CELF1 contributes to aberrant alternative splicing patterns in the type 1 diabetic heart

circGlis3 promotes β-cell dysfunction by binding to heterogeneous nuclear ribonucleoprotein F and encoding Glis3-348aa protein

Circular RNAs (circRNAs) are crucial regulators of β-cell function and are involved in lipotoxicity-induced β-cell damage in type 2 diabetes mellitus (T2DM). We previously identified that circGlis3, a circRNA derived from exon 4 of the diabetes susceptibility gene Glis3, was upregulated in lipotoxic β cells. However, the functional role and molecular mechanism of circGlis3 in β cells remain largely unknown. Here, we revealed that the splicing factor CUGBP Elav-Like Family Member 1 (CELF1) facilitated the biogenesis of circGlis3. Moreover, we established a transgenic mouse model and confirmed that the overexpression of circGlis3 impaired β-cell function. Mechanistically, circGlis3 bound to heterogeneous nuclear ribonucleoprotein F (hnRNPF) and blocked its nuclear translocation, thereby reducing Sirt1 levels. Additionally, circGlis3 encoded a 348aa protein that interacted with GLIS3 and inhibited its transcriptional activity. Our data uncover a critical role of circGlis3 in β-cell dysfunction, suggesting that circGlis3 may be a potential therapeutic target for T2DM.

CELF1 Selectively Regulates Alternative Splicing of DNA Repair Genes Associated With Cataract in Human Lens Cell Line

Cataract is a global eye disease caused by the opacification of lens, while its underlying molecular pathogenesis is not clear, making it difficult for prevention. CELF1, an RNA binding protein, mediates Alternative Splicing (AS) of genes involved in diverse diseases and regulates development or defects of lens. Utilizing transcriptome-wide approaches, we analyzed and compared AS patterns between human lens epithelial cells (SRA01/04) with CELF1 overexpression (CELF1-OE) and control cells. Extensive changes in AS patterns upon CELF1-OE were identified in SRA01/04 cells. We finally identified 840 CELF1-regulated AS events (RASEs) and found that CELF1-OE preferred to repress exon skipping events in SRA01/04 cells. CELF1-regulated AS genes were enriched in the regulation of DNA repair, cellular response to DNA damage stimulus, and apoptosis pathways (including HMGA2, CSNK1E, and YAP1). These biological functions and pathways have been reported to be associated with lens development or other eye diseases. To further explore the mechanisms of CELF1 in regulating AS genes, we downloaded and re-analyzed a set of CELF1-RNA interactome data. We found that 194 genes were bound and regulated by CELF1 at the AS level. 10 genes involved in DNA repair-related pathways were also bound by CELF1. Motif analysis for CELF1-bound peaks and splicing sites of RASEs showed that CELF1 regulates AS by binding to the AGGU[AG]AG motif in SRA01/04 cells. CELF1 could mediate AS of DNA repair-related genes through directly binding to their transcripts with distinct motif bias. The functional mechanism of CELF1 may ultimately participate in cataract formation and lens development.

Post-transcriptional control by RNA-binding proteins in diabetes and its related complications

Diabetes mellitus (DM) is a fast-growing chronic metabolic disorder that leads to significant health, social, and economic problems worldwide. Chronic hyperglycemia caused by DM leads to multiple devastating complications, including macrovascular complications and microvascular complications, such as diabetic cardiovascular disease, diabetic nephropathy, diabetic neuropathy, and diabetic retinopathy. Numerous studies provide growing evidence that aberrant expression of and mutations in RNA-binding proteins (RBPs) genes are linked to the pathogenesis of diabetes and associated complications. RBPs are involved in RNA processing and metabolism by directing a variety of post-transcriptional events, such as alternative splicing, stability, localization, and translation, all of which have a significant impact on RNA fate, altering their function. Here, we purposed to summarize the current progression and underlying regulatory mechanisms of RBPs in the progression of diabetes and its complications. We expected that this review will open the door for RBPs and their RNA networks as novel therapeutic targets for diabetes and its related complications.

Alternative Splicing of the Aryl Hydrocarbon Receptor Nuclear Translocator (ARNT) Is Regulated by RBFOX2 in Lymphoid Malignancies

Aberrant alternative splicing (AS) of pre-mRNAs promotes the development and proliferation of cancerous cells. Accordingly, we had previously observed higher levels of the aryl hydrocarbon receptor nuclear translocator (ARNT) spliced variant isoform 1 in human lymphoid malignancies compared to that in normal lymphoid cells, which is a consequence of increased inclusion of alternative exon 5. ARNT is a transcription factor that has been implicated in the survival of various cancers. Notably, we found that ARNT isoform 1 promoted the growth and survival of lymphoid malignancies, but the regulatory mechanism controlling ARNT AS is unclear. Here, we report cis- and trans-regulatory elements which are important for the inclusion of ARNT exon 5. Specifically, we identified recognition motifs for the RNA-binding protein RBFOX2, which are required for RBFOX2-mediated exon 5 inclusion. RBFOX2 upregulation was observed in lymphoid malignancies, correlating with the observed increase in ARNT exon 5 inclusion. Moreover, suppression of RBFOX2 significantly reduced ARNT isoform 1 levels and cell growth. These observations reveal RBFOX2 as a critical regulator of ARNT AS in lymphoid malignancies and suggest that blocking the ARNT-specific RBFOX2 motifs to decrease ARNT isoform 1 levels is a viable option for targeting the growth of lymphoid malignancies.

Advances in The Study of RNA-binding Proteins in Diabetic Complications

Background

It has been reported that diabetes mellitus affects 435 million people globally as a primary health care problem. Despite many therapies available, many diabetes remains uncontrolled, giving rise to irreversible diabetic complications that pose significant risks to patients’ wellbeing and survival.

Scope of Review

In recent years, as much effort is put into elucidating the posttranscriptional gene regulation network of diabetes and diabetic complications; RNA binding proteins (RBPs) are found to be vital. RBPs regulate gene expression through various post-transcriptional mechanisms, including alternative splicing, RNA export, messenger RNA translation, RNA degradation, and RNA stabilization.

Major Conclusions

Here, we summarized recent studies on the roles and mechanisms of RBPs in mediating abnormal gene expression in diabetes and its complications. Moreover, we discussed the potential and theoretical basis of RBPs to treat diabetes and its complications.

• Mechanisms of action of RBPs involved in diabetic complications are summarized and elucidated.

• We discuss the theoretical basis and potential of RBPs for the treatment of diabetes and its complications.

• We summarize the possible effective drugs for diabetes based on RBPs promoting the development of future therapeutic drugs.

CELF1 promotes matrix metalloproteinases gene expression at transcriptional level in lens epithelial cells

Background

RNA binding proteins (RBPs)-mediated regulation plays important roles in many eye diseases, including the canonical RBP CELF1 in cataract. While the definite molecular regulatory mechanisms of CELF1 on cataract still remain elusive.

Methods

In this study, we overexpressed CELF1 in human cultured lens epithelial SRA01/04 cells and applied whole transcriptome sequencing (RNA-seq) method to analyze the global differences mediated by CELF1. We then analyzed public RNA-seq and CELF1-RNA interactome data to decipher the underlying mechanisms.

Results

The results showed that transcriptome profile was globally changed by CELF1 overexpression (CELF1-OE). Functional analysis revealed CELF1 specifically increased the expression of genes in extracellular matrix disassembly, extracellular matrix organization, and proteolysis, which could be classified into matrix metalloproteinases (MMPs) family. This finding was also validated by RT-qPCR and public mouse early embryonic lens data. Integrating analysis with public CELF1-RNA interactome data revealed that no obvious CELF1-binding peak was found on the transcripts of these genes, indicating an indirectly regulatory role of CELF1 in lens epithelial cells.

Conclusions

Our study demonstrated that CELF1-OE promotes transcriptional level of MMP genes; and this regulation may be completed by other ways except for binding to RNA targets. These results suggest that CELF1-OE is implicated in the development of lens, which is associated with cataract and expands our understanding of CELF1 regulatory roles as an RNA binding protein.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12886-022-02344-8.

RBFOX2 is critical for maintaining alternative polyadenylation patterns and mitochondrial health in rat myoblasts

RBFOX2, which has a well-established role in alternative splicing, is linked to heart diseases. However, it is unclear whether RBFOX2 has other roles in RNA processing that can influence gene expression in muscle cells, contributing to heart disease. Here, we employ both 3'-end and nanopore cDNA sequencing to reveal a previously unrecognized role for RBFOX2 in maintaining alternative polyadenylation (APA) signatures in myoblasts. RBFOX2-mediated APA modulates mRNA levels and/or isoform expression of a collection of genes, including contractile and mitochondrial genes. Depletion of RBFOX2 adversely affects mitochondrial health in myoblasts, correlating with disrupted APA of mitochondrial gene Slc25a4. Mechanistically, RBFOX2 regulation of Slc25a4 APA is mediated through consensus RBFOX2 binding motifs near the distal polyadenylation site, enforcing the use of the proximal polyadenylation site. In sum, our results unveil a role for RBFOX2 in fine-tuning expression of mitochondrial and contractile genes via APA in myoblasts relevant to heart diseases.

Association Study among Comethylation Modules, Genetic Polymorphisms and Clinical Features in Mexican Teenagers with Eating Disorders: Preliminary Results

Eating disorders are psychiatric disorders characterized by disturbed eating behaviors. They have a complex etiology in which genetic and environmental factors interact. Analyzing gene-environment interactions could help us to identify the mechanisms involved in the etiology of such conditions. For example, comethylation module analysis could detect the small effects of epigenetic interactions, reflecting the influence of environmental factors. We used MethylationEPIC and Psycharray microarrays to determine DNA methylation levels and genotype from 63 teenagers with eating disorders. We identified 11 comethylation modules in WGCNA (Weighted Gene Correlation Network Analysis) and correlated them with single nucleotide polymorphisms (SNP) and clinical features in our subjects. Two comethylation modules correlated with clinical features (BMI and height) in our sample and with SNPs associated with these phenotypes. One of these comethylation modules (yellow) correlated with BMI and rs10494217 polymorphism (associated with waist-hip ratio). Another module (black) was correlated with height, rs9349206, rs11761528, and rs17726787 SNPs; these polymorphisms were associated with height in previous GWAS. Our data suggest that genetic variations could alter epigenetics, and that these perturbations could be reflected as variations in clinical features.

RBPTD: a database of cancer-related RNA-binding proteins in humans

RNA-binding proteins (RBPs) play important roles in regulating the expression of genes involved in human physiological and pathological processes, especially in cancers. Many RBPs have been found to be dysregulated in cancers; however, there was no tool to incorporate high-throughput data from different dimensions to systematically identify cancer-related RBPs and to explore their causes of abnormality and their potential functions. Therefore, we developed a database named RBPTD to identify cancer-related RBPs in humans and systematically explore their functions and abnormalities by integrating different types of data, including gene expression profiles, prognosis data and DNA copy number variation (CNV), among 28 cancers. We found a total of 454 significantly differentially expressed RBPs, 1970 RBPs with significant prognostic value, and 53 dysregulated RBPs correlated with CNV abnormality. Functions of 26 cancer-related RBPs were explored by analysing high-throughput RNA sequencing data obtained by crosslinking immunoprecipitation, and the remaining RBP functions were predicted by calculating their correlation coefficient with other genes. Finally, we developed the RBPTD for users to explore functions and abnormalities of cancer-related RBPs to improve our understanding of their roles in tumorigenesis.

Database URL: http: //www.rbptd.com

Integrated analysis of a compendium of RNA-Seq datasets for splicing factors

A vast amount of public RNA-sequencing datasets have been generated and used widely to study transcriptome mechanisms. These data offer precious opportunity for advancing biological research in transcriptome studies such as alternative splicing. We report the first large-scale integrated analysis of RNA-Seq data of splicing factors for systematically identifying key factors in diseases and biological processes. We analyzed 1,321 RNA-Seq libraries of various mouse tissues and cell lines, comprising more than 6.6 TB sequences from 75 independent studies that experimentally manipulated 56 splicing factors. Using these data, RNA splicing signatures and gene expression signatures were computed, and signature comparison analysis identified a list of key splicing factors in Rett syndrome and cold-induced thermogenesis. We show that cold-induced RNA-binding proteins rescue the neurite outgrowth defects in Rett syndrome using neuronal morphology analysis, and we also reveal that SRSF1 and PTBP1 are required for energy expenditure in adipocytes using metabolic flux analysis. Our study provides an integrated analysis for identifying key factors in diseases and biological processes and highlights the importance of public data resources for identifying hypotheses for experimental testing.

miRDRN-miRNA disease regulatory network: a tool for exploring disease and tissue-specific microRNA regulatory networks

BACKGROUND

MicroRNA (miRNA) regulates cellular processes by acting on specific target genes, and cellular processes proceed through multiple interactions often organized into pathways among genes and gene products. Hundreds of miRNAs and their target genes have been identified, as are many miRNA-disease associations. These, together with huge amounts of data on gene annotation, biological pathways, and protein-protein interactions are available in public databases. Here, using such data we built a database and web service platform, miRNA disease regulatory network (miRDRN), for users to construct disease and tissue-specific miRNA-protein regulatory networks, with which they may explore disease related molecular and pathway associations, or find new ones, and possibly discover new modes of drug action.

METHODS

Data on disease-miRNA association, miRNA-target association and validation, gene-tissue association, gene-tumor association, biological pathways, human protein interaction, gene ID, gene ontology, gene annotation, and product were collected from publicly available databases and integrated. A large set of miRNA target-specific regulatory sub-pathways (RSPs) having the form (T, G 1, G 2) was built from the integrated data and stored, where T is a miRNA-associated target gene, G 1 (G 2) is a gene/protein interacting with T (G 1). Each sequence (T, G 1, G 2) was assigned a p-value weighted by the participation of the three genes in molecular interactions and reaction pathways.

RESULTS

A web service platform, miRDRN (http://mirdrn.ncu.edu.tw/mirdrn/), was built. The database part of miRDRN currently stores 6,973,875 p-valued RSPs associated with 116 diseases in 78 tissue types built from 207 diseases-associated miRNA regulating 389 genes. miRDRN also provides facilities for the user to construct disease and tissue-specific miRNA regulatory networks from RSPs it stores, and to download and/or visualize parts or all of the product. User may use miRDRN to explore a single disease, or a disease-pair to gain insights on comorbidity. As demonstrations, miRDRN was applied: to explore the single disease colorectal cancer (CRC), in which 26 novel potential CRC target genes were identified; to study the comorbidity of the disease-pair Alzheimer's disease-Type 2 diabetes, in which 18 novel potential comorbid genes were identified; and, to explore possible causes that may shed light on recent failures of late-phase trials of anti-AD, BACE1 inhibitor drugs, in which genes downstream to BACE1 whose suppression may affect signal transduction were identified.

A developmentally regulated spliced variant of PTBP1 is upregulated in type 1 diabetic hearts

Alternative splicing (AS) is dysregulated in Type 1 diabetic (T1D) hearts but mechanisms responsible are unclear. Here, we provide evidence that the RNA binding protein (RBP) PTBP1 is modulated in adult T1D hearts contributing to AS changes. We show that a spliced variant of PTBP1 that is highly expressed in normal newborn mouse hearts is aberrantly expressed in adult T1D mouse hearts. Comparing known PTBP1-target datasets to our T1D mouse transcriptome datasets, we discovered a group of genes with PTBP1 binding sites in their pre-mRNAs that are differentially spliced in T1D mouse hearts. We demonstrated that inducible expression of diabetes-induced PTBP1 spliced variant has less repressive splicing function. Notably, PTBP1 regulates AS of some of its targets antagonistically to RBFOX2. In sum, our results indicate that diabetic conditions disrupt developmental regulation of PTBP1 leading to differential AS of PTBP1 target genes. Identification of PTBP1 and PTBP1-regulated RNA networks can provide RNA-based therapies for the treatment of diabetes cardiac complications.