Moyamoya disease-associated protein mysterin/RNF213 is a novel AAA+ ATPase, which dynamically changes its oligomeric state

The emerging roles of non-canonical ubiquitination in proteostasis and beyond

Ubiquitin regulates various cellular functions by posttranslationally modifying substrates with diverse ubiquitin codes. Recent discoveries of new ubiquitin chain topologies, types of bonds, and non-protein substrates have substantially expanded the complexity of the ubiquitin code. Here, we describe the ubiquitin system covering the basic principles and recent discoveries related to mechanisms, technologies, and biological importance.

Molecular structure and function of mysterin/RNF213

Mysterin is a large intracellular protein harboring a RING finger ubiquitin ligase domain and is also referred to as RING finger protein 213 (RNF213). The author performed the first molecular cloning of the mysterin gene as the final step in genetic exploration of cerebrovascular moyamoya disease (MMD) and initiated the next round of exploration to understand its molecular and cellular functions. Although much remains unknown, accumulating findings suggest that mysterin functions in cells by targeting massive intracellular structures, such as lipid droplets (LDs) and various invasive pathogens. In the latter case, mysterin appears to directly surround and ubiquitylate the surface of pathogens and stimulate cell-autonomous antimicrobial reactions, such as xenophagy and inflammatory response. To date, multiple mutations causing MMD have been identified within and near the RING finger domain of mysterin; however, their functional relevance remains largely unknown. Besides the RING finger, mysterin harbors a dynein-like ATPase core and an RZ finger, another ubiquitin ligase domain unique to mysterin, while functional exploration of these domains has also just commenced. In this review, the author attempts to summarize the core findings regarding the molecular structure and function of the mysterin protein, with an emphasis on the perspective of MMD research.

De novo variants in RNF213 are associated with a clinical spectrum ranging from Leigh syndrome to early-onset stroke

PURPOSE

RNF213, encoding a giant E3 ubiquitin ligase, has been recognized for its role as a key susceptibility gene for moyamoya disease. Case reports have also implicated specific variants in RNF213 with an early-onset form of moyamoya disease with full penetrance. We aimed to expand the phenotypic spectrum of monogenic RNF213-related disease and to evaluate genotype-phenotype correlations.

METHODS

Patients were identified through reanalysis of exome sequencing data of an unselected cohort of unsolved pediatric cases and through GeneMatcher or ClinVar. Functional characterization was done by proteomics analysis and oxidative phosphorylation enzyme activities using patient-derived fibroblasts.

RESULTS

We identified 14 individuals from 13 unrelated families with (de novo) missense variants in RNF213 clustering within or around the Really Interesting New Gene (RING) domain. Individuals presented either with early-onset stroke (n = 11) or with Leigh syndrome (n = 3). No genotype-phenotype correlation could be established. Proteomics using patient-derived fibroblasts revealed no significant differences between clinical subgroups. 3D modeling revealed a clustering of missense variants in the tertiary structure of RNF213 potentially affecting zinc-binding suggesting a gain-of-function or dominant negative effect.

CONCLUSION

De novo missense variants in RNF213 clustering in the E3 RING or other regions affecting zinc-binding lead to an early-onset syndrome characterized by stroke or Leigh syndrome.

RNF213 in moyamoya disease: Genotype-phenotype association and the underlying mechanism

ABSTRACT

Moyamoya disease (MMD) is a cerebrovascular disorder characterized by a steno-occlusive internal carotid artery and compensatory vascular network formation. Although the precise pathogenic mechanism remains elusive, genetic association studies have identified RNF213 as the principal susceptibility gene for MMD, with the single nucleotide polymorphism p.R4810K recognized as the founder variant predominantly in the Asian populations. Distinct genotype-phenotype correlations are observable in RNF213-related MMD. The clinical manifestations linked to p.R4810K bear commonalities within Asian cohort, including familial predisposition, earlier age of onset, ischemic episodes, and involvement of the posterior cerebral artery (PCA). However, despite these shared phenotypic characteristics, there is significant heterogeneity in RNF213-related MMD presentations. This diversity manifests as variations across ethnic groups, inconsistent clinical symptoms and prognosis, and occurrence of other vasculopathies involving RNF213. This heterogeneity, in conjunction with the observed low disease penetrance of RNF213 mutations, suggests that the presence of these mutations may not be sufficient to cause MMD, underscoring the potential influence of other genetic or environmental factors. Although the current research might not have fully identified these additional contributors, experimental evidence points toward the involvement of RNF213 in angiogenesis, lipid metabolism, and the immune response. Future research is required to unveil the molecular mechanisms and identify the factors that synergize with RNF213 in the pathogenesis of MMD.

Comparative Serum Proteome Profiling of Canine Benign Prostatic Hyperplasia before and after Castration

BPH is the most prevalent prostatic condition in aging dogs. Nevertheless, clinical diagnosis and management remain inconsistent. This study employed in-solution digestion coupled with nano-liquid chromatography tandem mass spectrometry to assess serum proteome profiling of dogs with BPH and those dogs after castration. Male dogs were divided into two groups; control and BPH groups. In the BPH group, each dog was evaluated at two time points: Day 0 (BF subgroup) and Day 30 after castration (AT subgroup). In the BF subgroup, three proteins were significantly upregulated and associated with dihydrotestosterone: solute carrier family 5 member 5, tyrosine-protein kinase, and FRAT regulator of WNT signaling pathway 1. Additionally, the overexpression of polymeric immunoglobulin receptors in the BF subgroup hints at its potential as a novel protein linked to the BPH development process. Conversely, alpha-1-B glycoprotein (A1BG) displayed significant downregulation in the BF subgroup, suggesting A1BG's potential as a predictive protein for canine BPH. Finasteride was associated with increased proteins in the AT subgroup, including apolipoprotein C-I, apolipoprotein E, apolipoprotein A-II, TAO kinase 1, DnaJ homolog subfamily C member 16, PH domain and leucine-rich repeat protein phosphatase 1, neuregulin 1, and pseudopodium enriched atypical kinase 1. In conclusion, this pilot study highlighted alterations in various serum proteins in canine BPH, reflecting different pathological changes occurring in this condition. These proteins could be a source of potential non-invasive biomarkers for diagnosing this disease.

Identification of a Novel Hypoxia-induced Inflammatory Cell Death Pathway

Hypoxic cancer cells resist many anti-neoplastic therapies and can seed recurrence. We found previously that PTP1B deficiency promotes HER2+ breast cancer cell death in hypoxia by activating RNF213, an ∼600kDa protein containing AAA-ATPase domains and two ubiquitin ligase domains (RING and RZ) that also is implicated in Moyamoya disease (MMD), lipotoxicity, and innate immunity. Here we report that PTP1B and ABL1/2 reciprocally control RNF213 phosphorylation on tyrosine-1275. This phosphorylation promotes RNF213 oligomerization and RZ domain activation. The RZ domain ubiquitylates CYLD/SPATA2, and together with the LUBAC complex, induces their degradation. Decreased CYLD/SPATA2 causes NF-κB activation, which together with hypoxia-induced ER-stress triggers GDSMD-dependent pyroptosis. Mutagenesis experiments show that the RING domain negatively regulates the RZ domain. CYLD -deleted HER2+ cell-derived xenografts phenocopy the effects of PTP1B deficiency, and reconstituting RNF213 knockout lines with RNF213 mutants shows that the RZ domain mediates PTP1B-dependent tumor cell death. Our results identify a novel, potentially targetable PTP1B/RNF213/CYCLD/SPATA pathway critical for controlling inflammatory cell death in hypoxic tumors that could be exploited to target hypoxic tumor cells, potentially turning "cold" tumors "hot". Our findings also reveal new insights into RNF213 regulation, and have potentially important implications for the pathogenesis of MMD, atherosclerosis, and inflammatory and auto-immune disorders.

Autophagy and mitophagy-related extracellular mitochondrial dysfunction of cerebrospinal fluid cells in patients with hemorrhagic moyamoya disease

We aimed to investigate whether mitochondrial dysfunction in extracellular cerebrospinal fluid (CSF), which is associated with autophagy and mitophagy, might be involved in neurological outcomes in adult patients with hemorrhagic moyamoya disease (MMD) whose pathogenesis related to poor outcomes is not well-known. CSF samples were collected from 43 adult MMD patients and analyzed according to outcomes at 3 months. Fluorescence-activated cell sorter analysis (FACS) and the JC-1 red/green ratio were used to assess mitochondrial cells and intact mitochondrial membrane potential (MMP). We performed quantitative real-time polymerase chain reaction and Western blotting analyses of autophagy and mitophagy-related markers, including HIF1α, ATG5, pBECN1, BECN1, BAX, BNIP3L, DAPK1, and PINK1. Finally, FACS analysis with specific fluorescence-conjugated antibodies was performed to evaluate the potential cellular origin of CSF mitochondrial cells. Twenty-seven females (62.8%) with a mean age of 47.4 ± 9.7 years were included in the study. Among 43 patients with hemorrhagic MMD, 23 (53.5%) had poor outcomes. The difference in MMP was evident between the two groups (2.4 ± 0.2 in patients with poor outcome vs. 3.5 ± 0.4 in patients with good outcome; p = 0.02). A significantly higher expression (2-ΔCt) of HIF1α, ATG5, DAPK1 followed by BAX and BNIP3L mRNA and protein was also observed in poor-outcome patients compared to those with good outcomes. Higher percentage of vWF-positive mitochondria, suggesting endothelial cell origins, was observed in patients with good outcome compared with those with poor outcome (25.0 ± 1.4% in patients with good outcome vs. 17.5 ± 1.5% in those with poor outcome; p < 0.01). We observed the association between increased mitochondrial dysfunction concomitant with autophagy and mitophagy in CSF cells and neurological outcomes in adult patients with hemorrhagic MMD. Further prospective multicenter studies are needed to determine whether it has a diagnostic value for risk prediction.

The emerging role of E3 ubiquitin ligase RNF213 as an antimicrobial host determinant

Ring finger protein 213 (RNF213) is a large E3 ubiquitin ligase with a molecular weight of 591 kDa that is associated with moyamoya disease, a rare cerebrovascular disease. It is located in the cytosol and perinuclear space. Missense mutations in this gene have been found to be more prevalent in patients with moyamoya disease compared with that in healthy individuals. Understanding the molecular function of RNF213 could provide insights into moyamoya disease. RNF213 contains a C3HC4-type RING finger domain with an E3 ubiquitin ligase domain and six AAA+ adenosine triphosphatase (ATPase) domains. It is the only known protein with both AAA+ ATPase and ubiquitin ligase activities. Recent studies have highlighted the role of RNF213 in fighting against microbial infections, including viruses, parasites, bacteria, and chlamydiae. This review aims to summarize the recent research progress on the mechanisms of RNF213 in pathogenic infections, which will aid researchers in understanding the antimicrobial role of RNF213.

Amplified Risk of Intracranial Artery Stenosis/Occlusion Associated With RNF213 p.R4810K in Familial Hypercholesterolemia

Background

The RNF213 p.R4810K variant is associated with moyamoya disease in East Asian individuals and increases the risk of developing intracranial major artery stenosis/occlusion (ICASO) that affects anterior circulation. Meanwhile, 0.5% to 2.5% of asymptomatic East Asian individuals also carry this variant. As such, additional factors are likely required to develop ICASO in variant carriers. Familial hypercholesterolemia (FH) is a common genetic disorder in Japan that has a significant associated risk of developing premature coronary atherosclerosis; however, the relationship between ICASO and FH remains unknown.

Objectives

This study aimed to determine if FH facilitates RNF213 p.R4810K carriers to develop ICASO.

Methods

We enrolled patients with FH who had undergone brain magnetic resonance angiography at our hospital from May 2005 to March 2020. The RNF213 p.R4810K variant, and LDLR and PCSK9 mutations were genotyped. ICASO lesions in the brain magnetic resonance angiogram were analyzed.

Results

Six RNF213 p.R4810K variant carriers were identified among 167 patients with FH (LDLR, n = 104; PCSK9, n = 22). Five of the carriers (83.3%) exhibited ICASO in the anterior circulation; a significant difference in ICASO frequency was observed between the variant carriers and noncarriers (P = 0.025). The median number of stenotic or occluded arteries in the anterior circulation was also significantly larger in the variant carriers (3 vs 1, P = 0.01); however, did not differ between patients with FH with LDLR and PCSK9 mutations.

Conclusions

Patients with FH exhibit increased prevalence and severity of ICASO associated with RNF213 p.R4810K. Gene mutations for FH may confer an increased risk of ICASO in RNF213 p.R4810K carriers.

RNF213 Loss-of-Function Promotes Angiogenesis of Cerebral Microvascular Endothelial Cells in a Cellular State Dependent Manner

Enhanced and aberrant angiogenesis is one of the main features of Moyamoya disease (MMD) pathogenesis. The ring finger protein 213 (RNF213) and the variant p.R4810K have been linked with higher risks of MMD and intracranial arterial occlusion development in east Asian populations. The role of RNF213 in diverse aspects of the angiogenic process, such as proliferation, migration and capillary-like formation, is well-known but has been difficult to model in vitro. To evaluate the effect of the RNF213 MMD-associated gene on the angiogenic activity, we have generated RNF213 knockout in human cerebral microvascular endothelial cells (hCMEC/D3-RNF213^-/-) using the CRISPR-Cas9 system. Matrigel-based assay and a tri-dimensional (3D) vascularized model using the self-assembly approach of tissue engineering were used to assess the formation of capillary-like structures. Quite interestingly, this innovative in vitro model of MMD recapitulated, for the first time, disease-associated pathophysiological features such as significant increase in angiogenesis in confluent endothelial cells devoid of RNF213 expression. These cells, grown to confluence, also showed a pro-angiogenic signature, i.e., increased secretion of soluble pro-angiogenic factors, that could be eventually used as biomarkers. Interestingly, we demonstrated that that these MMD-associated phenotypes are dependent of the cellular state, as only noted in confluent cells and not in proliferative RNF213-deficient cells.

Association of rare RNF213 variants and intracranial aneurysm risk in a Chinese population

Background

Genetic factors play important roles in the development of intracranial aneurysm (IA). Rare RNF213 variants have been identified as being susceptible to Moyamoya disease (MMD), non-MMD intracranial artery stenosis/occlusion disease, and other vascular disorders. This study aimed to investigate the association between rare RNF213 variants and the risk of IA in a Chinese population.

Methods

We recruited 174 patients with IA for RNF213 target exome sequencing. Information on the control subjects was obtained from the 1,000 Genome Project and GeneSky in-house database. After prioritizing rare RNF213 variants, the filtered variants were confirmed by Sanger sequencing. Gene-based association analyses were performed to identify the association between variants and the disease using burden and variance component methods; that is, the weighted-sum statistic (WSS) and the sequence kernel association test (SKAT), respectively. The Student's t-test, Chi-squared test, and Fisher's exact test were used to compare the clinical characteristics between carriers and non-carriers of the RNF213 variants.

Results

After filtering, there were 14 RNF213 variants in 18 patients with IA, which were significantly associated with the disease after the gene-based association tests [minor allele frequency (MAF) <0.01, WSS P value 5.08×10^-9; SKAT P value 2.96×10^-6; SKAT-O P value 3.56×10^-8]. Significant difference was not obtained between the carriers and non-carriers of the RNF213 variants in terms of the clinical characteristics.

Conclusions

Rare RNF213 variants were associated with sporadic IA in a Chinese population. Our findings suggest that these rare RNF213 variants might have potentially important roles in IA. However, more comprehensive studies need to be conducted to confirm this association and causality.

Research progress of moyamoya disease combined with renovascular hypertension

Moyamoya disease (MMD) is an idiopathic cerebrovascular disease which was first described by Suzuki and Takaku in 1969. Moyamoya disease is a non-atherosclerotic cerebrovascular structural disorder. MMD has been found all over the world, especially in Japan, Korea, and China. In recent years, many reports pointed out that the changes of vascular stenosis in patients with moyamoya disease occurred not only in intracranial vessels, but also in extracranial vessels, especially the changes of renal artery. Renovascular hypertension (RVH) is considered to be one of the important causes of hypertension in patients with moyamoya disease. The pathogenesis of moyamoya disease combined with renovascular hypertension is still unclear, and the selection of treatment has not yet reached a consensus. This article reviews the latest research progress in epidemiology, RNF213 gene, pathomorphology, clinical characteristics and treatment of moyamoya disease combined with renovascular hypertension, in order to provide reference for clinical workers.

Novel Multifaceted Roles for RNF213 Protein

Ring Finger Protein 213 (RNF213), also known as Mysterin, is the major susceptibility factor for Moyamoya Arteriopathy (MA), a progressive cerebrovascular disorder that often leads to brain stroke in adults and children. Although several rare RNF213 polymorphisms have been reported, no major susceptibility variant has been identified to date in Caucasian patients, thus frustrating the attempts to identify putative therapeutic targets for MA treatment. For these reasons, the investigation of novel biochemical functions, substrates and unknown partners of RNF213 will help to unravel the pathogenic mechanisms of MA and will facilitate variant interpretations in a diagnostic context in the future. The aim of the present review is to discuss novel perspectives regarding emerging RNF213 roles in light of recent literature updates and dissect their relevance for understanding MA and for the design of future research studies. Since its identification, RNF213 involvement in angiogenesis and vasculogenesis has strengthened, together with its role in inflammatory signals and proliferation pathways. Most recent studies have been increasingly focused on its relevance in antimicrobial activity and lipid metabolism, highlighting new intriguing perspectives. The last area could suggest the main role of RNF213 in the proteasome pathway, thus reinforcing the hypotheses already previously formulated that depict the protein as an important regulator of the stability of client proteins involved in angiogenesis. We believe that the novel evidence reviewed here may contribute to untangling the complex and still obscure pathogenesis of MA that is reflected in the lack of therapies able to slow down or halt disease progression and severity.

Ring Finger Protein 213 in Moyamoya Disease With Pulmonary Arterial Hypertension: A Mini-Review

Moyamoya disease (MMD), most often diagnosed in children and adolescents, is a chronic cerebrovascular disease characterized by progressive stenosis at the terminal portion of the internal carotid artery and an abnormal vascular network at the base of the brain. Recently, many investigators show a great interest in MMD with pulmonary arterial hypertension (PAH). Ring finger protein 213 (RNF213) is a major susceptibility gene for MMD and also has strong correlations with PAH. Therefore, this review encapsulates current cases of MMD with PAH and discusses MMD with PAH in the aspects of epidemiology, pathology, possible pathogenesis, clinical manifestations, diagnosis, and treatment.

CRISPR Detection and Research on Screening Mutant Gene TTN of Moyamoya Disease Family Based on Whole Exome Sequencing

Moyamoya disease (MMD) has a high incidence in Asian populations and demonstrates some degree of familial clustering. Whole-exome sequencing (WES) is useful in establishing key related genes in familial genetic diseases but is time-consuming and costly. Therefore, exploring a new method will be more effective for the diagnosis of MMD. We identified familial cohorts showing MMD susceptibility and performed WES on 5 affected individuals to identify susceptibility loci, which identified point mutation sites in the titin (TTN) gene (rs771533925, rs559712998 and rs72677250). Moreover, TTN mutations were not found in a cohort of 50 sporadic MMD cases. We also analyzed mutation frequencies and used bioinformatic predictions to reveal mutation harmfulness, functions and probabilities of disease correlation, the results showed that rs771533925 and rs72677250 were likely harmful mutations with GO analyses indicating the involvement of TTN in a variety of biological processes related to MMD etiology. CRISPR-Cas12a assays designed to detect TTN mutations provided results consistent with WES analysis, which was further confirmed by Sanger sequencing. This study recognized TTN as a new familial gene marker for moyamoya disease and moreover, demonstrated that CRISPR-Cas12a has the advantages of rapid detection, low cost and simple operation, and has broad prospects in the practical application of rapid detection of MMD mutation sites.

MMD-associated RNF213 SNPs encode dominant-negative alleles that globally impair ubiquitylation

MMD-associated SNPs of RNF213 encode dominant-negative alleles that globally impair ubiquitylation by RNF213-UBE2D2.

Single-nucleotide polymorphisms (SNPs) in RNF213, which encodes a 591-kD protein with AAA+ ATPase and RING E3 domains, are associated with a rare, autosomal dominant cerebrovascular disorder, moyamoya disease (MMD). MMD-associated SNPs primarily localize to the C-terminal region of RNF213, and some affect conserved residues in the RING domain. Although the autosomal dominant inheritance of MMD could most easily explained by RNF213 gain-of-function, the type of ubiquitylation catalyzed by RNF213 and the effects of MMD-associated SNPs on its E3 ligase activity have remained unclear. We found that RNF213 uses the E2-conjugating enzymes UBE2D2 and UBE2L3 to catalyze distinct ubiquitylation events. RNF213-UBED2 catalyzes K6 and, to a lesser extent, K48-dependent poly-ubiquitylation in vitro, whereas RNF213-UBE2L3 catalyzes K6-, K11-, and K48-dependent poly-ubiquitylation events. MMD-associated SNPs encode proteins with decreased E3 activity, and the most frequent MMD allele, RNF213^R4810K, is a dominant-negative mutant that decreases ubiquitylation globally. By contrast, MMD-associated RNF213 SNPs do not affect ATPase activity. Our results suggest that decreased RNF213 E3 ligase activity is central to MMD pathogenesis.

Moyamoya Disease Susceptibility Gene RNF213 Regulates Endothelial Barrier Function

BACKGROUND

Variants in the ring finger protein 213 (RNF213) gene are known to be associated with increased predisposition to cerebrovascular diseases development. Genomic studies have identified RNF213 as a major risk factor of Moyamoya disease in East Asian descendants. However, little is known about the RNF213 (ring finger protein 213) biological functions or its associated pathogenic mechanisms underlying Moyamoya disease.

METHODS

To investigate RNF213 loss-of-function effect in endothelial cell, stable RNF213-deficient human cerebral endothelial cells were generated using the CRISPR-Cas9 genome editing technology.

RESULTS

In vitro assays, using RNF213 knockout brain endothelial cells, showed clear morphological changes and increased blood-brain barrier permeability. Downregulation and delocalization of essential interendothelial junction proteins involved in the blood-brain barrier maintenance, such as PECAM-1 (platelet endothelial cell adhesion molecule-1), was also observed. Brain endothelial RNF213-deficient cells also showed an abnormal potential to transmigration of leukocytes and secreted high amounts of proinflammatory cytokines.

CONCLUSIONS

Taken together, these results indicate that RNF213 could be a key regulator of cerebral endothelium integrity, whose disruption could be an early pathological mechanism leading to Moyamoya disease. This study also further reinforces the importance of blood-brain barrier integrity in the development of Moyamoya disease and other RNF213-associated diseases.

Proteome Profiling of RNF213 Depleted Cells Reveals Nitric Oxide Regulator DDAH1 Antilisterial Activity

RNF213 is a large, poorly characterized interferon-induced protein. Mutations in RNF213 are associated with predisposition for Moyamoya disease (MMD), a rare cerebrovascular disorder. Recently, RNF213 was found to have broad antimicrobial activity in vitro and in vivo, yet the molecular mechanisms behind this function remain unclear. Using mass spectrometry-based proteomics and validation by real-time PCR we report here that knockdown of RNF213 leads to transcriptional upregulation of MVP and downregulation of CYR61, in line with reported pro- and anti-bacterial activities of these proteins. Knockdown of RNF213 also results in downregulation of DDAH1, which we discover to exert antimicrobial activity against Listeria monocytogenes infection. DDAH1 regulates production of nitric oxide (NO), a molecule with both vascular and antimicrobial effects. We show that NO production is reduced in macrophages from RNF213 KO mice, suggesting that RNF213 controls Listeria infection through regulation of DDAH1 transcription and production of NO. Our findings propose a potential mechanism for the antilisterial activity of RNF213 and highlight NO as a potential link between RNF213-mediated immune responses and the development of MMD.

The AAA+ superfamily: a review of the structural and mechanistic principles of these molecular machines

ATPases associated with diverse cellular activities (AAA+ proteins) are a superfamily of proteins found throughout all domains of life. The hallmark of this family is a conserved AAA+ domain responsible for a diverse range of cellular activities. Typically, AAA+ proteins transduce chemical energy from the hydrolysis of ATP into mechanical energy through conformational change, which can drive a variety of biological processes. AAA+ proteins operate in a variety of cellular contexts with diverse functions including disassembly of SNARE proteins, protein quality control, DNA replication, ribosome assembly, and viral replication. This breadth of function illustrates both the importance of AAA+ proteins in health and disease and emphasizes the importance of understanding conserved mechanisms of chemo-mechanical energy transduction. This review is divided into three major portions. First, the core AAA+ fold is presented. Next, the seven different clades of AAA+ proteins and structural details and reclassification pertaining to proteins in each clade are described. Finally, two well-known AAA+ proteins, NSF and its close relative p97, are reviewed in detail.

Ring finger protein 213 assembles into a sensor for ISGylated proteins with antimicrobial activity

ISG15 is an interferon-stimulated, ubiquitin-like protein that can conjugate to substrate proteins (ISGylation) to counteract microbial infection, but the underlying mechanisms remain elusive. Here, we use a virus-like particle trapping technology to identify ISG15-binding proteins and discover Ring Finger Protein 213 (RNF213) as an ISG15 interactor and cellular sensor of ISGylated proteins. RNF213 is a poorly characterized, interferon-induced megaprotein that is frequently mutated in Moyamoya disease, a rare cerebrovascular disorder. We report that interferon induces ISGylation and oligomerization of RNF213 on lipid droplets, where it acts as a sensor for ISGylated proteins. We show that RNF213 has broad antimicrobial activity in vitro and in vivo, counteracting infection with Listeria monocytogenes, herpes simplex virus 1, human respiratory syncytial virus and coxsackievirus B3, and we observe a striking co-localization of RNF213 with intracellular bacteria. Together, our findings provide molecular insights into the ISGylation pathway and reveal RNF213 as a key antimicrobial effector.

The Genetic Basis of Moyamoya Disease

Moyamoya disease (MMD) is a rare cerebrovascular disease characterized by progressive spontaneous bilateral occlusion of the intracranial internal cerebral arteries (ICA) and their major branches with compensatory capillary collaterals resembling a “puff of smoke” (Japanese: Moyamoya) on cerebral angiography. These pathological alterations of the vessels are called Moyamoya arteriopathy or vasculopathy and a further distinction is made between primary and secondary MMD. Clinical presentation depends on age and population, with hemorrhage and ischemic infarcts in particular leading to severe neurological dysfunction or even death. Although the diagnostic suspicion can be posed by MRA or CTA, cerebral angiography is mandatory for diagnostic confirmation. Since no therapy to limit the stenotic lesions or the development of a collateral network is available, the only treatment established so far is surgical revascularization. The pathophysiology still remains unknown. Due to the early age of onset, familial cases and the variable incidence rate between different ethnic groups, the focus was put on genetic aspects early on. Several genetic risk loci as well as individual risk genes have been reported; however, few of them could be replicated in independent series. Linkage studies revealed linkage to the 17q25 locus. Multiple studies on the association of SNPs and MMD have been conducted, mainly focussing on the endothelium, smooth muscle cells, cytokines and growth factors. A variant of the RNF213 gene was shown to be strongly associated with MMD with a founder effect in the East Asian population. Although it is unknown how mutations in the RNF213 gene, encoding for a ubiquitously expressed 591 kDa cytosolic protein, lead to clinical features of MMD, RNF213 has been confirmed as a susceptibility gene in several studies with a gene dosage-dependent clinical phenotype, allowing preventive screening and possibly the  development of new therapeutic approaches. This review focuses on the genetic basis of primary MMD only.

Protein Quality Control and Lipid Droplet Metabolism

Lipid droplets (LDs) are endoplasmic reticulum-derived organelles that consist of a core of neutral lipids encircled by a phospholipid monolayer decorated with proteins. As hubs of cellular lipid and energy metabolism, LDs are inherently involved in the etiology of prevalent metabolic diseases such as obesity and nonalcoholic fatty liver disease. The functions of LDs are regulated by a unique set of associated proteins, the LD proteome, which includes integral membrane and peripheral proteins. These proteins control key activities of LDs such as triacylglycerol synthesis and breakdown, nutrient sensing and signal integration, and interactions with other organelles. Here we review the mechanisms that regulate the composition of the LD proteome, such as pathways that mediate selective and bulk LD protein degradation and potential connections between LDs and cellular protein quality control.

RNF213 p.R4810K (c.14429G > A) Variant Determines Anatomical Variations of the Circle of Willis in Cerebrovascular Disease

Introduction

Dysregulation of the RING finger protein 213 (RNF213) gene impairs vascular formation in experimental animal models. In addition, vascular abnormalities in the circle of Willis are associated with cerebrovascular disease. Here, we evaluated the relationship between the East Asian founder variant RNF213 p.R4810K and consequent anatomical variations in the circle of Willis in cerebrovascular disease.

Patients and Methods

The present study is an observational cross-sectional study. It included patients with acute anterior circulation non-cardioembolic stroke admitted to our institution within 7 days of symptom onset or last-known-well from 2011 to 2019, and those who participated in the National Cerebral and Cardiovascular Center Biobank. We compared anatomical variations of the vessels constituting the circle of Willis between RNF213 p.R4810K (c.14429G > A) variant carriers and non-carriers using magnetic resonance angiography and assessed the association between the variants and the presence of the vessels constituting the circle of Willis. Patients with moyamoya disease were excluded.

Results

Four hundred eighty-one patients [146 women (30%); median age 70 years; median baseline National Institutes of Health Stroke Scale score 5] were analyzed. The RNF213 p.R4810K variant carriers (n = 25) were more likely to have both posterior communicating arteries (PComAs) than the variant non-carriers (n = 456) (56% vs. 13%, P < 0.01). Furthermore, variant carriers were less likely to have an anterior communicating artery (AComA) than non-carriers (68% vs. 84%, P = 0.04). In a multivariate logistic regression analysis, the association of RNF213 p.R4810K variant carriers with the presence of both PComAs and the absence of AComA remained significant.

Conclusion

Our findings suggest that the RNF213 p.R4810K variant is an important factor in determining anatomical variations in the circle of Willis.

Progression in Moyamoya Disease: Clinical Feature, Neuroimaging Evaluation and Treatment

Moyamoya disease (MMD) is a chronic cerebrovascular disease characterized by progressive stenosis of the arteries of the circle of Willis, with the formation of collateral vascular network at the base of the brain. Its clinical manifestations are complicated. Numerous studies have attempted to clarify the clinical features of MMD, including its epidemiology, genetic characteristics, and pathophysiology. With the development of neuroimaging techniques, various neuroimaging modalities with different advantages have deepened the understanding of MMD in terms of structural, functional, spatial, and temporal dimensions. At present, the main treatment for MMD focuses on neurological protection, cerebral blood flow reconstruction, and neurological rehabilitation, such as pharmacological treatment, surgical revascularization, and cognitive rehabilitation. In this review, we discuss recent progress in understanding the clinical features, in the neuroimaging evaluation and treatment of MMD.

Mutations of RNF213 are responsible for sporadic cerebral cavernous malformation and lead to a mulberry-like cluster in zebrafish

Although familial forms of cerebral cavernous malformation are mainly attributed to three CCM genes (KRIT1, CCM2 and PDCD10), no mutation is identified in sporadic cerebral cavernous malformation cases with a unique lesion, indicating additional genes for sporadic cerebral cavernous malformation. To screen the candidate genes, we conducted whole exome sequencing in 31 sporadic cerebral cavernous malformation patients and 32 healthy controls, and identified 5 affected individuals carrying 6 heterozygous deleterious mutations in RNF213 but no RNF213 mutation in healthy individuals. To further confirm RNF213 was associated with cerebral cavernous malformation, we generated rnf213a homozygous knockout zebrafish and found mutation of rnf213a in zebrafish led to a mulberry-like cluster of disordered-flow vascular channels which was reminiscent of human cerebral cavernous malformation. In addition, we revealed kbtbd7 and anxa6 were significantly downregulated due to rnf213a mutation through transcriptomic sequencing and RT-qPCR analysis. Based on the mulberry-like phenotype partly rescued by mRNA of kbtbd7 as well as anxa6, we suggested that rnf213a promoted mulberry-like cluster via downregulation of kbtbd7 and anxa6. Altogether, we firstly demonstrate RNF213is a novel candidate gene for sporadic cerebral cavernous malformation and the mutation of rnf213a is responsible for the mulberry-like cluster in zebrafish.

A new syndrome of moyamoya disease, kidney dysplasia, aminotransferase elevation, and skin disease associated with de novo variants in RNF213

Ring‐finger protein 213 (RNF213) encodes a protein of unknown function believed to play a role in cellular metabolism and angiogenesis. Gene variants are associated with susceptibility to moyamoya disease. Here, we describe two children with moyamoya disease who also demonstrated kidney disease, elevated aminotransferases, and recurrent skin lesions found by exome sequencing to have de novo missense variants in RNF213. These cases highlight the ability of RNF213 to cause Mendelian moyamoya disease in addition to acting as a genetic susceptibility locus. The cases also suggest a new, multi‐organ RNF213‐spectrum disease characterized by liver, skin, and kidney pathology in addition to severe moyamoya disease caused by heterozygous, de novo C‐terminal RNF213 missense variants.

In silico explanation for the causalities of deleterious RNF213 SNPs in Moyamoya disease and insulin resistance

Moyamoya disease (MMD), a cerebrovascular disorder caused by the RNF213 gene, is a cerebrovascular, neurological disorder leading to ischemic strokes. Our previous work suggested that RNF213 might be involved in the pro-inflammatory TNFα-mediated insulin-resistance pathway in adipocytes. Insulin resistance can lead to cerebrovascular diseases and ischemic strokes. Though p. R4810 K has been reported as the founder mutation for Asian population with this disease, there are several mutations continuously reported in clinical diagnosis. We are interested to know whether these mutations can modulate insulin resistance. Also, we are intended to understand the causalities of RNF213 and its associated mutations in MMD. For this, we have adopted a computational approach to characterize RNF213 and its naturally occurring SNPs. Clinically reported SNPs and the predicted SNPs were analyzed for their pathogenicity and effect on the biological function of the protein. To increase accuracy, this was performed through three different analysis software (PROVEAN, SIFT, and SNAP2). The mutations that were found to be deleterious in all the three platforms were further analyzed for their effect on the thermal stability of the protein through I-mutant and iStable. It was found that R4810 K and other mutations decreased the thermodynamic stability of the protein. Loss of function of RNF213 was suggested in some reports. Contrary to this, some studies reported a gain of function state due to the R4810K mutation. To understand this we have measured the ligand-binding ability of this mutated protein through COFACTOR and COACH. An increase in ligand binding is always related to the functional stability of a protein. We have observed that the R4810K mutation might increase the iron-binding efficiency of the amino acid residues. This increase in binding was further validated by analyzing the binding efficiencies by docking. Since RNF213 was previously reported as a target for Protein Tyrosine Phosphatase 1B (PTP1B), we have also analyzed whether PTP1B-binding positions are susceptible to mutations. We have re-analyzed our earlier report on the differential expression pattern of RNF213 in cancer and obese samples. We have provided a detailed analysis of the most deleterious SNPs related to RNF213. Also, we provide a prediction for the loss of function and gain of function attributes of RNF213 and its predicted causalities in MMD and insulin resistance.

Genetic and Proteomic Contributions to the Pathophysiology of Moyamoya Angiopathy and Related Vascular Diseases

Rationale

This literature review describes the pathophysiological mechanisms of the current classes of proteins, cells, genes, and signaling pathways relevant to moyamoya angiopathy (MA), along with future research directions and implementation of current knowledge in clinical practice.

Objective

This article is intended for physicians diagnosing, treating, and researching MA.

Methods and Results

References were identified using a PubMed/Medline systematic computerized search of the medical literature from January 1, 1957, through August 4, 2020, conducted by the authors, using the key words and various combinations of the key words “moyamoya disease,” “moyamoya syndrome,” “biomarker,” “proteome,” “genetics,” “stroke,” “angiogenesis,” “cerebral arteriopathy,” “pathophysiology,” and “etiology.” Relevant articles and supplemental basic science articles published in English were included. Intimal hyperplasia, medial thinning, irregular elastic lamina, and creation of moyamoya vessels are the end pathologies of many distinct molecular and genetic processes. Currently, 8 primary classes of proteins are implicated in the pathophysiology of MA: gene-mutation products, enzymes, growth factors, transcription factors, adhesion molecules, inflammatory/coagulation peptides, immune-related factors, and novel biomarker candidate proteins. We anticipate that this article will need to be updated in 5 years.

Conclusion

It is increasingly apparent that MA encompasses a variety of distinct pathophysiologic conditions. Continued research into biomarkers, genetics, and signaling pathways associated with MA will improve and refine our understanding of moyamoya’s complex pathophysiology. Future efforts will benefit from multicenter studies, family-based analyses, comparative trials, and close collaboration between the clinical setting and laboratory research.

UBC13 is an RNF213-associated E2 ubiquitin-conjugating enzyme, and Lysine 63-linked ubiquitination by the RNF213-UBC13 axis is responsible for angiogenic activity

Moyamoya disease (MMD) is a cryptogenic vascular disorder in the intracranial arteries. RING protein 213 (RNF213) is the susceptibility gene for MMD, and encodes a RING domain and a Walker motif. Herein, we identified UBC13 (UBE2N) as an E2 ubiquitin‐conjugating enzyme for RNF213 E3 ubiquitin ligase by yeast two‐hybrid screening with a fragment containing RNF213 RING domain as bait, and the immunocomplex of RNF213‐UBC13 was detected in vivo. Analysis of the ubiquitin chain on RNF213 by monitoring autoubiquitination showed that RNF213 was autoubiquitinated in a K63 chain fashion, but not in a K48 chain fashion. Finally, this RNF213 ubiquitination in a UBC13‐dependent manner was required for cell mobility and invasion activity for HUVEC cells in UBC13 knock‐down and ubiquitination‐dead RNF213 mutant expressing experiments. These findings demonstrated that RNF213 is a K63‐linked E3 ubiquitin ligase, and UBC13 is responsible for RNF213 dependent ubiquitination. The RNF213‐UBC13 axis may be associated with angiogenic activity and MMD.

The ring finger protein 213 gene (Rnf213) contributes to Rift Valley fever resistance in mice

Rift Valley fever (RVF) is an emerging viral zoonosis that primarily affects ruminants and humans. We have previously shown that wild-derived MBT/Pas mice are highly susceptible to RVF virus and that part of this phenotype is controlled by a locus located on distal Chromosome 11. Using congenic strains, we narrowed down the critical interval to a 530 kb region containing five protein-coding genes among which Rnf213 emerged as a potential candidate. We generated Rnf213-deficient mice by CRISPR/CAS9 on the C57BL/6 J background and showed that they were significantly more susceptible to RVF than control mice, with an average survival time post-infection reduced from 7 to 4 days. The human RNF213 gene had been associated with the cerebrovascular Moyamoya disease (MMD or MYMY) but the inactivation of this gene in the mouse resulted only in mild anomalies of the neovascularization. This study provides the first evidence that the Rnf213 gene may also impact the resistance to infectious diseases such as RVF.

New insights into TNFα/PTP1B and PPARγ pathway through RNF213- a link between inflammation, obesity, insulin resistance, and Moyamoya disease

Diabetic patients are always at a higher risk of ischemic diseases like coronary artery diseases. One such ischemic carotid artery disease is Moyamoya disease (MMD) associated with diabetes Type I and II, but the causality was unclear. Ring Finger Protein 213 (RNF213) is the major susceptible gene for MMD. To understand the association between diabetes mellitus and MMD we chose the major players from both of the anomalies: insulin and RNF213. But before establishing the role of RNF213 in the insulin-regulating pathway we had to understand the involvement of RNF213 within different biological systems. For this, we have adopted a preliminary computational approach to find the prominent interactions of RNF213. Our first objective was to construct an interactome for RNF213. We have analyzed several curated databases and adapted a list of RNF213 interacting partners to develop its interactome. Then to understand the involvement of this interactome in biological functions we have analyzed major biological pathways, biological processes, and prominent clusters related to this interactome through a computational approach. Then to develop a pathway that might give clues for RNF213 involvement in the insulin regulatory pathway we have validated the intercluster and intracluster predictions and identified a regulatory pathway for RNF213. RNF213 interactome was observed to be involved in adaptive immunity with 4 major clusters; one of the clusters involved TNFα. The immune system involves several pathways, and therefore at this point, we have chosen an event-based strategy to obtain an explicit target. Immunity is mediated by pro-inflammatory cytokines like TNFα. TNFα-mediated inflammation, obesity, and insulin resistance are associated. Therefore we chose to explore the role of RNF213 in TNFα-mediated inflammation in macrophages and inflammation-mediated insulin-resistance in adipocytes. We have observed an enhancement of RNF213 gene expression by LPS mediated pro-inflammatory stimuli and suppression by PPARγ-mediated anti-inflammatory, insulin-sensitizing stimuli in macrophages, and also in adipocytes. Administration of the pro-inflammatory cytokine TNFα was able to impede the reduction in RNF213 expression during adipogenesis and this effect was observed to be mediated by PTP1B. Inactivation of PTP1B abolished RNF213 expression which in turn enhanced the adipogenesis process through enhanced PPARγ. Constitutive expression of RNF213 suppressed the adipocyte differentiation by the inhibition of PPARγ. We could show the regulation of RNF213 by TNFα/PTP1B pathway and PPARγ. The constitutive expression of RNF213 during adipogenesis appears to be an adipostatic measure that obese patients acquire to inhibit further adipogenesis. This is verified in silico by analyzing the gene expression data obtained from the Gene Expression Omnibus database, which showed a higher expression of RNF213 in adipose tissue samples of obese people. Overall this study gives new insights into the TNFα-mediated pathway in adipogenesis and suggests the role of RNF213 in adipogenesis via this pathway.

Novel candidate genes for ECT response prediction-a pilot study analyzing the DNA methylome of depressed patients receiving electroconvulsive therapy

Background

Major depressive disorder (MDD) represents a serious global health concern. The urge for efficient MDD treatment strategies is presently hindered by the incomplete knowledge of its underlying pathomechanism. Despite recent progress (highlighting both genetics and the environment, and thus DNA methylation, to be relevant for its development), 30–50% of MDD patients still fail to reach remission with standard treatment approaches. Electroconvulsive therapy (ECT) is one of the most powerful options for the treatment of pharmacoresistant depression; nevertheless, ECT remission rates barely reach 50% in large-scale naturalistic population-based studies. To optimize MDD treatment strategies and enable personalized medicine in the long- term, prospective indicators of ECT response are thus in great need. Because recent target-driven analyses revealed DNA methylation baseline differences between ECT responder groups, we analyzed the DNA methylome of depressed ECT patients using next-generation sequencing. In this pilot study, we did not only aim to find novel targets for ECT response prediction but also to get a deeper insight into its possible mechanism of action.

Results

Longitudinal DNA methylation analysis of peripheral blood mononuclear cells isolated from a cohort of treatment-resistant MDD patients (n = 12; time points: before and after 1st and last ECT, respectively) using a TruSeq-Methyl Capture EPIC Kit for library preparation, led to the following results: (1) The global DNA methylation differed neither between the four measured time points nor between ECT responders (n = 8) and non-responders (n = 4). (2) Analyzing the DNA methylation variance for every probe (=1476812 single CpG sites) revealed eight novel candidate genes to be implicated in ECT response (protein-coding genes: RNF175, RNF213, TBC1D14, TMC5, WSCD1; genes encoding for putative long non-coding RNA transcripts: AC018685.2, AC098617.1, CLCN3P1). (3) In addition, DNA methylation of two CpG sites (located within AQP10 and TRERF1) was found to change during the treatment course.

Conclusions

We suggest ten novel candidate genes to be implicated in either ECT response or its possible mechanism. Because of the small sample size of our pilot study, our findings must be regarded as preliminary.

Moyamoya disease factor RNF213 is a giant E3 ligase with a dynein-like core and a distinct ubiquitin-transfer mechanism

RNF213 is the major susceptibility factor for Moyamoya disease, a progressive cerebrovascular disorder that often leads to brain stroke in adults and children. Characterization of disease-associated mutations has been complicated by the enormous size of RNF213. Here, we present the cryo-EM structure of mouse RNF213. The structure reveals the intricate fold of the 584 kDa protein, comprising an N-terminal stalk, a dynein-like core with six ATPase units, and a multidomain E3 module. Collaboration with UbcH7, a cysteine-reactive E2, points to an unexplored ubiquitin-transfer mechanism that proceeds in a RING-independent manner. Moreover, we show that pathologic MMD mutations cluster in the composite E3 domain, likely interfering with substrate ubiquitination. In conclusion, the structure of RNF213 uncovers a distinct type of an E3 enzyme, highlighting the growing mechanistic diversity in ubiquitination cascades. Our results also provide the molecular framework for investigating the emerging role of RNF213 in lipid metabolism, hypoxia, and angiogenesis.

Loss of mitochondrial ClpP, Lonp1, and Tfam triggers transcriptional induction of Rnf213, a susceptibility factor for moyamoya disease

Human RNF213, which encodes the protein mysterin, is a known susceptibility gene for moyamoya disease (MMD), a cerebrovascular condition with occlusive lesions and compensatory angiogenesis. Mysterin mutations, together with exposure to environmental trigger factors, lead to an elevated stroke risk since childhood. Mysterin is induced during cell stress, to function as cytosolic AAA+ ATPase and ubiquitylation enzyme. Little knowledge exists, in which context mysterin is needed. Here, we found that genetic ablation of several mitochondrial matrix factors, such as the peptidase ClpP, the transcription factor Tfam, as well as the peptidase and AAA+ ATPase Lonp1, potently induces Rnf213 transcript expression in various organs, in parallel with other components of the innate immune system. Mostly in mouse fibroblasts and human endothelial cells, the Rnf213 levels showed prominent upregulation upon Poly(I:C)-triggered TLR3-mediated responses to dsRNA toxicity, as well as upon interferon gamma treatment. Only partial suppression of Rnf213 induction was achieved by C16 as an antagonist of PKR (dsRNA-dependent protein kinase). Since dysfunctional mitochondria were recently reported to release immune-stimulatory dsRNA into the cytosol, our results suggest that mysterin becomes relevant when mitochondrial dysfunction or infections have triggered RNA-dependent inflammation. Thus, MMD has similarities with vasculopathies that involve altered nucleotide processing, such as Aicardi-Goutières syndrome or systemic lupus erythematosus. Furthermore, in MMD, the low penetrance of RNF213 mutations might be modified by dysfunctions in mitochondria or the TLR3 pathway.

Distribution of Intracranial Major Artery Stenosis/Occlusion According to RNF213 Polymorphisms

Intracranial major artery stenosis/occlusion (ICASO) is the major cause of ischemic stroke. Recent studies have suggested that variants of RNF213, a susceptibility gene for moyamoya disease (MMD), are also related to non-MMD ICASO. Regarding the predominant involvement of steno-occlusion on anterior circulation in MMD, we hypothesized that the ICASO distribution pattern (anterior/posterior) in non-MMD may differ according to RNF213 variants. This study analyzed 1024 consecutive Korean subjects without MMD who underwent computed tomography angiography (CTA) or magnetic resonance angiography (MRA). We evaluated four single nucleotide polymorphisms (SNPs) in the exon region of RNF213: 4448G > A (rs148731719), 4810G > A (rs112735431), 4863G > A (rs760732823), and 4950G > A (rs371441113). Associations between RNF213 variants and anterior/posterior ICASO were examined using multivariate logistic regression analysis. Anterior ICASO was present in 23.0% of study subjects, and posterior ICASO was present in 8.2%. The GA genotype of RNF213 4810G > A (adjusted odds ratio (AOR) [95% confidence interval (CI)], 2.39 [1.14–4.87] compared to GG; p = 0.018) and GA genotype of RNF213 4950G > A (AOR [95% CI], 1.71 [1.11–2.63] compared to GG; p = 0.015) were more frequent in subjects with anterior ICASO. The genotype frequency of RNF213 4863G > A differed significantly according to the presence of posterior ICASO. Further investigations of the functional and biological roles of RNF213 will improve our understanding of the pathomechanisms of ICASO and cerebrovascular disease.

Moyamoya disease patient mutations in the RING domain of RNF213 reduce its ubiquitin ligase activity and enhance NFκB activation and apoptosis in an AAA+ domain-dependent manner

Moyamoya disease (MMD) is a cerebrovascular disease characterized by progressive occlusion of the internal carotid arteries. Genetic studies originally identified RNF213 as an MMD susceptibility gene that encodes a large 591 kDa protein with a functional RING domain and dual AAA+ ATPase domains. As the functions of RNF213 and its relationship to MMD onset are unknown, we set out to characterize the ubiquitin ligase activity of RNF213, and the effects of MMD patient mutations on these activities and on other cellular processes. In vitro ubiquitination assays, using the RNF213 RING domain, identified Ubc13/Uev1A as a key ubiquitin conjugating enzyme that together generate K63-linked polyubiquitin chains. However, nearly all MMD patient mutations in the RING domain greatly reduced this activity. When full-length proteins were overexpressed in HEK293T cells, patient mutations that abolished the ubiquitin ligase activities conversely enhanced nuclear factor κB (NFκB) activation and induced apoptosis accompanied with Caspase-3 activation. These induced activities were dependent on the RNF213 AAA+ domain. Our results suggest that the NFκB- and apoptosis-inducing functions of RNF213 may be negatively regulated by its ubiquitin ligase activity and that disruption of this regulation could contribute towards MMD onset.

RNF213 suppresses carcinogenesis in glioblastoma by affecting MAPK/JNK signaling pathway

PURPOSE

Glioblastoma is the most common malignant brain tumor in central nervous system. Due to absence of the mechanism underlying glioblastoma, the clinical outcome is poor. RNF213 is a ring finger protein and mutation in RNF213 gene is detected in cancers. But the role of RNF213 in glioblastoma is unknown.

METHODS

RNF213 expression was detected by qPCR, western blotting, IHC technology. RNF213 was overexpressed in plasmid pcDNA3.1. Assays including CCK-8, plate colony formation, wound healing, transwell and FITC/PI dye were used to detect cell behaviors.

RESULTS

RNF213 was shown to express much lower in tumor tissues and in tumor cell lines compared to control. The patients with higher RNF213 expression displayed longer survival time. When RNF213 was overexpressed in U87MG cells, cell proliferation and colony formation were inhibited significantly. The ability of cell migration and invasion was also suppressed. FAC analysis demonstrated that cell apoptosis was increased after RNF213 overexpression. But cell cycle distribution was not affected by RNF213. Then the expression level of MEKK1, JNK, c-Jun, and cdc42 was decreased after RNF213 overexpression, but increased reversely when RNF213 was knocked down by RNAi technology.

CONCLUSIONS

RNF213 suppresses carcinogenesis and affects MAPK/JNK signaling pathway in glioblastoma. This study suggests that RNF213 might be a promising target for therapy of glioblastoma.

Observation of p.R4810K, a Polymorphism of the Mysterin Gene, the Susceptibility Gene for Moyamoya Disease, in Two Female Japanese Diabetic Patients with Familial Partial Lipodystrophy 1

Mysterin, which was recently shown to play an important role in maintaining cellular fat storage, has been identified to be the susceptibility gene for moyamoya disease (MMD). We encountered some female Japanese patients with partial lipodystrophy and MMD-like vascular lesions. This prompted us to examine whether mysterin variants may be present in these patients. We identified a mysterin variant, p.R4810K in two patients with MMD-like vascular lesions, who may fit the category of familial partial lipodystrophy (FPLD) 1. Our cases suggest the possibility that p.R4810K, in addition to atherogenic risk factors, might thus play a role in the development of atherosclerotic lesions in patients with FPLD1 and p.R4810K.

The Impact of Moyamoya Disease and RNF213 Mutations on the Spectrum of Plasma Protein and MicroRNA

Moyamoya disease (MMD) is a rare cerebrovascular disorder characterized by occlusion of bilateral internal carotid and intracerebral arteries with the compensatory growth of fragile small vessels. MMD patients develop recurrent infarctions in the basal ganglia and subcortical regions. Symptoms include transient ischemic attack or stroke, seizures, and headaches, which may occur suddenly or in a stepwise progression. Mutations in Ring Finger Protein 213 (RNF213), a Zinc ring finger protein, have been identified in some MMD patients but the etiology of MMD is still largely unknown. To gain insight into the pathophysiology of MMD, we characterized the impact of the RNF213 mutations on plasma protein and RNA profiles. Isobaric tags for relative and absolute quantitation and proximity extension assay were used to characterize the plasma proteome. Next generation sequencing-based small RNAseq was used to analyze the cell-free small RNAs in whole plasma and RNA encapsulated in extracellular vesicles. The changes of miRNAs and proteins identified are associated with signaling processes including angiogenesis and immune activities which may reflect the pathology and progression of MMD.

Novel missense variants in the RNF213 gene from a European family with Moyamoya disease

In this report, we present a European family with six individuals affected with Moyamoya disease (MMD). We detected two novel missense variants in the Moyamoya susceptibility gene RNF213, c.12553A>G (p.(Lys4185Glu)) and c.12562G>A (p.(Ala4188Thr)). Cosegregation of the variants with MMD, as well as a previous report of a variant affecting the same amino acid residue in unrelated MMD patients, supports the role of RNF213 in the pathogenesis of MMD.

DNA Methylation Analysis Identifies Differentially Methylated Sites Associated with Early-Onset Intracranial Atherosclerotic Stenosis

Aim: Studies have suggested that genetic and environmental factors do not account for all risks and mechanisms of intracranial atherosclerotic stenosis (ICAS). DNA methylation may play a role in the progression of ICAS.

Methods: DNA methylation profiles of peripheral blood leucocytes from 7 patients with early-onset ICAS and 7 perfectly matched controls were interrogated for the first time using the Illumina Infinium Human MethylationEPIC BeadChip. Afterward, functional analysis for differentially methylated genes was conducted. In addition, pyrosequencing verification was performed in an independent cohort comprising 21 patients with earlyonset ICAS and 21 age- and gender-matched controls.

Results: A total of 318 cytosine-phosphate-guanine sites were found to be differentially methylated based on the established standards. Functional analysis annotated differentially methylated sites to atherosclerosis-related processes and pathways, such as the negative regulation of hydrolase activity (GO 0051346), type II diabetes mellitus (KEGG hsa04930), and the insulin signaling pathway (KEGG hsa04910). In addition, a differentially methylated site was also validated, cg22443212 in gene Rnf213, which showed significant hypermethylation in patients with early-onset ICAS compared with controls 59.56% (49.77%, 88.55%) vs. 44.65% (25.07%, 53.21%), respectively; P = 0.010). Receiver operating characteristic curve analysis showed that the area under the curve value of cg22443212 was 0.744 (95% confidence interval, 0.586–0.866; P = 0.002).

Conclusions: We revealed that altered DNA methylation may play a role in the occurrence and development of ICAS. These results provided new epigenetic insights into ICAS.

The AAA+ ATPase/ubiquitin ligase mysterin stabilizes cytoplasmic lipid droplets

Mutations in mysterin cause cerebrovascular moyamoya, but the mechanism of pathogenesis is unknown. Sugihara et al. report that mysterin stabilizes cytoplasmic lipid droplets through the activity of ATPase and ubiquitin ligase. Disease-associated mutations in mysterin impair this process, suggesting a potential link between moyamoya disease and metabolism.

Mysterin, also known as RNF213, is an intracellular protein that forms large toroidal oligomers. Mysterin was originally identified in genetic studies of moyamoya disease (MMD), a rare cerebrovascular disorder of unknown etiology. While mysterin is known to exert ubiquitin ligase and putative mechanical ATPase activities with a RING finger domain and two adjacent AAA+ modules, its biological role is poorly understood. Here, we report that mysterin is targeted to lipid droplets (LDs), ubiquitous organelles specialized for neutral lipid storage, and markedly increases their abundance in cells. This effect was exerted primarily through specific elimination of adipose triglyceride lipase (ATGL) from LDs. The ubiquitin ligase and ATPase activities of mysterin were both important for its proper LD targeting. Notably, MMD-related mutations in the ubiquitin ligase domain of mysterin significantly impaired its fat-stabilizing activity. Our findings identify a unique new regulator of cytoplasmic LDs and suggest a potential link between the pathogenesis of MMD and fat metabolism.

RNF213 Variant Diversity Predisposes Distinct Populations to Dissimilar Cerebrovascular Diseases

In recent years, the ring finger protein 213 gene (RNF213) has gradually attracted attention, mainly because it has been found that RNF213 c.14429 G>A is associated with moyamoya disease (MMD) in East Asian populations. Recent studies have revealed that RFN213 is not only associated with MMD but is also connected with intracranial major artery stenosis/occlusion (ICASO) and intracranial aneurysm (IA). However, only the relationship between RNF213 c.14429 G>A and ICASO has been confirmed, and whether RNF213 has other mutations related to ICASO remains unclear. RNF213 and IA are currently only confirmed to be correlated in French-Canadian Population and no correlation has been found in the Japanese population. This review summarizes the advances in the associations between RNF213 and different cerebrovascular diseases and highlights that variant diversity of RNF213 may predispose distinct populations to dissimilar cerebrovascular diseases.

RNF213 p.R4810K Polymorphism and the Risk of Moyamoya Disease, Intracranial Major Artery Stenosis/Occlusion, and Quasi-Moyamoya Disease: A Meta-Analysis

BACKGROUND

Accumulating studies have reported that there is an association between the Ring finger protein 213 (RNF213) p.R4810K (rs112735431, c.14576G>A) single nucleotide polymorphism and the predisposition of moyamoya disease (MMD), intracranial major artery stenosis/occlusion (ICASO), quasi-moyamoya disease (quasi-MMD), and other vascular diseases. However, to this day, analyses about this association have remained scarce in the literature. We attempted to conduct a meta-analysis to systematically summarize and clarify the issue.

METHODS

Electronic databases dated up to January 2018 were searched, retrieved, and used. Revman 5.2 software and STATA version 12.0 were used for statistical analysis. The association between RNF213 p.R4810K and MMD, ICASO, and quasi-MMD were assessed by odds ratios and 95% confidence intervals using fixed effects models. Between-study heterogeneity was evaluated by I-squared (I²) statistics and sensitivity analysis was performed by omitting 1 study at a time. A funnel plot and Begg's test were used to assess the potential publication bias.

RESULTS

The outcomes showed a statistically significant association between RNF213 p.R4810K and MMD, ICASO, and quasi-MMD, especially in the dominant model. Apart from the first 2 diseases, no significant association was identified under the recessive, the homozygote, and the heterozygote models in ICASO.

CONCLUSIONS

RNF213 p.R4810K was associated with MMD, ICASO, and quasi-MMD in different genetic models. Subgroup analysis indicated highly significantly higher risk in the Japanese patients. However, further well-designed studies with larger sample size and comprehensive data are needed to confirm our findings and provide a profound conclusion.

Rare variants in RNF213, a susceptibility gene for moyamoya disease, are found in patients with pulmonary hypertension and aggravate hypoxia-induced pulmonary hypertension in mice

Ring finger 213 (RNF213) is a susceptibility gene for moyamoya disease (MMD), a progressive cerebrovascular disease. Recent studies suggest that RNF213 plays an important role not only in MMD, but also in extracranial vascular diseases, such as pulmonary hypertension (PH). In this study, we undertook genetic screening of RNF213 in patients with PH and performed functional analysis of an RNF213 variant using mouse models. Direct sequencing of the exons in the C-terminal region of RNF213, where MMD-associated mutations are highly clustered, and of the entire coding exons of BMPR2 and CAV1, the causative genes for PH, was performed in 27 Japanese patients with PH. Two MMD-associated rare variants (p.R4810K and p.A4399T) in RNF213 were identified in two patients, three BMPR2 mutations (p.Q92H, p.L198Rfs*4, and p.S930X) were found in three patients, whereas no CAV1 mutations were identified. To test the effect of the RNF213 variants on PH, vascular endothelial cell (EC)-specific Rnf213 mutant transgenic mice were exposed to hypoxia. Overexpression of the EC-specific Rnf213 mutant, but neither Rnf213 ablation nor EC-specific wild-type Rnf213 overexpression, aggravated the hypoxia-induced PH phenotype (high right ventricular pressure, right ventricular hypertrophy, and muscularization of pulmonary vessels). Under hypoxia, electron microscopy showed unique EC detachment in pulmonary vessels, and western blots demonstrated a significant reduction in caveolin-1 (encoded by CAV1), a key molecule involved in EC functions, in lungs of EC-specific Rnf213 mutant transgenic mice, suggestive of EC dysfunction. RNF213 appears to be a genetic risk factor for PH and could play a role in systemic vasculopathy.

Dysregulation of RNF213 promotes cerebral hypoperfusion

RNF213 is a susceptibility gene for moyamoya disease, yet its exact functions remain unclear. To evaluate the role of RNF213 in adaptation of cerebral blood flow (CBF) under cerebral hypoperfusion, we performed bilateral common carotid artery stenosis surgery using external microcoils on Rnf213 knockout (KO) and vascular endothelial cell-specific Rnf213 mutant (human p.R4810K orthologue) transgenic (EC-Tg) mice. Temporal CBF changes were measured by arterial spin-labelling magnetic resonance imaging. In the cortical area, no significant difference in CBF was found before surgery between the genotypes. Three of eight (37.5%) KO mice died after surgery but all wild-type and EC-Tg mice survived hypoperfusion. KO mice had a significantly more severe reduction in CBF on day 7 than wild-type mice (KO, 29.7% of baseline level; wild-type, 49.3%; p = 0.038), while CBF restoration on day 28 was significantly impaired in both KO (50.0%) and EC-Tg (56.1%) mice compared with wild-type mice (69.5%; p = 0.031 and 0.037, respectively). Changes in the subcortical area also showed the same tendency as the cortical area. Additionally, histological analysis demonstrated that angiogenesis was impaired in both EC-Tg and KO mice. These results are indicative of the essential role of RNF213 in the maintenance of CBF.

Determination of diffusion coefficients in live cells using fluorescence recovery after photobleaching with wide-field fluorescence microscopy

Fluorescence recovery after photobleaching (FRAP) enables characterization of quantitative dynamic properties such as diffusion coefficients of fluorescent molecules in living cells by analyzing the recovery of fluorescence intensity after photobleaching in a specific cellular compartment or area. To quantitatively determine high intracellular diffusion coefficients, a suitable optical system as well as an appropriate model for fast diffusion analysis is necessary. Here, we propose a procedure to quantify the diffusion coefficient of rapidly-diffusing fluorescent molecules that makes use of an epi-fluorescence microscope with a photobleaching laser in combination with established models for diffusion analysis. Analysis for the diffusion coefficients of tandemly oligomerized green flurescent proteins (GFPs) in living cells when changing the photobleaching times showed that photobleaching with shorter times than the diffusion speed indicated not the only way to obtain appropriate diffusion coefficients of fast-moving molecules. Our results also showed that the apparent spreading of the effective radius of the photobleached area works as a correction factor for determining appropriate diffusion coefficients of fast-moving molecules like monomeric GFPs. Our procedure provides a useful approach for quantitative measurement of diffusion coefficients in living cells. This procedure is relevant for characterizing dynamic molecular interactions, especially of fast-moving molecules, and is relevant for studies in many biological fields.