circBase: a database for circular RNAs

CircMYO9A inhibits influenza A virus replication by dampening haemagglutinin cleavage via increasing SERPINE1/PAI-1 expression

Circular RNAs (circRNAs) represent a class of widespread and diverse covalently closed circular endogenous RNAs that play critical roles in regulating gene expression in mammals. However, the roles and regulatory mechanisms of circRNAs during influenza A virus (IAV) infection remain largely unexplored. In this study, we screened the circRNA transcription profiles of WSN-infected cells to identify circRNAs involved in viral replication and identified a novel differentially expressed circular RNA, circMYO9A. Mechanistically, circMYO9A acts as a competing endogenous RNA (ceRNA) for SERPINE1/PAI-1 by sponging miR-6059-3p, thereby increasing SERPINE1/PAI-1 expression, which restricts IAV haemagglutinin cleavage and subsequently reduces the infectivity of progeny viruses. Importantly, our findings demonstrate that circMYO9A significantly inhibits viral replication in the lungs of infected mice, potentially increasing their survival during IAV infection. These results demonstrate that circRNAs play crucial roles in inhibiting IAV replication and provide novel insights into potential therapeutic strategies involving circRNAs.

Comprehensive circRNA expression profile and hub genes screening during human liver development

BACKGROUND

Understanding the expression of non-coding RNA in the liver during embryonic development provides important insights into liver diseases. Therefore, we investigated circular RNA (circRNA) roles in human liver development, an unexplored research domain.

METHODS

Using high-throughput sequencing and bioinformatics, we analysed foetal liver samples across developmental stages (7-20 weeks post-conception). Differentially expressed (DE) genes were identified and subjected to enrichment analysis using Gene Ontology (GO), Kyoto Encyclopaedia of Genes and Genomes (KEGG), and Disease Ontology (DO). Modular analysis was performed using the Search Tool for Retrieval of Interacting Genes (STRING), followed by construction of a protein-protein interaction (PPI) network using Cytoscape software. The key genes were screened using Molecular Complex Detection (MCODE). The mRNA levels of hub genes were validated using quantitative reverse transcription polymerase chain reaction (qRT-PCR).

RESULTS

There were 645 DE circRNAs and 5,145 DE mRNAs between human livers at the three growth stages (HB, EH, and LH). It was found that the activity of circRNAs was boosted remarkably in the hepatoblastic stage. Enrichment analysis found they mainly involved in nervous system regulation of liver function, embryonic organ development and digestive system development. In addition, DE circRNAs were primarily involved in the PI3K-AKT, MAPK and calcium pathways, potentially contributing to adult liver diseases. Notably, only hsa_circ_001471 and novel_circ_017382 were simultaneously identified at all stages and were persistently downregulated. A co-expression regulatory network involving these circRNAs was established. Three hub genes (LGR5, FOXL1 and RSPO3) were identified from the PPI network of 167 genes and may play key roles in human liver development. The RT-qPCR validation results were in agreement with the sequencing data.

CONCLUSIONS

Our findings provide the first insights into the roles and regulatory networks of circRNAs in human liver development, laying the groundwork for further investigations of molecular and signalling networks.

Isoliquiritigenin reduces brain metastasis by circNAV3-ST6GALNAC5-EGFR axis in triple-negative breast cancer

Brain metastasis (BM) is a serious complication of increasing incidence in patients with advanced breast cancer, which is characterized by swift deterioration in quality of life with few efficient therapy strategies. There is an urgent clinical requirement to devise potent therapeutic strategies for the prevention and management of brain metastases. Here, we report isoliquiritigenin (ISL), a key bioactive substance extracted from licorice root, which effectively inhibited triple-negative breast cancer (TNBC) brain metastasis (BM) by downregulation of circNAV3. CircRNAs expression analyses and functional studies, coupled with clinical significance investigations identified circNAV3 as a key molecule promoting TNBC BM. Functionally, circNAV3 could promote proliferation, migration, invasion, angiogenesis and capacity to penetrate the blood-brain barrier of TNBC cells. Mechanistically, circNAV3 could competitively bind with miR-4262, hence intercepting the suppressive effect of miR-4262 on ST6GALNAC5. Subsequently, this interplay enhanced EGFR sialylation and activation, initiating the PI3K/Akt pathway and ultimately fostering the development of TNBC brain metastases. In conclusion, our research establishes that ISL impede the initiation and advancement of TNBC brain metastasis by modulation of circNAV3/miR-4262/ST6GALNAC5/EGFR axis, laying a theoretical groundwork for the therapeutic use of ISL in this scenario.

Dynamics and role of covalently-closed circular RNAs in Alzheimer's disease: A review of experimental and bioinformatics studies

Alzheimer's disease (AD) is an age-associated disorder characterized by cognitive decline, with dementia representing the final stage of a complex clinical-biological process rather than simply a more severe form of cognitive decline. Circular RNAs (circRNAs), novel non-coding RNAs, have emerged as key regulators of brain function and associated disorders. This study explores the role of circRNAs in AD by reviewing experimentally validated circRNAs in human and animal models. We identified 10 human (seven pathogenic, three protective) and six animal (three pathogenic, three protective) AD-related circRNAs. Experimental studies have confirmed that human protective circRNAs are predominantly downregulated in AD, where they function by sequestering specific miRNAs within cells, particularly miR-7, miR-142-5p, and miR-217, which have well-recognized neuroinflammatory functions. In-silico analysis revealed that circLPAR1 (pathogenic), circHUWE1 (pathogenic), and circHOMER1 (protective) interact with miRNAs that mainly control AD-related genes. Notably, circHOMER1 plays a key role in regulating multiple AD-related pathways, including autophagy, apoptosis, and PI3K-AKT and amyloid fiber formation. Furthermore, circRNA/protein interaction analysis revealed that circHUWE1 predominantly associates with RNA transport proteins, whereas circHOMER1 interacts with proteins involved in mRNA surveillance pathways. Remarkably, docking analysis demonstrated that circAβ-a (pathogenic) exhibits a strong affinity for eukaryotic translation initiation factor 4A3 protein, while circHOMER1 shows a higher binding affinity for DGCR8 microprocessor complex subunit protein. Our study presents a concise list of circRNAs as potential key targets for further investigation in AD research. Future experimental research is essential to uncover their precise mechanisms and assess their potential as biomarkers, offering promising avenues for developing interventions to alleviate cognitive decline in AD.

Arsenic-induced circASXL1 regulates 16HBE cell proliferation through the P65 signaling axis

Arsenic is a well-known environmental toxicant, strongly associated with severe toxicity across multiple organs, including the lungs. Circular RNAs (circRNAs) are critical in various cellular processes and linked to disease due to their highly stable covalent closed-loop structure, making them potential therapeutic targets. This study aimed to investigate the expression of circASXL1 under arsenic exposure and its role in 16HBE cell proliferation upon circASXL1 knockdown. Treatment with sodium arsenite increased circASXL1 expression in 16HBE cells, while metabolites had no effect. Notably, circASXL1 knockdown enhanced cell viability and proliferation, concomitant with coordinated activation of STAT3 and P65. Although the precise mechanism requires further validation, our Western blot analyses suggested that STAT3 activation may promote P65 transcriptional activity, as evidenced by upregulated expression of its downstream targets PCNA, BCL2, BCL-XL, and CIAP1. Intriguingly, combinatorial treatment with arsenic and circASXL1-specific siRNAs attenuated both cell proliferation and P65 activation. Our findings propose that arsenic modulates circASXL1 to engage STAT3-P65 crosstalk. This study establishes the arsenic-circASXL1 axis as a novel regulator of STAT3/P65 signaling networks, providing mechanistic insights for combating arsenic-induced pulmonary pathologies.

Whole-transcriptome sequencing in neural and non-neural tissues of a mouse model identifies miR-34a as a key regulator in SMA pathogenesis

Spinal muscular atrophy (SMA) is a severe neurodegenerative disorder caused by deficiency of survival of motor neuron (SMN). While significant progress has been made in SMA therapy by rescuing SMN expression, limited knowledge about SMN downstream genes has hindered the development of alternative therapies. Here, we conducted whole-transcriptome sequencing of spinal cord, heart, and liver tissues of a severe SMA mouse model at early postnatal ages to explore critical coding and non-coding RNAs (ncRNAs). A large number of differentially expressed RNAs (DE-RNAs) were obtained, including 2,771 mRNAs, 382 microRNAs (miRNAs), 1,633 long ncRNAs, and 1,519 circular RNAs. Through in-depth data mining, we unveiled deregulation of miR-34a in all tissues. Analysis of competitive endogenous RNA networks of DE-RNAs identified multiple novel targets of miR-34a including Spag5 mRNA, lncRNA00138536, and circRNA007386. Further in vitro studies using mouse myoblast and human cardiomyocyte cell lines showed that knockdown of SMN upregulated miR-34a-5p and overexpression of miR-34a-5p alone disrupted cell-cycle progression through regulating its targets, recapitulating gene expression patterns observed in cardiac tissue of SMA mice. Our results identified a critical miRNA involved in SMA pathology, which sheds insights into the molecular basis of widespread tissue abnormalities observed in severe forms of SMA.

MVGNCDA: Identifying Potential circRNA-Disease Associations Based on Multi-view Graph Convolutional Networks and Network Embeddings

Increasing evidences have indicated that circular RNAs play a crucial role in the onset and progression of various diseases. However, exploring potential disease-associated circRNAs using conventional experimental techniques remains both time-intensive and costly. Recently, various computational approaches have been developed to detect the circRNA-disease associations. Nevertheless, due to the sparsity of the data and the inefficient utilization of similarity representation, it is still a challenge to effectively detect unknown circRNA-disease associations using multisource data. In this work, we propose an innovative computational framework, MVGNCDA, which merges a multi-view graph convolutional network (GCN) and biased random walk-based network embeddings to evaluate potential circRNA-disease associations from multisource data. First, we calculate disease semantic similarity, circRNA functional similarity, and their Gaussian interaction profile (GIP) kernel and cosine similarity. MVGNCDA utilizes multi-view GCNs to extract local node embeddings of diseases and circRNAs in the context of multisource information. Then, we construct a heterogeneous network utilizing integrated similarity and verified circRNA-disease associations, which is subsequently used to learn global node embeddings. Furthermore, the final fused local and global node embeddings are decoded to evaluate the circRNA-disease associations using a bilinear decoder. The fivefold cross-validation results demonstrate that MVGNCDA outperforms existing methods across five public datasets. Moreover, case study also confirms that MVGNCDA is capable of efficiently identifying unknown circRNA-disease associations.

CR-deal: Explainable Neural Network for circRNA-RBP Binding Site Recognition and Interpretation

circRNAs are a type of single-stranded non-coding RNA molecules, and their unique feature is their closed circular structure. The interaction between circRNAs and RNA-binding proteins (RBPs) plays a key role in biological functions and is crucial for studying post-transcriptional regulatory mechanisms. The genome-wide circRNA binding event data obtained by cross-linking immunoprecipitation sequencing technology provides a foundation for constructing efficient computational model prediction methods. However, in existing studies, although machine learning techniques have been applied to predict circRNA-RBP interaction sites, these methods still have room for improvement in accuracy and lack interpretability. We propose CR-deal, which is an interpretable joint deep learning network that predicts the binding sites of circRNA and RBP through genome-wide circRNA data. CR-deal utilizes a graph attention network to unify sequence and structural features into the same view, more effectively utilizing structural features to improve accuracy. It can infer marker genes in the binding site through integrated gradient feature interpretation, thereby inferring functional structural regions in the binding site. We conducted benchmark tests on CR-deal on 37 circRNA datasets and 7 lncRNA datasets, respectively, and obtained the interpretability of CR-deal and discovered functional structural regions through 5 circRNA datasets. We believe that CR-deal can help researchers gain a deeper understanding of the functions and mechanisms of circRNA in living organisms and its critical role in the occurrence and development of diseases. The source code of CR-deal is provided free of charge on https://github.com/liuliwei1980/CR .

Targeting the Exonic Circular OGT RNA/O-GlcNAc Transferase/Forkhead Box C1 Axis Inhibits Asparagine- and Alanine-Mediated Ferroptosis Repression in Neuroblastoma Progression

The disruption of ferroptosis, an emerging form of programmed cell death, is crucial in the development and aggressiveness of tumors. Meanwhile, the mechanisms and treatments that control ferroptosis in neuroblastoma (NB), a prevalent extracranial cancer in children, are still unknown. In this study, forkhead box C1 (FOXC1) and O-GlcNAc transferase (OGT) are identified as regulators of asparagine- and alanine-mediated ferroptosis repression in NB. Mechanistically, OGT facilitates FOXC1 stabilization via inducing O-GlcNAcylation in liquid condensates to increase the expression of asparagine synthetase (ASNS) and glutamate pyruvate transaminase 2 (GPT2), resulting in asparagine and alanine biogenesis, and subsequent synthesis of cystathionine β-synthase (CBS) or ferritin heavy chain 1 (FTH1). Meanwhile, exonic circular OGT RNA (ecircOGT) is able to encode a novel protein (OGT-570aa) containing domain essential for binding of OGT to FOXC1, which competitively decreases the OGT-FOXC1 interaction. Preclinically, miconazole nitrate facilitates the interaction of OGT-570aa with FOXC1, suppresses ferroptosis resistance of NB cells, and inhibits their growth, invasion, and metastasis. In clinical NB cases, higher OGT, FOXC1, ASNS, GPT2, CBS, or FTH1 levels are correlated with worse survival, while lower ecircOGT or OGT-570aa expression is associated with tumor progression. These results indicate that targeting the ecircOGT/OGT/FOXC1 axis inhibits asparagine- and alanine-mediated ferroptosis repression in NB progression.

Structural determinants of inverted Alu-mediated backsplicing revealed by -MaP and -JuMP

Biogenesis of circular RNA usually involves a backsplicing reaction where the downstream donor site is ligated to the upstream acceptor site by the spliceosome. For this reaction to occur, these sites must be in proximity. Inverted repeat sequences, such as Alu elements, if positioned in the upstream and downstream introns, can base pair and represent one mechanism for inducing proximity. Here, we investigate the pre-mRNA structure of the human HIPK3 gene at exon 2, which forms a circular RNA via backsplicing. We leverage multiple chemical probing approaches, including the recently developed SHAPE-JuMP (selective 2'-hydroxyl acylation analyzed by primer extension and juxtaposed merged pairs) strategy, to characterize secondary and tertiary interactions in the pre-mRNA that govern backsplicing. Our data confirm that the antisense Alu elements AluSz(-) and AluSq2(+), in the upstream and downstream introns, form a highly paired interaction. Circularization requires formation of long-range Alu-mediated base pairs but does not require the full-length AluSq2(+). In addition to confirming long-range base pairs, our SHAPE-JuMP data identified multiple long-range interactions between non-pairing nucleotides. Genome-wide analysis of inverted repeats flanking circular RNAs confirms that the presence of these elements favors circularization, but with modest predictive power. Together, our study suggests that secondary structure considerations alone do not fully explain backsplicing and that additional interactions are involved.

Tumor cell-intrinsic circular RNA circFNDC3B attenuates CD8+ T cells infiltration in non-small cell lung cancer

Tumor-infiltrating CD8+ T cells are critical for anti-tumor immunity and positively associated with patient survival. However, the mechanisms governing CD8+ T cell infiltration remain incompletely elucidated, particularly those involving circular RNAs (circRNAs). In this study, we characterized circRNA expression profiles in four paired normal and tumor tissues of non-small-cell lung cancer (NSCLC) and identified that circFNDC3B, a circular transcript derived from exons 2 and 3 of the fibronectin type III domain containing 3B (FNDC3B) gene, as significantly upregulated in NSCLC tissues. Mechanistic investigations revealed that circFNDC3B directly binds to transcription factor II-I (TFII-I), forming an RNA-protein complex that competitively disrupts the interaction between TFII-I and STAT1. This sequestration abrogates the transcriptional activation of CXCL10 and CXCL11, two critical chemokines governing CD8+ T cell chemoattraction. Consequently, reduced CXCL10/11 expression significantly impairs CD8+ T cell infiltration into the tumor microenvironment. Consistently, the murine ortholog circFndc3b expression exhibits an inverse correlation with CD8+ T cell infiltration in tumors. Our study uncovers a crucial circRNA-mediated regulatory axis wherein circFNDC3B impedes anti-tumor immunity by suppressing chemokine-dependent CD8+ T cell recruitment, positioning circFNDC3B as a potential therapeutic target to enhance CD8+ T cell-mediated anti-tumor responses in NSCLC.

PDGF-BB promotes oral submucosal fibrosis by driving phenotypic transformation and autophagy in oral mucosal fibroblasts through downregulation of circHIPK3

Circular RNA HIPK3 (circHIPK3), known to regulate cell proliferation, migration, transformation, and autophagy in various fibrotic conditions. However, its role has not been studied in oral submucous fibrosis (OSF). Therefore, we conducted this study to explore whether platelet-derived growth factor-BB (PDGF-BB) induces human oral submucous fibroblasts (hOMF) proliferation, migration, transformation, and autophagy through circHIPK3 regulation. Treatment of hOMFs with PDGF-BB significantly increased circHIPK3 expression, promoting proliferation, migration, and autophagy. While inhibiting circHIPK3 mitigated these effects, confirming its role in PDGF-BB-mediated pathways. These findings reveal that PDGF-BB regulates hOMFs via circHIPK3, contributing to OSF pathogenesis and offering potential therapeutic targets. The molecular characteristics of circHIPK3 in fibroblasts (FBs) were identified by Agarose Gel Electrophoresis, Sanger Sequencing and Actinomycin D assay. Quantitative real-time PCR(RT-qPCR) and Western Blot were used to detect the expression of target molecules. The proliferation and migration capacity of FBs in oral mucosa were detected by the CCK8 and Cell Scratch Assay. Protein molecules interacting with circHIPK3 and downstream signaling pathways were screened by RNA pull down and mass spectrometry. Data are available via ProteomeXchange with identifier PXD062842. Firstly, the ring structure of circHIPK3 is verified. The expression level of circHIPK3 in OSF tissues and hOMFs was significantly decreased, while the expression level of circHIPK3 was significantly increased after inhibition of platelet-derived growth factor receptor beta‌‌ (PDGFR-β) by Imatinib (IMA). Subsequently, it was confirmed that the overexpression of circHIPK3 could effectively inhibit the proliferation, migration, transformation and autophagy of PDGF-BB-induced hOMFs. Finally, the mechanism study showed that circHIPK3 could inhibit the proliferation, migration, transformation and autophagy of hOMFs by regulating Y-box binding protein 1 (YBX1) protein and extracellular regulated protein kinases (ERK), phosphatidylinositol 3-kinase (PI3K) and p38 mitogen-activated protein kinase (p38 MAPK) signaling pathways. PDGF-BB downregulates circHIPK3 expression and induces proliferation, migration, transformation, and autophagy of oral mucosal FBs via the circHIPK3/YBX1 axis and the circHIPK3/ERK, PI3K, p38 MAPK axis.

Whole transcriptome sequencing-based identification and functional prediction of salt-tolerant-related circular RNAs in ZM-4 (Malus zumi)

CircRNAs, are a class of covalently closed non-coding RNAs; they have been identified in many plants and play an important role in the response to abiotic stresses. However, little is known about the response of the circRNAs of salt-tolerant apple rootstock resources in response to salt stress. In this study, the leaves and roots of the salt-tolerant Malus resource, ZM-4, and the salt-sensitive rootstock M9T337, were used as test materials and were exposed to 75 mmol/L NaCl stress for 0 h and 24 h. A total of 2502 circRNAs were identified, and 218 and 242 circRNAs were uniquely expressed in M9T337 and ZM-4, respectively. Furthermore, it was shown that the up-regulated parental genes of the differentially expressed circRNAs were enriched in the metabolic pathways and the biosynthesis of secondary metabolites pathway in the leaves and roots of ZM-4 under salt stress, respectively. There were potential regulatory networks of ceRNA among 150 circRNAs, 139 miRNAs, and 397 mRNAs. Novel_circ_000845 and novel_circ_000266 could target and inhibit the expression of mdm-miR156 and up-regulate the expression of the salt-responsive gene SPL6. Six circRNAs, including novel_circ_000898 and novel_circ_001519, could target and inhibit the expression of mdm-miR10995 and up-regulate the expression of the salt-responsive gene COBL7. In conclusion, this study laid the foundation for the post-transcriptional molecular regulation mechanism of salt tolerance in apple rootstock resources.

Circular RNA transcriptome across various development periods of Paralichthys olivaceus reveal skeletal muscle-specific circchd6 regulating myogenesis

The Japanese flounder (Paralichthys olivaceus) is greatly influenced in terms of muscle quality and quantity by the development of skeletal muscle. While the mechanisms underlying skeletal muscle development are well-studied, the role of non-coding RNAs, particularly circRNAs, in the skeletal muscle development of Japanese flounder remains unclear. To investigate the expression patterns of circRNAs during different developmental stages (JP1: 7 days, JP2: 90 days, JP3: 24 months (female), JP4: 24 months (male)) in Japanese flounder, we performed transcriptome sequencing analysis. We identified a total of 3523 circRNAs, of which 10.19 % were differentially expressed. These differentially expressed (DE) circRNAs were studied, and their impacts on muscle development were analyzed. The RNA interaction network revealed that skeletal muscle-specific circchd6 targeted novel-miR-508 and further regulated dual specificity tyrosine-phosphorylation regulated kinase 2 (dyrk2). Functional analysis showed that overexpressed circchd6 and dyrk2 promoted myoblast proliferation and differentiation, while novel-miR-508 inhibited both. Our study identified the circchd6-novel-miR-508-dyrk2 axis as a regulatory mechanism and provided new evidence for the use of epigenetic approaches in genetic breeding.

The emerging functions and clinical implications of circRNAs in acute myeloid leukaemia

Acute myeloid leukaemia (AML) is a prevalent haematologic malignancy characterized by significant heterogeneity. Despite the application of aggressive therapeutic approaches, AML remains associated with poor prognosis. Circular RNAs (circRNAs) constitute a unique class of single-stranded RNAs featuring covalently closed loop structures that are ubiquitous across species. These molecules perform crucial regulatory functions in the pathogenesis of various diseases through diverse mechanisms, including acting as miRNA sponges, interacting with DNA or proteins, and encoding functional proteins/polypeptides. Recently, numerous circRNAs have been confirmed to have aberrant expression patterns in AML patients. In particular, certain circRNAs are closely associated with specific clinicopathological characteristics and thus have great potential as diagnostic/prognostic biomarkers and therapeutic targets in AML. Herein, we systematically summarize the biogenesis, degradation, and functional mechanisms of circRNAs while highlighting their clinical relevance. We also outline a series of online databases and analytical tools available to facilitate circRNA research. Finally, we discuss the current challenges and future research priorities in this evolving field.

Collaborative Duality of CircGLIS3(2) RNA and Protein in human Wound Repair

The discovery of an increasing number of translatable circular RNAs (circRNAs) raises the question of whether their coding and non-coding functions can coexist within the same cell. This study profiles the dynamic expression of circRNAs during human skin wound healing. CircGLIS3(2) is identified, a circRNA whose levels transiently rise in dermal fibroblasts of acute wounds and are abnormally overexpressed in keloids, a fibrotic skin condition. Injury signals such as IL-1α, TGF-β, hypoxia, and ER stress induce both expression and cap-independent translation of CircGLIS3(2). The RNA form of CircGLIS3(2) activates fibroblasts into matrix-secreting cells, while its encoded protein promotes cell proliferation, collectively enhancing wound repair. Mechanistically, CircGLIS3(2) RNA stabilizes the cytoplasmic protein PCOLCE, while its protein binds to BTF3 in the nucleus. Both the RNA and protein are essential for wound closure in human and murine models. CircGLIS3(2)'s bifunctional nature expands its functional spectrum, improving cellular adaptability during environmental changes and offering a promising therapeutic target for wound repair and scar reduction.

Circular RNAs exhibit exceptional stability in the aging brain and serve as reliable age and experience indicators

Circular RNAs (circRNAs) increase in the brain with age across various animal systems. To elucidate the reasons behind this phenomenon, we profile circRNAs from fly heads at six time points throughout their lifespan. Our results reveal a linear increase in circRNA levels with age, independent of changes in mRNA levels, overall transcription, intron retention, or host gene splicing, demonstrating that the age-related accumulation is due to high stability rather than increased biogenesis. This remarkable stability suggests that circRNAs can serve as markers of environmental experience. Indeed, flies exposed to a 10-day regimen at 29°C exhibit higher levels of specific circRNAs even 6 weeks after returning to standard conditions, indicating that circRNAs can reveal past environmental stimuli. Moreover, half-life measurements show circRNA stability exceeding 20 days, with some displaying virtually no degradation. These findings underscore the remarkable stability of circRNAs in vivo and their potential as markers for stress and life experiences.

Molecular structure of VEGFA polysaccharide protein and its regulation of monocyte infiltration and oxidative stress after myocardial infarction

The pathogenesis of myocardial infarction (MI) is complex, involving multiple biomarkers and cell signaling pathways. The aim of this study was to elucidate the molecular structure of VEGFA dioglycan protein and explore how it regulates monocyte infiltration and oxidative stress response after myocardial infarction, so as to provide a new molecular target for the treatment of myocardial infarction. Differential expression analysis and enrichment analysis were performed to investigate the composition and characteristics of immune cells in myocardial infarction. The regulatory network was constructed by network analysis, and in vitro experiments were carried out by BMDM isolation culture. Animal experiments were conducted in mouse models, and data were verified and statistically analyzed by combining immunohistochemical staining, real-time PCR, Western blot and enzyme-linked immunosorbent assay (ELISA). Genome-wide association studies (GWAS) and single-cell data successfully identified key immune-related genes and analyzed differentially expressed mRNA and its characteristics in myocardial infarction. The immune microenvironment of myocardial infarction was investigated, the differentially expressed circRNA and miRNA were characterized, and the circrNa-mirNA-mrna regulatory network was constructed. The characteristics of differentially expressed proteins in myocardial infarction and the changes of mRNA during oxidative stress were identified and compared. By analyzing the changes in chromatin accessibility, the regulatory network between oxidative stress and myocardial infarction in immune cells was constructed, and the expression and co-localization of oxidative stress in myocardial infarction were verified.

Frequent dysregulation of multiple circular RNA isoforms with diverse regulatory mechanisms in cancer - Insights from circFNDC3B and beyond: Why unique circular RNA identifiers matter

Circular RNAs (circRNAs) are post-transcriptional regulators generated through backsplicing of pre-mRNAs, primarily comprising exons of host genes. A single host gene may produce multiple circRNA isoforms with distinct structures and sequences. Dysregulated circRNA expression has been implicated in tumorigenesis. This review aims to investigate the selection and regulatory roles of circRNA isoforms in cancer using the extensively studied hsa_circFNDC3B and thirteen other circRNAs as study models. Interrogation of literature and databases, particularly the circBase, confirms that host genes generate a plethora of circRNA isoforms; however, only a small subset of isoforms is validated as dysregulated in tumor tissues. Notably, two or more isoforms of the same circRNA are frequently dysregulated in cancer. Structurally, short isoforms retaining 5'-proximal exons are preferentially selected, but for long host genes, circRNAs may arise from mid- or 3'-regions. We identify dysregulation of seven circFNDC3B isoforms across twelve cancer types and multi-isoforms in nine of the other thirteen circRNAs also in multiple cancers. MicroRNA sponging appears to be the major regulatory mechanism, but possible biased study designs raise concerns. Using circFNDC3B and circZFR as examples, we show inconsistency and inadequacy in circRNA nomenclature in different databases and the literature, underscoring the urgent need for a universally accepted standardized central circRNA database. As an interim measure, we propose guidelines for circRNA nomenclature in journal publications. Our findings caution against indiscriminate clinical use of specific circRNA isoforms as biomarkers or therapeutic targets without further validation.

Unveiling Pharmacogenomics Insights into Circular RNAs: Toward Precision Medicine in Cancer Therapy

Pharmacogenomics is revolutionizing precision medicine by enabling tailored therapeutic strategies based on an individual genetic and molecular profile. Circular RNAs (circRNAs), a distinct subclass of endogenous non-coding RNAs, have recently emerged as key regulators of drug resistance, tumor progression, and therapeutic responses. Their covalently closed circular structure provides exceptional stability and resistance to exonuclease degradation, positioning them as reliable biomarkers and novel therapeutic targets in cancer management. This review provides a comprehensive analysis of the interplay between circRNAs and pharmacogenomics, focusing on their role in modulating drug metabolism, therapeutic efficacy, and toxicity profiles. We examine how circRNA-mediated regulatory networks influence chemotherapy resistance, alter targeted therapy responses, and impact immunotherapy outcomes. Additionally, we discuss emerging experimental tools and bioinformatics techniques for studying circRNAs, including multi-omics integration, machine learning-driven biomarker discovery, and high-throughput sequencing technologies. Beyond their diagnostic potential, circRNAs are being actively explored as therapeutic agents and drug delivery vehicles. Recent advancements in circRNA-based vaccines, engineered CAR-T cells, and synthetic circRNA therapeutics highlight their transformative potential in oncology. Furthermore, we address the challenges of standardization, reproducibility, and clinical translation, emphasizing the need for rigorous biomarker validation and regulatory frameworks to facilitate their integration into clinical practice. By incorporating circRNA profiling into pharmacogenomic strategies, this review underscores a paradigm shift toward highly personalized cancer therapies. circRNAs hold immense potential to overcome drug resistance, enhance treatment efficacy, and optimize patient outcomes, marking a significant advancement in precision oncology.

Identification of a circRNA-miRNA-mRNA interactome associated with Parkinson's disease progression

BackgroundCircular RNAs (circRNAs) constitute a distinctive subclass of RNAs that are known for their regulatory roles in fundamental cellular processes. Due to their increased stability and ubiquitous expression, circular RNAs have been widely studied as potential molecular targets in various diseases, including neurodegenerative diseases. While several studies have found differentially expressed circRNAs associated with Parkinson's disease (PD), none has looked specifically into PD progression.ObjectiveTo elucidate the role of circRNAs in the progression of PD by identifying dysregulated circRNAs associated with PD progression and to pinpoint potential downstream miRNAs and associated differentially expressed gene targets.MethodsIn this study, we have utilized large-scale, longitudinal, and deep RNA-seq data from two independent cohorts, namely the Parkinson's Progression Marker Initiative (PPMI) and the Parkinson's Disease Biomarker Program (PDBP), to characterize circRNA expression in patients of early PD stage.ResultsWe identified six circRNAs significantly differentially expressed in whole blood samples obtained from PD patients over time. Additionally, we were able to map a competing endogenous RNA (ceRNA) network with potential downstream miRNA-mRNA targets and, with the help of co-expression analysis, to identify genes associated with PD progression. Our findings provide compelling evidence for a dysregulated circRNA interactome as an indicator of PD progression, with changes in the expression of these circRNAs and downstream gene targets being significantly associated with changes in UPDRS III scores in PD patients.ConclusionsOur results strongly indicate the association of circular RNAs with PD progression and emphasize its significance as a critical molecular marker.

Circular RNAs in neurological conditions - computational identification, functional validation, and potential clinical applications

Non-coding RNAs (ncRNAs) have gained significant attention in recent years due to advancements in biotechnology, particularly high-throughput total RNA sequencing. These developments have led to new understandings of non-coding biology, revealing that approximately 80% of non-coding regions in the genome possesses biochemical functionality. Among ncRNAs, circular RNAs (circRNAs), first identified in 1976, have emerged as a prominent research field. CircRNAs are abundant in most human cell types, evolutionary conserved, highly stable, and formed by back-splicing events which generate covalently closed ends. Notably, circRNAs exhibit high expression levels in neural tissue and perform diverse biochemical functions, including acting as molecular sponges for microRNAs, interacting with RNA-binding proteins to regulate their availability and activity, modulating transcription and splicing, and even translating into functional peptides in some cases. Recent advancements in computational and experimental methods have enhanced our ability to identify and validate circRNAs, providing valuable insights into their biological roles. This review focuses on recent developments in circRNA research as they related to neuropsychiatric and neurodegenerative conditions. We also explore their potential applications in clinical diagnostics, therapeutics, and future research directions. CircRNAs remain a relatively underexplored area of non-coding biology, particularly in the context of neurological disorders. However, emerging evidence supports their role as critical players in the etiology and molecular mechanisms of conditions such as schizophrenia, bipolar disorder, major depressive disorder, Alzheimer's disease, and Parkinson's disease. These findings suggest that circRNAs may provide a novel framework contributing to the molecular dysfunctions underpinning these complex neurological conditions.

EIF4A3-Mediated Biogenesis of CircFADS1 Promotes the Progression of Hepatocellular Carcinoma via Wnt/β-Catenin Pathway

Mounting research indicates that circRNAs are pivotal elements in tumorigenesis and progression. Understanding the mechanisms by which circRNAs function in tumors is crucial for identifying undiscovered diagnostic and treatment targets. This research centers on unraveling the mechanisms by which the novel circRNA, circFADS1, influences hepatocellular carcinoma (HCC) progression. CircFADS1 shows elevated expression in HCC and is linked to unfavorable prognosis. Functionally, circFADS1 overexpression accelerates HCC progression through inducing HCC proliferation and inhibited apoptosis. Mechanistically, RNA-seq analysis demonstrates its connection to the Wnt/β-catenin pathway. Moreover, circFADS1 interacts with GSK3β and promotes its ubiquitination and degradation by recruiting the ubiquitin ligase RNF114 while EIF4A3 facilitates the biogenesis of circFADS1. Additionally, circFADS1 is closely linked to lenvatinib resistance. Overall, this study reveals that circFADS1 regulates GSK3β function, influencing the progression of hepatocellular carcinoma. The EIF4A3/circFADS1/GSK3β/β-catenin axis is discovered to hold promise as a novel therapeutic target for hepatocellular carcinoma, while circFADS1 is also a significant factor in lenvatinib resistance.

Unlocking the potential of circular RNA vaccines: a bioinformatics and computational biology perspective

Bioinformatics has significantly advanced RNA-based therapeutics, particularly circular RNAs (circRNAs), which outperform mRNA vaccines, by offering superior stability, sustained expression, and enhanced immunogenicity due to their covalently closed structure. This review highlights how bioinformatics and computational biology optimise circRNA vaccine design, elucidates internal ribosome entry sites (IRES) selection, open reading frame (ORF) optimisation, codon usage, RNA secondary structure prediction, and delivery system development. While circRNA vaccines may not always surpass traditional vaccines in stability, their production efficiency and therapeutic efficacy can be enhanced through computational strategies. The discussion also addresses challenges and future prospects, emphasizing the need for innovative solutions to overcome current limitations and advance circRNA vaccine applications.

Discovery of circular transcripts of the human BCL2-like 12 (BCL2L12) apoptosis-related gene, using targeted nanopore sequencing, provides new insights into circular RNA biology

Circular RNAs (circRNAs) constitute an RNA type formed by back-splicing. BCL2-like 12 (BCL2L12) is an apoptosis-related gene comprising 7 exons. In this study, we used targeted nanopore sequencing to identify circular BCL2L12 transcripts in human colorectal cancer cells and investigated the effect of circRNA silencing on mRNA expression of the parental gene. In brief, nanopore sequencing following nested PCR amplification of cDNAs of BCL2L12 circRNAs from 7 colorectal cancer cell lines unraveled 46 BCL2L12 circRNAs, most of which described for the first time. Interestingly, 40 novel circRNAs are likely to form via back-splicing between non-canonical back-splice sites residing in highly similar regions of the primary transcripts. All back-splice junctions were validated using next-generation sequencing (NGS) after circRNA enrichment. Surprisingly, 2 novel circRNAs also comprised a poly(A) tract after BCL2L12 exon 7; this poly(A) tract was back-spliced to exon 1, in both cases. Furthermore, the selective silencing of a BCL2L12 circRNA resulted in a subsequent decrease of BCL2L12 mRNA levels in HCT 116 cells, thus providing evidence of parental gene expression regulation by circRNAs. In conclusion, our study led to the discovery of many circular transcripts from a single human gene and provided new insights into circRNA biogenesis and mode of action.

A Novel Hidden Protein p-414aa Encoded by circSETD2(14,15) Inhibits Vascular Remodeling

BACKGROUND

Phenotypic switching of vascular smooth muscle cells (VSMCs), leading to neointimal hyperplasia, is a fundamental cause of vascular remodeling diseases such as atherosclerosis and hypertension. Novel hidden proteins encoded by circular RNAs play crucial roles in disease progression, yet their involvement in vascular remodeling diseases has not been comprehensively studied. This study identifies a novel protein derived from a circular RNA in VSMCs and demonstrates its potential role in regulating vascular remodeling.

METHODS

Cell proliferation assays were performed to investigate the effects of circSETD2(14,15) on VSMC proliferation. Techniques such as vector construction, immunoprecipitation-mass spectrometry, and dual-luciferase reporter gene were used to confirm that circSETD2(14,15) encoded a novel protein, p-414aa. The interaction between p-414aa and HuR (human antigen R) was validated with techniques such as coimmunoprecipitation, mass spectrometry, and proximity ligation assay. Through experiments including RNA sequencing and RNA immunoprecipitation, the interaction between HuR and C-FOS (C-Fos proto-oncogene) mRNA was revealed. The role of p-414aa in neointimal hyperplasia was assessed with a carotid artery ligation model in male mice.

RESULTS

Overexpression of circSETD2(14,15) inhibits VSMC phenotypic switching. The novel protein p-414aa, encoded by circSETD2(14,15), interacts with HuR to reduce C-FOS mRNA stability, thereby suppressing VSMC proliferation and ultimately inhibiting neointimal hyperplasia in male mice.

CONCLUSIONS

We uncover a novel hidden protein derived from circSETD2(14,15), called p-414aa, that inhibits vascular remodeling. CircSETD2(14,15) and p-414aa may serve as potential therapeutic targets for vascular remodeling diseases.

Predicting circRNA-Drug Resistance Associations Based on a Multimodal Graph Representation Learning Framework

Circular RNA (circRNA) is a class of noncoding RNA that is highly conserved and exhibit exceptional stability. Due to its function as a microRNA sponge, circRNA has gained significant attention as an essential biomarker and potential drug target in the pathogenesis of several cancers. Although many circRNAs have been identified to play a role in cancer resistance, traditional methods are time-consuming and expensive. In this context, computational methods offer a promising way to facilitate the discovery process. However, most existing prediction models focus on the association between circRNAs and drug resistance, without considering the corresponding disease-related information in the circRNA-drug resistance association. Incorporating disease-related information into the prediction of circRNA-drug resistance associations could potentially improve the efficiency and speed of discovering and developing circRNA-targeting drugs. We propose a computational framework, named GraphCDD, for predicting the association between circRNA and drug resistance. Our model utilizes data from three sources, namely circRNA, disease, and drug, to construct three similarity networks that represent the features of circRNA, disease, and drug, respectively. We utilize a multimodal graph neural network to acquire efficient representations of circRNAs, diseases, and drugs by integrating various types of information, and establish a predictive model. The experimental results have validated the effectiveness of our model and provided a promising method in predicting potential associations between circRNA and drug resistance.

Circular RNAs in cancer stem cells: Insights into their roles and mechanisms (Review)

Cancer stem cells (CSCs) represent a small, yet pivotal subpopulation of tumor cells that play significant roles in tumor initiation, progression and therapeutic resistance. Circular RNAs (circRNAs) are a distinct class of RNAs characterized by their closed‑loop structures, lacking 5' to 3'ends. There is growing evidence that circRNAs are integral to the development and regulation of CSCs. Aberrant expression of circRNAs in CSCs can contribute to oncogenic properties and drug resistance. Specifically, oncogenic circRNAs modulate CSC behavior via key signaling pathways, thereby promoting CSC self‑renewal and maintenance, as well as tumor progression. This review summarizes the latest research on the functional roles and regulatory mechanisms of circRNAs in CSC behavior and discusses potential applications and challenges of targeting circRNAs in CSCs. Understanding the intricate interactions between circRNAs and CSCs may lead to novel therapeutic strategies that effectively combat treatment resistance and improve patient outcomes.

Research progress of circular RNA FOXO3 in diseases (review)

Circular RNAs (circRNAs) are a newly discovered class of endogenous non-coding RNAs with a closed-loop structures, and they exert crucial regulatory functions in diverse biological processes and disease development through the modulation of linear RNA transcription, downstream gene expression, and protein translation, among others. Circular RNA FOXO3(circFOXO3, Hsa_circ_0006404) originates from exon 2 of the FOXO3 gene and exhibits widespread cytoplasmic expression in eukaryotic cells. It shows specific expression in different tissues or cells. Recent research has associated circFOXO3 with various diseases such as cancer, cardiovascular diseases, neurological disorders, senescence, and inflammation. However, a comprehensive review of the research progress of circFOXO3 in human diseases has not been conducted. In this paper, we provide a systematic review of the latest advances in circFOXO3 research in diseases, elucidate its biological functions and potential molecular mechanisms, and discuss the future directions and challenges in circRNAs research to provide valuable references and inspiration for research in this field.

Prostate Cancer: De-regulated Circular RNAs With Efficacy in Preclinical In Vivo Models

Therapy resistance, including castration-resistance and metastasis, remains a major hurdle in the treatment of prostate cancer. In order to identify novel therapeutic targets and treatment modalities for prostate cancer, we conducted a comprehensive literature search on PubMed to identify de-regulated circular RNAs that influence treatment efficacy in preclinical prostate cancer-related in vivo models. Our analysis identified 49 circular RNAs associated with various processes, including treatment resistance, transmembrane and secreted proteins, transcription factors, signaling cascades, human antigen R, nuclear receptor binding, ubiquitination, metabolism, epigenetics and other target categories. The identified targets and circular RNAs can be further scrutinized through target validation approaches. Down-regulated circular RNAs are candidates for reconstitution therapy, while up-regulated RNAs can be inhibited using small interfering RNA (siRNA), antisense oligonucleotides (ASO) or clustered regularly interspaced short palindromic repeats/CRISPR associated (CRISPR-CAS)-related approaches.

Species-specific circular RNA circDS-1 enhances adaptive evolution in Talaromyces marneffei through regulation of dimorphic transition

Thermal adaptability is a crucial characteristic for mammalian pathogenic fungi that originally inhabit natural ecosystems. Thermally dimorphic fungi have evolved a unique ability to respond to host body temperature by shifting from mycelia to yeast. The high similarity of protein-coding genes between these fungi and their relatives suggests the indispensable but often overlooked roles of non-coding elements in fungal thermal adaptation. Here, we systematically delineated the landscape of full-length circRNAs in both mycelial and yeast conditions of Talaromyces marneffei, a typical thermally dimorphic fungus causing fatal Talaromycosis, by optimizing an integrative pipeline for circRNA detection utilizing next- and third-generation sequencing. We found T. marneffei circRNA demonstrated features such as shorter length, lower abundance, and circularization-biased splicing. We then identified and validated that circDS-1, independent of its parental gene, promotes the hyphae-to-yeast transition, maintains yeast morphology, and is involved in virulence regulation. Further analysis and experiments among Talaromyces confirmed that the generation of circDS-1 is driven by a T. marneffei-specific region in the flanking intron of circDS-1. Together, our findings not only provide fresh insights into the role of circRNA in fungal thermal adaptation but also reveal a novel molecular mechanism for the adaptive evolution of functional circRNAs derived from intronic mutations.

Circular RNA CHACR is involved in the pathogenesis of cardiac hypertrophy

Background: Circular RNAs (circRNAs) exhibit differential expression in cardiac hypertrophy; however, their functions and mechanisms remain largely unexplored. This study aimed to determine the involvement of circRNAs in the pathogenesis of myocardial hypertrophy. Methods: A mouse model of cardiac hypertrophy was established using transverse aortic constriction (TAC) and differentially expressed circRNAs were identified via high-throughput sequencing. To facilitate gene overexpression or knockdown, related viruses were injected into myocardial tissues of the mice. Cardiomyocyte hypertrophy was assessed using quantitative real-time PCR and immunofluorescence staining. RNA immunoprecipitation, RNA pull-down assay and fluorescence in situ hybridization were conducted to confirm the interaction between circRNAs and proteins. Protein expression and degradation were evaluated using cycloheximide-chase assay, immunoprecipitation, and western blotting. Results: Cardiac hypertrophy-associated circRNA (CHACR) was significantly downregulated in myocardial tissues from TAC mice. CHACR can attenuate cardiac hypertrophy through upregulating carnitine palmitoyltransferase-1b (CPT1b) expression. Mechanistically, CHACR directly interacted with CPT1b and decreased its protein degradation by inhibiting the ubiquitin-proteasome pathway to increase its expression in cardiomyocytes. Moreover, CPT1b overexpression decreased L-carnitine levels and inhibited the Jak2/Stat3 signaling pathway, which was associated with the pathogenesis of myocardial hypertrophy. Conclusions: CHACR attenuated cardiomyocyte hypertrophy by facilitating the expression of CPT1b, which plays a role in regulating the Jak2/Stat3 pathway via L-carnitine. CHACR may thus be a potential therapeutic target for pathological myocardial hypertrophy.

m6A2Circ: A comprehensive database for decoding the regulatory relationship between m6A modification and circular RNA

Circular RNA (circRNA) is a class of noncoding RNAs derived from back-splicing of pre-mRNAs. Recent studies have increasingly highlighted the pivotal roles of N6-methyladenosine (m6A) in regulating various aspects of circRNA metabolism, including biogenesis, localization, stability, and translation. Despite the importance of m6A in circRNA metabolism, there remains a substantial gap in comprehensive resources dedicated to exploring m6A modification in circRNA. To bridge this significant gap, we present m6A2Circ (http://m6a2circ.canceromics.org/), a pioneering database designed to systematically explore the regulatory interactions between m6A modification and circRNA. The m6A2Circ database encompasses 198,804 m6A-circRNA associations derived from diverse human and mouse tissues. These associations are meticulously categorized into four levels of evidence supported either by experimental data or by high-throughput sequencing data. Moreover, the database offers extensive annotations, facilitating research into circRNA function and its potential disease implications. Overall, m6A2Circ aims to benefit the research community and bolster novel discoveries in terms of crosstalk between m6A and circRNA.

Identification of a circRNA-mediated immune-related ceRNA network and circRNAs as diagnostic biomarkers in acute ischemic stroke

BACKGROUND

Research has demonstrated that circular RNAs (circRNAs) play important roles in acute ischemic stroke (AIS). However, the functions of circRNA-mediated competitive endogenous RNA (ceRNA) in AIS-related immunological inflammation are not well understood. In our study, we aimed to construct a circRNA-mediated immune-related ceRNA network and identify diagnostic circRNAs for AIS.

METHODS

R software was used to analyze the microarray data obtained from the GEO database. The bioinformatics database was then used to develop the circRNA-mediated ceRNA network. A topological property study of the ceRNA network was performed to identify new circRNAs. Subsequently, we validated the potential circRNAs in both mice middle cerebral artery occlusion (MCAO) model and clinical samples obtained from our center with quantitative real-time polymerase chain reaction (qRT-PCR).

RESULTS

An AIS immune-related ceRNA (AISIRC) network was constructed, comprising immune-related genes (IRGs), circRNAs, and miRNAs. A subnetwork was then extracted from the AISIRC network and we identified seven circRNAs associated with immune response. The qRT-PCR assays were conducted to validate the circRNAs candidate using blood samples from MCAO mice. The results demonstrated that circulating circOXCT1 and circSLC8A1 were significantly up-regulated in AIS patients. Receiver-operating characteristic (ROC) curve analyses and logistic regression demonstrated the perfect predictive and discriminative features of these two circRNAs biomarkers in AIS. Longitudinal analysis of circRNA expression after AIS indicated the promising potential of circSLC8A1 for monitoring AIS progression and dynamics.

CONCLUSION

We successfully constructed circRNA-mediated immune-related ceRNA network and identified two circulating circRNAs (circOXCT1 and circSLC8A1), which showed high diagnostic sensitivity for AIS.

Circular RNA circASH1L(4,5) protects microRNA-129-5p from target-directed microRNA degradation in human skin wound healing

BACKGROUND

Skin wound healing involves a complex gene expression programme that remains largely undiscovered in humans. Circular RNAs (circRNAs) and microRNAs (miRNAs) are key players in this process.

OBJECTIVES

To understand the functions and potential interactions of circRNAs and miRNAs in human skin wound healing.

METHODS

CircRNA, linear RNA and miRNA expression in human acute and chronic wounds were analysed with RNA sequencing and quantitative reverse transcription polymerase chain reaction. The roles of circASH1L(4,5) and miR-129-5p were studied in human primary keratinocytes (proliferation and migration assays, microarray analysis) and ex vivo wound models (histological analysis). The interaction between circASH1L(4,5) and miR-129-5p was examined using luciferase reporter and RNA pulldown assays.

RESULTS

We identified circASH1L(4,5) and its interaction with miR-129-5p, both of which increased during human skin wound healing. Unlike typical miRNA sponging, circASH1L enhanced miR-129 stability and silencing activity by protecting it from target-directed degradation triggered by NR6A1 mRNA. Transforming growth factor-β signalling - crucial in wound healing - promoted circASH1L expression while suppressing NR6A1, thereby increasing the abundance of miR-129 at the post-transcriptional level. CircASH1L and miR-129 enhanced keratinocyte migration and proliferation, crucial processes for the re-epithelialization of human wounds.

CONCLUSIONS

Our study uncovered a novel role for circRNAs as protectors of miRNAs and highlights the importance of regulated miRNA degradation in skin wound healing.

Identification of a functional CircRNA-miRNA-mRNA network and inhibitory effect of Hsa_circ_0001681 on gliomas

OBJECTIVE

Gliomas pose a significant global health challenge due to high rates of morbidity and mortality. Recent research has indicated that circular RNAs (circRNAs) may play a crucial role in gliomas. However, the specific impacts of circRNAs on gliomas development is poorly understood. Therefore, the present study aimed to explore the roles of circRNAs in gliomas by analyzing their interactions with microRNAs (miRNAs) and messenger RNAs (mRNAs).

METHODS

Datasets were extracted from the Gene Expression Omnibus (GEO) database to investigate differentially expressed circRNAs in gliomas. Using the Circular RNA Interactome, we predicted interactions between the identified circRNAs and 125 target miRNAs, focusing on 15 key miRNAs selected by intersection analysis. The miRNet database was applied to predict 2635 target mRNAs, constructing a comprehensive circRNA-miRNA-mRNA network, while functional enrichment analyses were conducted to determine the roles of this network.

RESULTS

Four circRNAs with significant differential expression in glioma samples were identified. The constructed network indicated the substantial involvement of transcriptional regulation and cancer-related pathways. Notably, hsa_circ_0001681 was highlighted as a key circRNA, which was further validated through Sanger sequencing and quantitative reverse transcription PCR (qRT-PCR). Functional assays, including cellular assays and animal xenograft experiments, demonstrated that hsa_circ_0001681 inhibits glioma carcinogenesis in vitro and in vivo.

CONCLUSION

Our investigation highlights the significant role of the circRNA-miRNA-mRNA network in the pathophysiology of gliomas, and supports the potential of hsa_circ_0001681 as a diagnostic and therapeutic biomarker. These findings present new opportunities for understanding the molecular mechanisms underlying glioma and developing targeted treatments.

The mechanisms of Chr.9p21.3 risk locus in coronary artery disease: where are we today?

Despite the advancements and release of new therapeutics in the past few years, cardiovascular diseases (CVDs) have remained the number one cause of death worldwide. Genetic variation of a 9p21.3 genomic locus has been identified as the most significant and robust genetic CVD risk marker on the population level, with the strongest association with coronary artery disease (CAD) and other diseases, including diabetes and cancer. Several mechanisms of 9p21.3 in CVDs have been proposed, but their effects on CVDs have remained elusive. Moreover, most of the single nucleotide polymorphisms (SNPs) associated with CAD are located on a sequence of a long noncoding RNA (lncRNA) called ANRIL. ANRIL has several linear and circular splicing isoforms, which seem to have different effects and implications for CVDs. The mechanisms of the 9p21.3 locus and the interplay of its coding and noncoding transcripts in different diseases require further research. Circular RNAs have generally raised interest due to their beneficial features as biomarkers and therapeutic molecules. Here, we review the literature of 9p21.3 from its identification in 2007 and draw the current knowledge on its function, implications in CVDs, and therapeutic potential.

CellCircLoc: Deep Neural Network for Predicting and Explaining Cell Line-Specific CircRNA Subcellular Localization

The subcellular localization of circular RNAs (circRNAs) is crucial for understanding their functional relevance and regulatory mechanisms. CircRNA subcellular localization exhibits variations across different cell lines, demonstrating the diversity and complexity of circRNA regulation within distinct cellular contexts. However, existing computational methods for predicting circRNA subcellular localization often ignore the importance of cell line specificity and instead train a general model on aggregated data from all cell lines. Considering the diversity and context-dependent behavior of circRNAs across different cell lines, it is imperative to develop cell line-specific models to accurately predict circRNA subcellular localization. In the study, we proposed CellCircLoc, a sequence-based deep learning model for circRNA subcellular localization prediction, which is trained for different cell lines. CellCircLoc utilizes a combination of convolutional neural networks, Transformer blocks, and bidirectional long short-term memory to capture both sequence local features and long-range dependencies within the sequences. In the Transformer blocks, CellCircLoc uses an attentive convolution mechanism to capture the importance of individual nucleotides. Extensive experiments demonstrate the effectiveness of CellCircLoc in accurately predicting circRNA subcellular localization across different cell lines, outperforming other computational models that do not consider cell line specificity. Moreover, the interpretability of CellCircLoc facilitates the discovery of important motifs associated with circRNA subcellular localization.

Hsa_circ_0001304 promotes vascular neointimal hyperplasia accompanied by autophagy activation

Aberrant autophagy in vascular smooth muscle cells (VSMCs) is associated with the progression of vascular remodeling diseases caused by neointimal hyperplasia. Platelet-derived growth factor-BB (PDGF-BB)-induced vascular remodeling is accompanied by autophagy activation, however, the involvement of circular RNAs (circRNAs) remains unclear. Here, we show the role of PDGF-BB-regulated hsa_circ_0001304 (circ-1304) in neointimal hyperplasia and its potential involvement in VSMC autophagy, while also elucidating the potential mechanisms. Functionally, overexpression of circ-1304 promotes VSMC autophagy in vitro and exacerbates neointimal hyperplasia in vivo, and this exacerbation is accompanied by autophagy activation. Mechanistically, circ-1304 acts as a sponge for miR-636, resulting in increased protein levels of YTHDF2. Subsequently, the YTHDF2 protein promotes the degradation of mTOR mRNA by binding to the latter's m6A modification sites. We demonstrate that PDGF-BB activates VSMC autophagy via circRNA regulation. Therefore, circ-1304 may serve as a potential therapeutic target for vascular remodeling diseases.

Unlocking the secrets of the immunopeptidome: MHC molecules, ncRNA peptides, and vesicles in immune response

The immunopeptidome, a diverse set of peptides presented by Major Histocompatibility Complex (MHC) molecules, is a critical component of immune recognition and response. This review article delves into the mechanisms of peptide presentation by MHC molecules, particularly emphasizing the roles of ncRNA-derived peptides and extracellular vesicles (EVs) in shaping the immunopeptidome landscape. We explore established and emerging insights into MHC molecule interactions with peptides, including the dynamics of peptide loading, transport, and the influence of cellular and genetic variations. The article highlights novel research on non-coding RNA (ncRNA)-derived peptides, which challenge conventional views of antigen processing and presentation and the role of EVs in transporting these peptides, thereby modulating immune responses at remote body sites. This novel research not only challenges conventional views but also opens up new avenues for understanding immune responses. Furthermore, we discuss the implications of these mechanisms in developing therapeutic strategies, particularly for cancer immunotherapy. By conducting a comprehensive analysis of current literature and advanced methodologies in immunopeptidomics, this review aims to deepen the understanding of the complex interplay between MHC peptide presentation and the immune system, offering new perspectives on potential diagnostic and therapeutic applications. Additionally, the interactions between ncRNA-derived peptides and EVs provide a mechanism for the enhanced surface presentation of these peptides and highlight a novel pathway for their systemic distribution, potentially altering immune surveillance and therapeutic landscapes.

Research progress of circRNAs in bone-related diseases

Circular RNAs (circRNAs) are non-coding RNAs that exist naturally in various eukaryotic organisms. The majority of circRNAs are produced through the splicing of exons, although there are a limited number that are generated through the circularization of introns. Studies have shown that circRNAs play an irreplaceable role in the pathogenesis, disease progression, diagnosis, and targeted therapy of motor system tumors (osteosarcoma), metabolic diseases (osteoporosis), and degenerative diseases (osteonecrosis of the femoral head, osteoarthritis, intervertebral disc degeneration). This review summarizes the advancements in circRNA detection techniques and the research progress of circRNAs in orthopedic diseases.

Full-length nanopore sequencing of circular RNA landscape in peripheral blood cells following sequential BNT162b2 mRNA vaccination

Circular RNAs (circRNA) lack 5' or 3' ends; their unique covalently closed structures prevent RNA degradation by exonucleases. These characteristics provide circRNAs with high pharmaceutical stability and biostability relative to current standard-of-care linear mRNAs. CircRNA levels are reportedly associated with certain human diseases, making them novel disease biomarkers and a noncanonical class of therapeutic targets. In this study, the endogenous circRNAs underlying the response to BNT162b2 mRNA vaccination were evaluated. To this end, peripheral blood samples were subjected to full-length sequencing of circRNAs via nanopore sequencing and transcriptome sequencing. Fifteen samples, comprising pre-, first, and second vaccination cohorts, were obtained from five healthcare workers with no history of SARS-CoV-2 infection or previous vaccination. A total of 4706 circRNAs were detected; following full-length sequencing, 4217 novel circRNAs were identified as being specifically expressed during vaccination. These circRNAs were enriched in the binding motifs of stress granule assemblies and SARS-CoV-2 RNA binding proteins, namely poly(A) binding protein cytoplasmic 1 (PABPC1), pumilio RNA binding family member 1 (PUM1), and Y box binding protein 1 (YBX1). Moreover, 489 circRNAs were identified as previously reported miRNA sponges. The differentially expressed circRNAs putatively originated from plasma B cells compared to circRNAs reported in human blood single-cell RNA sequencing datasets. The pre- and post-vaccination differences observed in the circRNA expression landscape in response to the SARS-CoV-2 BNT162b2 mRNA vaccine.

Recent advances in investigation of circRNA/lncRNA-miRNA-mRNA networks through RNA sequencing data analysis

Non-coding RNAs (ncRNAs) are RNA molecules that are transcribed from DNA but are not translated into proteins. Studies over the past decades have revealed that ncRNAs can be classified into small RNAs, long non-coding RNAs and circular RNAs by genomic size and structure. Accumulated evidences have eludicated the critical roles of these non-coding transcripts in regulating gene expression through transcription and translation, thereby shaping cellular function and disease pathogenesis. Notably, recent studies have investigated the function of ncRNAs as competitive endogenous RNAs (ceRNAs) that sequester miRNAs and modulate mRNAs expression. The ceRNAs network emerges as a pivotal regulatory function, with significant implications in various diseases such as cancer and neurodegenerative disease. Therefore, we highlighted multiple bioinformatics tools and databases that aim to predict ceRNAs interaction. Furthermore, we discussed limitations of using current technologies and potential improvement for ceRNAs network detection. Understanding of the dynamic interplay within ceRNAs may advance the biological comprehension, as well as providing potential targets for therapeutic intervention.

RNALocate v3.0: Advancing the Repository of RNA Subcellular Localization with Dynamic Analysis and Prediction

Subcellular localization of RNA is a crucial mechanism for regulating diverse biological processes within cells. Dynamic RNA subcellular localizations are essential for maintaining cellular homeostasis; however, their distribution and changes during development and differentiation remain largely unexplored. To elucidate the dynamic patterns of RNA distribution within cells, we have upgraded RNALocate to version 3.0, a repository for RNA-subcellular localization (http://www.rnalocate.org/ or http://www.rna-society.org/rnalocate/). RNALocate v3.0 incorporates and analyzes RNA subcellular localization sequencing data from over 850 samples, with a specific focus on the dynamic changes in subcellular localizations under various conditions. The species coverage has also been expanded to encompass mammals, non-mammals, plants and microbes. Additionally, we provide an integrated prediction algorithm for the subcellular localization of seven RNA types across eleven subcellular compartments, utilizing convolutional neural networks (CNNs) and transformer models. Overall, RNALocate v3.0 contains a total of 1 844 013 RNA-localization entries covering 26 RNA types, 242 species and 177 subcellular localizations. It serves as a comprehensive and readily accessible data resource for RNA-subcellular localization, facilitating the elucidation of cellular function and disease pathogenesis.

RMVar 2.0: an updated database of functional variants in RNA modifications

Evaluating the impact of genetic variants on RNA modifications (RMs) is crucial for identifying disease-associated variants and understanding the pathogenic mechanisms underlying human diseases. Previously, we developed a database called RMVar to catalog variants linked to RNA modifications in humans and mice. Here, we present an updated version RMVar 2.0 (http://rmvar.renlab.cn). In this updated version, we applied an enhanced analytical pipeline to the latest RNA modification datasets and genetic variant information to identify RM-associated variants. A notable advancement in RMVar 2.0 is our incorporation of allele-specific RNA modification analysis to identify RM-associated variants, a novel approach not utilized in RMVar 1.0 or other comparable databases. Furthermore, the database offers comprehensive annotations for various molecular events, including RNA-binding protein (RBP) interactions, RNA-RNA interactions, splicing events, and circular RNAs (circRNAs), which facilitate investigations into how RM-associated variants influence post-transcriptional regulation. Additionally, we provide disease-related information sourced from ClinVar and GWAS to help researchers explore the connections between RNA modifications and various diseases. We believe that RMVar 2.0 will significantly enhance our understanding of the functional implications of genetic variants affecting RNA modifications within the context of human disease research.

PlantCircRNA: a comprehensive database for plant circular RNAs

Circular RNAs (circRNAs) represent recently discovered novel regulatory non-coding RNAs. While they are present in many eukaryotes, there has been limited research on plant circRNAs. We developed PlantCircRNA (https://plant.deepbiology.cn/PlantCircRNA/) to fill this gap. The two most important features of PlantCircRNA are (i) it incorporates circRNAs from 94 plant species based on 39 245 RNA-sequencing samples and (ii) it imports the original AtCircDB and CropCircDB databases. We manually curated all circRNAs from published articles, and imported them into the database. Furthermore, we added detailed information of tissue as well as abiotic stresses to the database. To help users understand these circRNAs, the database includes a detection score to measure their consistency and a naming system following the guidelines recently proposed for eukaryotes. Finally, we developed a comprehensive platform for users to visualize, analyze, and download data regarding specific circRNAs. This resource will serve as a home for plant circRNAs and provide the community with unprecedented insights into these mysterious molecule.

Transcriptomic profiling and machine learning reveal novel RNA signatures for enhanced molecular characterization of Hashimoto's thyroiditis

While ultrasonography effectively diagnoses Hashimoto's thyroiditis (HT), exploring its transcriptomic landscape could reveal valuable insights into disease mechanisms. This study aimed to identify HT-associated RNA signatures and investigate their potential for enhanced molecular characterization. Samples comprising 31 HT patients and 30 healthy controls underwent RNA sequencing of peripheral blood. Differential expression analysis identified transcriptomic features, which were integrated using multi-omics factor analysis. Pathway enrichment, co-expression, and regulatory network analyses were performed. A novel machine-learning model was developed for HT molecular characterization using stacking techniques. HT patients exhibited increased thyroid volume, elevated tissue hardness, and higher antibody levels despite being in the early subclinical stage. Analysis identified 79 HT-associated transcriptomic features (3 mRNA, 6 miRNA, 64 lncRNA, 6 circRNA). Co-expression (77 nodes, 266 edges) and regulatory (18 nodes, 45 edges) networks revealed significant hub genes and modules associated with HT. Enrichment analysis highlighted dysregulation in immune system, cell adhesion and migration, and RNA/protein regulation pathways. The novel stacking-model achieved 95% accuracy and 97% AUC for HT molecular characterization. This study demonstrates the value of transcriptome analysis in uncovering HT-associated signatures, providing insights into molecular changes and potentially guiding future research on disease mechanisms and therapeutic strategies.

Silencing circLDLRAD3 Inhibits Lung Cancer Progression by Regulating the miR-497-5p/PFKP Axis

PURPOSE

Lung cancer is one of the leading causes of death worldwide. Recent studies have shown that circular RNAs are dysregulated in a variety of cancers, but the mechanism in lung cancer is still indistinct. In our work, we explored the action mechanism of circLDLRAD3 in lung cancer.

METHODS

The abundance of circLDLRAD3, microRNA-497-5p (miR-497-5p) and platelet-type PFK (PFKP) was measured by real-time quantitative polymerase chain reaction (RT-qPCR) in lung cancer. Meanwhile, the level of PFKP was quantified by western blot. Cell counting kit-8 (CCK-8), 5-Ethynyl-2'-deoxyuridine (EdU) assay, transwell assay, wound healing assay, flow cytometry, western blot, immunohistochemical (IHC) assay and glycolysis metabolism analysis were performed for functional analyses. Furthermore, the interplay between miR-497-5p and circLDLRAD3 or FKPF was detected by the dual-luciferase reporter and RNA Immunoprecipitation (RIP) assays. Eventually, the in vivo experiments were applied to measure the role of circLDLRAD3.

RESULT

The levels of circLDLRAD3 and PFKP were increased. Silencing circLDLRAD3 inhibited cell viability, proliferation, migration, invasion and glycolysis metabolism and promoted cell apoptosis in lung cancer cells. In mechanism, circLDLRAD3 regulated PFKP level as a miR-497-5p sponge. MiR-497-5p suppressed the progression of lung cancer by inhibiting PFKP. In addition, circLDLRAD3 knockdown also inhibited tumor growth in vivo.

CONCLUSION

CircLDLRAD3 promoted the development of lung cancer through increasing PFKP expression by regulating miR-497-5p, which also provided a potential targeted therapy for lung cancer treatment.

Expression and Significance of the Circular RNA circ_0001438 in the Development of Gastric Cancer

Gastric cancer has become a great challenge to human health in the world. We studied the expression and role of the circular RNA 0001438 (circ_0001438) with the aim of finding a biomarker to assess the prognosis of gastric cancer. Through a polymerase chain reaction, circ_0001438 expression in gastric cancer was detected. Chi-square test, multi-factor Cox regression, and Kaplan-Meier analyses were used to determine the association between circ_0001438 and the patients' clinical condition and prognosis. Using the luciferase reporter gene system, the interaction between circ_0001438 and miR-1290 was analyzed, and the regulatory impact of circ_0001438/miR-1290 on the activity of gastric cancer cells was examined flowing the Transwell assay and CCK8 assay. In gastric cancer tissues and cells, circ_0001438 expression was downregulated, and miR-1290 expression was upregulated and the two were negatively correlated. miR-1290 inhibitors were transfected and significantly increased the activity of circ_0001438 luciferase, while miR-1290 mimics decreased the activity. Overexpression of circ_0001438 decreased miR-1290 expression and inhibited the proliferation and metastasis of gastric cancer cells, which was reversed when miR-1290 mimics were transfected. Additionally, there was a correlation between circ_0001438 expression and lymph node metastases, tumor size, and TNM stage of gastric cancer. Low circ_0001438 expression predicts poor prognosis of gastric cancer patients. circ_0001438 is a biomarker for tumor development and clinical prognosis in gastric cancer. It works by downregulating miR-1290 to control the activity of gastric cancer cells.

Role of Circular RNA MMP9 in Glioblastoma Progression: From Interaction With hnRNPC and hnRNPA1 to Affecting the Expression of BIRC5 by Sequestering miR-149

Glioblastoma multiforme (GBM) presents a significant challenge in neuro-oncology due to its aggressive behavior and self-renewal capacity. Circular RNAs (circRNAs), a subset of non-coding RNAs (ncRNAs) generated through mRNA back-splicing, are gaining attention as potential targets for GBM research. In our study, we sought to explore the functional role of circMMP9 (circular form of matrix metalloproteinase-9) as a promising therapeutic target for GBM through bioinformatic predictions and human data analysis. Our results suggest that circMMP9 functions as a sponge for miR-149 and miR-542, both upregulated in GBM based on microarray data. Kaplan-Meier analysis indicated that reduced levels of miR-149 and miR-542 correlate with worse survival outcomes in GBM, suggesting their role as tumor suppressors. Importantly, miR-149 has been demonstrated to inhibit the expression of BIRC5 (baculoviral inhibitor of apoptosis repeat-containing 5 or survivin), a significant promoter of proliferation in GBM. BIRC5 is not only upregulated in GBM but also in various other cancers, including neuroblastoma and other brain cancers. Our protein-protein interaction analysis highlights the significance of BIRC5 as a central hub gene in GBM. CircMMP9 seems to influence this complex relationship by suppressing miR-149 and miR-542, despite their increased expression in GBM. Additionally, we found that circMMP9 directly interacts with heterogeneous nuclear ribonucleoproteins C and A1 (hnRNPC and A1), although not within their protein-binding domains. This suggests that hnRNPC/A1 may play a role in transporting circMMP9. Moreover, RNA-seq data from GBM patient samples confirmed the increased expression of BIRC5, PIK3CB, and hnRNPC/A1, further emphasizing the potential therapeutic significance of circMMP9 in GBM. In this study, we propose for the first time a new epigenetic regulatory role for circMMP9, highlighting a novel aspect of its oncogenic function. circMMP9 may regulate BIRC5 expression in GBM by sponging miR-149 and miR-542. BIRC5, in turn, suppresses apoptosis and enhances proliferation in GBM. Nonetheless, more extensive studies are advised to delve deeper into the roles of circMMP9, especially in the context of glioma.