicases and cellular condensates formed through liquid-liquid phase separation. We also discuss associations of RNA helicases with human diseases and recent efforts towards the design of small-molecule inhibitors of these pivotal regulators of eukaryotic gene expression.

A-to-I RNA editing by ADAR and its therapeutic applications: From viral infections to cancer immunotherapy

ADAR deaminases catalyze adenosine-to-inosine (A-to-I) editing on double-stranded RNA (dsRNA) substrates that regulate an umbrella of biological processes. One of the two catalytically active ADAR enzymes, ADAR1, plays a major role in innate immune responses by suppression of RNA sensing pathways which are orchestrated through the ADAR1-dsRNA-MDA5 axis. Unedited immunogenic dsRNA substrates are potent ligands for the cellular sensor MDA5. Upon activation, MDA5 leads to the induction of interferons and expression of hundreds of interferon-stimulated genes with potent antiviral activity. In this way, ADAR1 acts as a gatekeeper of the RNA sensing pathway by striking a fine balance between innate antiviral responses and prevention of autoimmunity. Reduced editing of immunogenic dsRNA by ADAR1 is strongly linked to the development of common autoimmune and inflammatory diseases. In viral infections, ADAR1 exhibits both antiviral and proviral effects. This is modulated by both editing-dependent and editing-independent functions, such as PKR antagonism. Several A-to-I RNA editing events have been identified in viruses, including in the insidious viral pathogen, SARS-CoV-2 which regulates viral fitness and infectivity, and could play a role in shaping viral evolution. Furthermore, ADAR1 is an attractive target for immuno-oncology therapy. Overexpression of ADAR1 and increased dsRNA editing have been observed in several human cancers. Silencing ADAR1, especially in cancers that are refractory to immune checkpoint inhibitors, is a promising therapeutic strategy for cancer immunotherapy in conjunction with epigenetic therapy. The mechanistic understanding of dsRNA editing by ADAR1 and dsRNA sensing by MDA5 and PKR holds great potential for therapeutic applications. This article is categorized under: RNA Processing > RNA Editing and Modification RNA in Disease and Development > RNA in Disease.

Asymmetric arginine dimethylation of cytosolic RNA and DNA sensors by PRMT3 attenuates antiviral innate immunity

The cytosolic RNA and DNA sensors initiate type I interferon signaling when binding to RNA or DNA. To effectively protect the host against virus infection and concomitantly avoid excessive interferonopathy at resting states, these sensors must be tightly regulated. However, the key molecular mechanisms regulating these sensors' activation remain elusive. Here, we identify PRMT3, a type I protein arginine methyltransferase, as a negative regulator of cytosolic RNA and DNA sensors. PRMT3 interacts with RIG-I, MDA5, and cGAS and catalyzes asymmetric dimethylation of R730 on RIG-I, R822 on MDA5, and R111 on cGAS. These modifications reduce RNA-binding ability of RIG-I and MDA5 as well as DNA-binding ability and oligomerization of cGAS, leading to the inhibition of downstream type I interferon production. Furthermore, mice with loss of one copy of Prmt3 or in vivo treatment of the PRMT3 inhibitor, SGC707, are more resistant to RNA and DNA virus infection. Our findings reveal an essential role of PRMT3 in the regulation of antiviral innate immunity and give insights into the molecular regulation of cytosolic RNA and DNA sensors' activation.

Hereditary dentin defects with systemic diseases

OBJECTIVE

This review aimed to summarize recent progress on syndromic dentin defects, promoting a better understanding of systemic diseases with dentin malformations, the molecules involved, and related mechanisms.

SUBJECTS AND METHODS

References on genetic diseases with dentin malformations were obtained from various sources, including PubMed, OMIM, NCBI, and other websites. The clinical phenotypes and genetic backgrounds of these diseases were then summarized, analyzed, and compared.

RESULTS

Over 10 systemic diseases, including osteogenesis imperfecta, hypophosphatemic rickets, vitamin D-dependent rickets, familial tumoral calcinosis, Ehlers-Danlos syndrome, Schimke immuno-osseous dysplasia, hypophosphatasia, Elsahy-Waters syndrome, Singleton-Merten syndrome, odontochondrodysplasia, and microcephalic osteodysplastic primordial dwarfism type II were examined. Most of these are bone disorders, and their pathogenic genes may regulate both dentin and bone development, involving extracellular matrix, cell differentiation, and metabolism of calcium, phosphorus, and vitamin D. The phenotypes of these syndromic dentin defects various with the involved genes, part of them are similar to dentinogenesis imperfecta or dentin dysplasia, while others only present one or two types of dentin abnormalities such as discoloration, irregular enlarged or obliterated pulp and canal, or root malformation.

CONCLUSION

Some specific dentin defects associated with systemic diseases may serve as important phenotypes for dentists to diagnose. Furthermore, mechanistic studies on syndromic dentin defects may provide valuable insights into isolated dentin defects and general dentin development or mineralization.

Genetics of SLE: mechanistic insights from monogenic disease and disease-associated variants

The past few years have provided important insights into the genetic architecture of systemic autoimmunity through aggregation of findings from genome-wide association studies (GWAS) and whole-exome or whole-genome sequencing studies. In the prototypic systemic autoimmune disease systemic lupus erythematosus (SLE), monogenic disease accounts for a small fraction of cases but has been instrumental in the elucidation of disease mechanisms. Defects in the clearance or digestion of extracellular or intracellular DNA or RNA lead to increased sensing of nucleic acids, which can break B cell tolerance and induce the production of type I interferons leading to tissue damage. Current data suggest that multiple GWAS SLE risk alleles act in concert with rare functional variants to promote SLE development. Moreover, introduction of orthologous variant alleles into mice has revealed that pathogenic X-linked dominant and recessive SLE can be caused by novel variants in TLR7 and SAT1, respectively. Such bespoke models of disease help to unravel pathogenic pathways and can be used to test targeted therapies. Cell type-specific expression data revealed that most GWAS SLE risk genes are highly expressed in age-associated B cells (ABCs), which supports the view that ABCs produce lupus autoantibodies and contribute to end-organ damage by persisting in inflamed tissues, including the kidneys. ABCs have thus emerged as key targets of promising precision therapeutics.

JAK Inhibition in Juvenile Idiopathic Arthritis (JIA): Better Understanding of a Promising Therapy for Refractory Cases

Juvenile idiopathic arthritis (JIA) is a heterogeneous group of diseases with probably differential underlying physiopathology. Despite the revolutionary era of biologics, some patients remain difficult to treat because of disease severity, drug adverse events, drug allergy or association with severe comorbidities, i.e., uveitis, interstitial lung disease and macrophagic activation syndrome. Janus Kinase (JAK) inhibitors are small molecules that target JAK/Signal Transducers and Activators of Transcription (STAT) pathways, which could then prevent the activity of several proinflammatory cytokines. They may provide a useful alternative in these cases of JIA or in patients actually affected by Mendelian disorders mimicking JIA, such as type I interferonopathies with joint involvement, and might be the bridge for haematopoietic stem cell transplantation in these disabling conditions. As these treatments may have side effects that should not be ignored, ongoing and further controlled studies are still needed to provide data underlying long-term safety considerations in children and delineate subsets of JIA patients that will benefit from these promising treatments.

Activation of cytosolic RNA sensors by endogenous ligands: roles in disease pathogenesis

Early detection of infection is a central and critical component of our innate immune system. Mammalian cells have developed specialized receptors that detect RNA with unusual structures or of foreign origin - a hallmark of many virus infections. Activation of these receptors induces inflammatory responses and an antiviral state. However, it is increasingly appreciated that these RNA sensors can also be activated in the absence of infection, and that this 'self-activation' can be pathogenic and promote disease. Here, we review recent discoveries in sterile activation of the cytosolic innate immune receptors that bind RNA. We focus on new aspects of endogenous ligand recognition uncovered in these studies, and their roles in disease pathogenesis.

Toll-Like Receptor 3 Mediates Aortic Stenosis Through a Conserved Mechanism of Calcification

BACKGROUND

Calcific aortic valve disease (CAVD) is characterized by a phenotypic switch of valvular interstitial cells to bone-forming cells. Toll-like receptors (TLRs) are evolutionarily conserved pattern recognition receptors at the interface between innate immunity and tissue repair. Type I interferons (IFNs) are not only crucial for an adequate antiviral response but also implicated in bone formation. We hypothesized that the accumulation of endogenous TLR3 ligands in the valvular leaflets may promote the generation of osteoblast-like cells through enhanced type I IFN signaling.

METHODS

Human valvular interstitial cells isolated from aortic valves were challenged with mechanical strain or synthetic TLR3 agonists and analyzed for bone formation, gene expression profiles, and IFN signaling pathways. Different inhibitors were used to delineate the engaged signaling pathways. Moreover, we screened a variety of potential lipids and proteoglycans known to accumulate in CAVD lesions as potential TLR3 ligands. Ligand-receptor interactions were characterized by in silico modeling and verified through immunoprecipitation experiments. Biglycan (Bgn), Tlr3, and IFN-α/β receptor alpha chain (Ifnar1)-deficient mice and a specific zebrafish model were used to study the implication of the biglycan (BGN)-TLR3-IFN axis in both CAVD and bone formation in vivo. Two large-scale cohorts (GERA [Genetic Epidemiology Research on Adult Health and Aging], n=55 192 with 3469 aortic stenosis cases; UK Biobank, n=257 231 with 2213 aortic stenosis cases) were examined for genetic variation at genes implicated in BGN-TLR3-IFN signaling associating with CAVD in humans.

RESULTS

Here, we identify TLR3 as a central molecular regulator of calcification in valvular interstitial cells and unravel BGN as a new endogenous agonist of TLR3. Posttranslational BGN maturation by xylosyltransferase 1 (XYLT1) is required for TLR3 activation. Moreover, BGN induces the transdifferentiation of valvular interstitial cells into bone-forming osteoblasts through the TLR3-dependent induction of type I IFNs. It is intriguing that Bgn-/-, Tlr3-/-, and Ifnar1-/- mice are protected against CAVD and display impaired bone formation. Meta-analysis of 2 large-scale cohorts with >300 000 individuals reveals that genetic variation at loci relevant to the XYLT1-BGN-TLR3-interferon-α/β receptor alpha chain (IFNAR) 1 pathway is associated with CAVD in humans.

CONCLUSIONS

This study identifies the BGN-TLR3-IFNAR1 axis as an evolutionarily conserved pathway governing calcification of the aortic valve and reveals a potential therapeutic target to prevent CAVD.

Interferon and autoantigens: intersection in autoimmunity

Interferon (IFN) is a key component of the innate immune response. For reasons that remain incompletely understood, the IFN system is upregulated in several rheumatic diseases, particularly those that feature autoantibody production, such as SLE, Sjögren's syndrome, myositis and systemic sclerosis. Interestingly, many of the autoantigens targeted in these diseases are components of the IFN system, representing IFN-stimulated genes (ISGs), pattern recognition receptors (PRRs), and modulators of the IFN response. In this review, we describe features of these IFN-linked proteins that may underlie their status as autoantigens. Note is also made of anti-IFN autoantibodies that have been described in immunodeficiency states.

Type I Interferonopathies in Childhood

Type 1 interferonopathy is a novel context reflecting a group of inborn disorders sharing common pathway disturbances. This group of diseases is characterized by autoimmunity and autoinflammation caused by an upregulation of type 1 interferons (IFN)s due to certain genetic mutations. Several features are common in most of the diseases in this group, such as vasculitic skin changes, including chilblains, panniculitis, interstitial lung disease, basal ganglion calcifications, neuromotor impairments, epilepsy, stroke, and recurrent fever. Family history and consanguineous marriage are also common. IFN signature is a useful diagnostic tool and is positive in almost all patients with type 1 interferonopathies. Although IFN signature is a sensitive test, its specificity is relatively low. It can also be positive in viral infections and several connective tissue diseases. Therefore, next-generation sequence methods, whole exome sequencing (WES) in particular, are required for the ultimate diagnosis. The optimal treatment regime is still under debate due to a lack of clinical trials. Although high-dose steroids, anti-IL-1 and anti-IL-6 treatments, and reverse transcriptase inhibitors are used, JAK inhibitors are highly promising. Additionally, monoclonal antibodies against IFN-alpha and interferon-α receptor (IFNAR) are currently underway.

Clinical Implications of a New DDX58 Pathogenic Variant That Causes Lupus Nephritis due to RIG-I Hyperactivation

BACKGROUND

Lupus nephritis (LN) is one of the most severe complications of systemic lupus erythematosus, with heterogeneous phenotypes and different responses to therapy. Identifying genetic causes of LN can facilitate more individual treatment strategies.

METHODS

We performed whole-exome sequencing in a cohort of Chinese patients with LN and identified variants of a disease-causing gene. Extensive biochemical, immunologic, and functional analyses assessed the effect of the variant on type I IFN signaling. We further investigated the effectiveness of targeted therapy using single-cell RNA sequencing.

RESULTS

We identified a novel DDX58 pathogenic variant, R109C, in five unrelated families with LN. The DDX58 R109C variant is a gain-of-function mutation, elevating type I IFN signaling due to reduced autoinhibition, which leads to RIG-I hyperactivation, increased RIG-I K63 ubiquitination, and MAVS aggregation. Transcriptome analysis revealed an increased IFN signature in patient monocytes. Initiation of JAK inhibitor therapy (baricitinib 2 mg/d) effectively suppressed the IFN signal in one patient.

CONCLUSIONS

A novel DDX58 R109C variant that can cause LN connects IFNopathy and LN, suggesting targeted therapy on the basis of pathogenicity.

PODCAST

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Case report: Pneumocystis jirovecii pneumonia in a severe case of Aicardi-Goutières syndrome with an IFIH1 gain-of-function mutation mimicking combined immunodeficiency

Aicardi-Goutières syndrome (AGS) is a genetically determined early-onset progressive encephalopathy caused by mutations leading to overexpression of type I interferon (IFN) and resulting in various clinical phenotypes. A gain-of-function (GOF) mutation in the IFIH1 gene is associated with robust production of type I IFN and activation of the Janus kinase (JAK) signal transducer and activator of the transcription (STAT) pathway, which can cause AGS type 7. We detail the clinical case of an infant who initially presented with Pneumocystis jirovecii pneumonia (PCP), had recurrent respiratory infections, and was later treated with a JAK inhibitor, baricitinib, because of a genetically confirmed GOF mutation in the IFIH1 gene. This spectrum of IFIH1 GOF mutations with overlapping features of hyperinflammation and severe opportunistic infection, which mimics combined immunodeficiency (CID), has not been described before. In this case, therapy with baricitinib effectively blocked IFN-α activation and reduced STAT1 signaling but had no effect on the progression of the neurological disease.

Molecular Mechanisms of Vascular Health: Insights From Vascular Aging and Calcification

Cardiovascular disease is the most common cause of death worldwide, especially beyond the age of 65 years, with the vast majority of morbidity and mortality due to myocardial infarction and stroke. Vascular pathology stems from a combination of genetic risk, environmental factors, and the biologic changes associated with aging. The pathogenesis underlying the development of vascular aging, and vascular calcification with aging, in particular, is still not fully understood. Accumulating data suggests that genetic risk, likely compounded by epigenetic modifications, environmental factors, including diabetes and chronic kidney disease, and the plasticity of vascular smooth muscle cells to acquire an osteogenic phenotype are major determinants of age-associated vascular calcification. Understanding the molecular mechanisms underlying genetic and modifiable risk factors in regulating age-associated vascular pathology may inspire strategies to promote healthy vascular aging. This article summarizes current knowledge of concepts and mechanisms of age-associated vascular disease, with an emphasis on vascular calcification.

Altered RNA Editing in Atopic Dermatitis Highlights the Role of Double-Stranded RNA for Immune Surveillance

Atopic dermatitis (AD) is associated with dysregulated type 1 IFN‒mediated responses, in parallel with the dominant type 2 inflammation. However, the pathophysiology of this dysregulation is largely unknown. Adenosine-to-inosine RNA editing plays a critical role in immune regulation by preventing double-stranded RNA recognition by MDA5 and IFN activation. We studied global adenosine-to-inosine editing in AD to elucidate the role played by altered editing in the pathophysiology of this disease. Analysis of three RNA-sequencing datasets of AD skin samples revealed reduced levels of adenosine-to-inosine RNA editing in AD. This reduction was seen globally throughout Alu repeats as well as in coding genes and in specific pre-mRNA loci expected to create long double-stranded RNA, the main substrate of MDA5 leading to type I IFN activation. Consistently, IFN signature genes were upregulated. In contrast, global editing was not altered in systemic lupus erythematosus and systemic sclerosis, despite IFN activation. Our results indicate that altered editing leading to impairment of the innate immune response may be involved in the pathogenesis of AD. Possibly, it may be relevant for additional autoimmune and inflammatory diseases.

Double-Stranded RNA Induces Mortality in an MDA5-Mediated Type I Interferonopathy Model

Gain-of-function mutations in the viral dsRNA sensor melanoma differentiation-associated protein 5 (MDA5) lead to autoimmune IFNopathies, including Singleton-Merten syndrome (SMS) and Aicardi-Goutières syndrome. However, much remains unclear regarding the mechanism of disease progression and how external factors such as infection or immune stimulation with vaccination can affect the immune response. With this aim, we generated mice with human MDA5 bearing the SMS-associated mutation R822Q (hM-R822Q). hM-R822Q transgenic (Tg) mice developed SMS-like heart fibrosis, aortic valve enlargement, and aortic calcification with a systemic IFN-stimulated gene signature resulting in the activation of the adaptive immune response. Although administration of the viral dsRNA mimic polyinosinic-polycytidylic acid [poly(I:C)] did not have remarkable effects on the cardiac phenotype, dramatic inflammation was observed in the intestines where IFN production was most elevated. Poly(I:C)-injected hM-R822Q Tg mice also developed lethal hypercytokinemia marked by massive IL-6 levels in the serum. Interrupting the IFN signaling through mitochondrial antiviral signaling protein or IFN-α/β receptor alleviated hM-R822Q-induced inflammation. Furthermore, inhibition of JAK signaling with tofacitinib reduced cytokine production and ameliorated mucosal damage, enabling the survival of poly(I:C)-injected hM-R822Q Tg mice. These findings demonstrate that the MDA5 R822Q mutant introduces a critical risk factor for uncontrollable inflammation on viral infection or vaccination.

Shared genetic risk factors and causal association between psoriasis and coronary artery disease

Psoriasis and coronary artery disease (CAD) are related comorbidities that are well established, but whether a genetic basis underlies this is not well studied. We apply trans-disease meta-analysis to 11,024 psoriasis and 60,801 CAD cases, along with their associated controls, identifying one opposing and three shared genetic loci, which are confirmed through colocalization analysis. Combining results from Bayesian credible interval analysis with independent information from genomic, epigenomic, and spatial chromatin organization, we prioritize genes (including IFIH1 and IL23A) that have implications for common molecular mechanisms involved in psoriasis and CAD inflammatory signaling. Chronic systemic inflammation has been associated with CAD and myocardial infarction, and Mendelian randomization analysis finds that CAD as an exposure can have a significant causal effect on psoriasis (OR = 1.11; p = 3×10^-6) following adjustment for BMI and waist-hip ratio. Together, these findings suggest that systemic inflammation which causes CAD can increase the risk of psoriasis.

Emerging roles of the RNA modifications N6-methyladenosine and adenosine-to-inosine in cardiovascular diseases

Cardiovascular diseases lead the mortality and morbidity disease metrics worldwide. A multitude of chemical base modifications in ribonucleic acids (RNAs) have been linked with key events of cardiovascular diseases and metabolic disorders. Named either RNA epigenetics or epitranscriptomics, the post-transcriptional RNA modifications, their regulatory pathways, components, and downstream effects substantially contribute to the ways our genetic code is interpreted. Here we review the accumulated discoveries to date regarding the roles of the two most common epitranscriptomic modifications, N6-methyl-adenosine (m6A) and adenosine-to-inosine (A-to-I) editing, in cardiovascular disease.

Friend or foe: RIG- I like receptors and diseases

Retinoic acid-inducible gene I (RIG-I)-like receptors (RLRs), which are pivotal sensors of RNA virus invasions, mediate the transcriptional induction of genes encoding type I interferons (IFNs) and proinflammatory cytokines, successfully establishing host antiviral immune response. A few excellent reviews have elaborated on the structural biology of RLRs and the antiviral mechanisms of RLR activation. In this review, we give a basic understanding of RLR biology and summarize recent findings of how RLR signaling cascade is strictly controlled by host regulatory mechanisms, which include RLR-interacting proteins, post-translational modifications and microRNAs (miRNAs). Furthermore, we pay particular attention to the relationship between RLRs and diseases, especially how RLRs participate in SARS-CoV-2, malaria or bacterial infections, how single-nucleotide polymorphisms (SNPs) or mutations in RLRs and antibodies against RLRs lead to autoinflammatory diseases and autoimmune diseases, and how RLRs are involved in anti-tumor immunity. These findings will provide insights and guidance for antiviral and immunomodulatory therapies targeting RLRs.

Endogenous Retroviruses (ERVs): Does RLR (RIG-I-Like Receptors)-MAVS Pathway Directly Control Senescence and Aging as a Consequence of ERV De-Repression?

Bi-directional transcription of Human Endogenous Retroviruses (hERVs) is a common feature of autoimmunity, neurodegeneration and cancer. Higher rates of cancer incidence, neurodegeneration and autoimmunity but a lower prevalence of autoimmune diseases characterize elderly people. Although the re-expression of hERVs is commonly observed in different cellular models of senescence as a result of the loss of their epigenetic transcriptional silencing, the hERVs modulation during aging is more complex, with a peak of activation in the sixties and a decline in the nineties. What is clearly accepted, instead, is the impact of the re-activation of dormant hERV on the maintenance of stemness and tissue self-renewing properties. An innate cellular immunity system, based on the RLR-MAVS circuit, controls the degradation of dsRNAs arising from the transcription of hERV elements, similarly to what happens for the accumulation of cytoplasmic DNA leading to the activation of cGAS/STING pathway. While agonists and inhibitors of the cGAS-STING pathway are considered promising immunomodulatory molecules, the effect of the RLR-MAVS pathway on innate immunity is still largely based on correlations and not on causality. Here we review the most recent evidence regarding the activation of MDA5-RIG1-MAVS pathway as a result of hERV de-repression during aging, immunosenescence, cancer and autoimmunity. We will also deal with the epigenetic mechanisms controlling hERV repression and with the strategies that can be adopted to modulate hERV expression in a therapeutic perspective. Finally, we will discuss if the RLR-MAVS signalling pathway actively modulates physiological and pathological conditions or if it is passively activated by them.

Oral Phenotype of Singleton-Merten Syndrome: A Systematic Review Illustrated With a Case Report

Background: Singleton-Merten syndrome type 1 (SGMRT1) is a rare autosomal dominant disorder caused by IFIH1 variations with blood vessel calcifications, teeth anomalies, and bone defects. Aim: We aimed to summarize the oral findings in SGMRT1 through a systematic review of the literature and to describe the phenotype of a 10-year-old patient with SGMRT1 diagnosis. Results: A total of 20 patients were described in the literature, in nine articles. Eight IFIH1 mutations were described in 11 families. Delayed eruption, short roots, and premature loss of permanent teeth were the most described features (100%). Impacted teeth (89%) and carious lesions (67%) were also described. Our patient, a 10-year-old male with Singleton-Merten syndrome, presented numerous carious lesions, severe teeth malposition, especially in the anterior arch, and an oral hygiene deficiency with a 100% plaque index. The panoramic X-ray did not show any dental agenesis but revealed very short roots and a decrease in the jaw alveolar bone height. The whole-genome sequencing analysis revealed a heterozygous de novo variant in IFIH1 (NM_022168.4) c.2465G > A (p.Arg822Gln). Conclusion: Confused descriptions of oral features occurred in the literature between congenital findings and "acquired" pathology, especially carious lesions. The dental phenotype of these patients encompasses eruption anomalies (delayed eruption and impacted teeth) and lack of root edification, leading to premature loss of permanent teeth, and it may contribute to the diagnosis. An early diagnosis is essential to prevent teeth loss and to improve the quality of life of these patients. Systematic Review Registration: [https://www.crd.york.ac.uk/prospero/], identifier [CRD42022300025].