Long Noncoding RNA lncMUMA Reverses Established Skeletal Muscle Atrophy following Mechanical Unloading

The long noncoding RNA lncMPD2 inhibits myogenesis by targeting the miR-34a-5p/THBS1 axis

Long noncoding RNAs (lncRNAs) participate in regulating skeletal muscle development. However, little is known about their role in regulating chicken myogenesis. In this study, we identified a novel lncRNA, lncMPD2, through transcriptome sequencing of chicken myoblasts at different developmental stages. Functionally, gain- and loss-of-function experiments showed that lncMPD2 inhibited myoblast proliferation and differentiation. Mechanistically, lncMPD2 directly bound to miR-34a-5p, and miR-34a-5p promoted myoblasts proliferation and differentiation and inhibited the mRNA and protein expression of its target gene THBS1. THBS1 inhibited myoblast proliferation and differentiation in vitro and delayed muscle regeneration in vivo. Furthermore, rescue experiments showed that lncMPD2 counteracted the inhibitory effects of miR-34a-5p on THBS1 and myogenesis-related gene mRNA and protein expression. In conclusion, lncMPD2 regulates the miR-34a-5p/THBS1 axis to inhibit the proliferation and differentiation of myoblasts and skeletal muscle regeneration. This study provides more insight into the molecular regulatory network of skeletal muscle development, identifying novel potential biomarkers for improving chicken quality and increasing chicken yield. In addition, this study provides a potential goal for breeding strategies that minimize muscle damage in chickens.

Long non-coding RNAs and their role in muscle regeneration

In mammals, most of the genome is transcribed to generate a large and heterogeneous variety of non-protein coding RNAs, that are broadly grouped according to their size. Long noncoding RNAs include a very large and versatile group of molecules. Despite only a minority of them has been functionally characterized, there is emerging evidence indicating long noncoding RNAs as important regulators of expression at multiple levels. Several of them have been shown to be modulated during myogenic differentiation, playing important roles in the regulation of skeletal muscle development, differentiation and homeostasis, and contributing to neuromuscular diseases. In this chapter, we have summarized the current knowledge about long noncoding RNAs in skeletal muscle and discussed specific examples of long noncoding RNAs (lncRNAs and circRNAs) regulating muscle stem cell biology. We have also discussed selected long noncoding RNAs involved in the most common neuromuscular diseases.

Long non-coding RNA-NONMMMUT004552.2 regulates the unloading-induced bone loss through the miRNA-15b-5p/Syne1 in mice

Exercise-induced mechanical loading can increase bone strength whilst mechanical unloading enhances bone-loss. Here, we investigated the role of lncRNA NONMMUT004552.2 in unloading-induced bone-loss. Knockout of lncRNA NONMMUT004552.2 in hindlimb-unloaded mice caused an increase in the bone formation and osteoblast activity. The silencing of lncRNA NONMMUT004552.2 also decreased the osteoblast apoptosis and expression of Bax and cleaved caspase-3, increased Bcl-2 protein expression in MC3T3-E1 cells. Mechanistic investigations demonstrated that NONMMUT004552.2 functions as a competing endogenous RNA (ceRNA) to facilitate the protein expression of spectrin repeat containing, nuclear envelope 1 (Syne1) by competitively binding miR-15b-5p and subsequently inhibits the osteoblast differentiation and bone formation in the microgravity unloading environment. These data highlight the importance of the lncRNA NONMMUT004552.2/miR-15b-5p/Syne1 axis for the treatment of osteoporosis.

Construction of LncRNA-Related ceRNA Networks in Longissimus Dorsi Muscle of Jinfen White Pigs at Different Developmental Stages

The development of skeletal muscle in pigs might determine the quality of pork. In recent years, long non-coding RNAs (lncRNAs) have been found to play an important role in skeletal muscle growth and development. In this study, we investigated the whole transcriptome of the longissimus dorsi muscle (LDM) of Jinfen White pigs at three developmental stages (1, 90, and 180 days) and performed a comprehensive analysis of lncRNAs, mRNAs, and micro-RNAs (miRNAs), aiming to find the key regulators and interaction networks in Jinfen White pigs. A total of 2638 differentially expressed mRNAs (DE mRNAs) and 982 differentially expressed lncRNAs (DE lncRNAs) were identified. Compared with JFW_1d, there were 497 up-regulated and 698 down-regulated DE mRNAs and 212 up-regulated and 286 down-regulated DE lncRNAs in JFW_90d, respectively. In JFW_180d, there were 613 up-regulated and 895 down-regulated DE mRNAs and 184 up-regulated and 131 down-regulated DE lncRNAs compared with JFW_1d. There were 615 up-regulated and 477 down-regulated DE mRNAs and 254 up-regulated and 355 down-regulated DE lncRNAs in JFW_180d compared with JFW_90d. Compared with mRNA, lncRNA has fewer exons, fewer ORFs, and a shorter length. We performed GO and KEGG pathway functional enrichment analysis for DE mRNAs and the potential target genes of DE lncRNAs. As a result, several pathways are involved in muscle growth and development, such as the PI3K-Akt, MAPK, hedgehog, and hippo signaling pathways. These are among the pathways through which mRNA and lncRNAs function. As part of this study, bioinformatic screening was used to identify miRNAs and DE lncRNAs that could act as ceRNAs. Finally, we constructed an lncRNA-miRNA-mRNA regulation network containing 26 mRNAs, 7 miRNAs, and 17 lncRNAs; qRT-PCR was used to verify the key genes in these networks. Among these, XLOC_022984/miR-127/ENAH and XLOC_016847/miR-486/NRF1 may function as key ceRNA networks. In this study, we obtained transcriptomic profiles from the LDM of Jinfen White pigs at three developmental stages and screened out lncRNA-miRNA-mRNA regulatory networks that may provide crucial information for the further exploration of the molecular mechanisms during skeletal muscle development.

Role of Long Non-coding RNA in Nerve Regeneration

Nerve injury can be caused by a variety of factors. It often takes a long time to repair a nerve injury and severe nerve injury is even difficult to heal. Therefore, increasing attention has focused on nerve injury and repair. Long non-coding RNA (lncRNA) is a newly discovered non-coding RNA with a wide range of biological activities. Numerous studies have shown that a variety of lncRNAs undergo changes in expression after nerve injury, indicating that lncRNAs may be involved in various biological processes of nerve repair and regeneration. Herein, we summarize the biological roles of lncRNAs in neurons, glial cells and other cells during nerve injury and regeneration, which will help lncRNAs to be better applied in nerve injury and regeneration in the future.

Mitochondrial dysfunction and skeletal muscle atrophy: Causes, mechanisms, and treatment strategies

Skeletal muscle, which accounts for approximately 40% of total body weight, is one of the most dynamic and plastic tissues in the human body and plays a vital role in movement, posture and force production. More than just a component of the locomotor system, skeletal muscle functions as an endocrine organ capable of producing and secreting hundreds of bioactive molecules. Therefore, maintaining healthy skeletal muscles is crucial for supporting overall body health. Various pathological conditions, such as prolonged immobilization, cachexia, aging, drug-induced toxicity, and cardiovascular diseases (CVDs), can disrupt the balance between muscle protein synthesis and degradation, leading to skeletal muscle atrophy. Mitochondrial dysfunction is a major contributing mechanism to skeletal muscle atrophy, as it plays crucial roles in various biological processes, including energy production, metabolic flexibility, maintenance of redox homeostasis, and regulation of apoptosis. In this review, we critically examine recent knowledge regarding the causes of muscle atrophy (disuse, cachexia, aging, etc.) and its contribution to CVDs. Additionally, we highlight the mitochondrial signaling pathways involvement to skeletal muscle atrophy, such as the ubiquitin-proteasome system, autophagy and mitophagy, mitochondrial fission-fusion, and mitochondrial biogenesis. Furthermore, we discuss current strategies, including exercise, mitochondria-targeted antioxidants, in vivo transfection of PGC-1α, and the potential use of mitochondrial transplantation as a possible therapeutic approach.

Metabolic reprogramming in cancer: Mechanisms and therapeutics

Cancer cells characterized by uncontrolled growth and proliferation require altered metabolic processes to maintain this characteristic. Metabolic reprogramming is a process mediated by various factors, including oncogenes, tumor suppressor genes, changes in growth factors, and tumor–host cell interactions, which help to meet the needs of cancer cell anabolism and promote tumor development. Metabolic reprogramming in tumor cells is dynamically variable, depending on the tumor type and microenvironment, and reprogramming involves multiple metabolic pathways. These metabolic pathways have complex mechanisms and involve the coordination of various signaling molecules, proteins, and enzymes, which increases the resistance of tumor cells to traditional antitumor therapies. With the development of cancer therapies, metabolic reprogramming has been recognized as a new therapeutic target for metabolic changes in tumor cells. Therefore, understanding how multiple metabolic pathways in cancer cells change can provide a reference for the development of new therapies for tumor treatment. Here, we systemically reviewed the metabolic changes and their alteration factors, together with the current tumor regulation treatments and other possible treatments that are still under investigation. Continuous efforts are needed to further explore the mechanism of cancer metabolism reprogramming and corresponding metabolic treatments.

The retroelement Lx9 puts a brake on the immune response to virus infection

The notion that mobile units of nucleic acid known as transposable elements can operate as genomic controlling elements was put forward over six decades ago^1,2. However, it was not until the advancement of genomic sequencing technologies that the abundance and repertoire of transposable elements were revealed, and they are now known to constitute up to two-thirds of mammalian genomes^3,4. The presence of DNA regulatory regions including promoters, enhancers and transcription-factor-binding sites within transposable elements^5-8 has led to the hypothesis that transposable elements have been co-opted to regulate mammalian gene expression and cell phenotype^8-14. Mammalian transposable elements include recent acquisitions and ancient transposable elements that have been maintained in the genome over evolutionary time. The presence of ancient conserved transposable elements correlates positively with the likelihood of a regulatory function, but functional validation remains an essential step to identify transposable element insertions that have a positive effect on fitness. Here we show that CRISPR-Cas9-mediated deletion of a transposable element-namely the LINE-1 retrotransposon Lx9c11-in mice results in an exaggerated and lethal immune response to virus infection. Lx9c11 is critical for the neogenesis of a non-coding RNA (Lx9c11-RegoS) that regulates genes of the Schlafen family, reduces the hyperinflammatory phenotype and rescues lethality in virus-infected Lx9c11^-/- mice. These findings provide evidence that a transposable element can control the immune system to favour host survival during virus infection.

The Functional Role of Long Non-Coding RNA in Myogenesis and Skeletal Muscle Atrophy

Skeletal muscle is a pivotal organ in humans that maintains locomotion and homeostasis. Muscle atrophy caused by sarcopenia and cachexia, which results in reduced muscle mass and impaired skeletal muscle function, is a serious health condition that decreases life longevity in humans. Recent studies have revealed the molecular mechanisms by which long non-coding RNAs (lncRNAs) regulate skeletal muscle mass and function through transcriptional regulation, fiber-type switching, and skeletal muscle cell proliferation. In addition, lncRNAs function as natural inhibitors of microRNAs and induce muscle hypertrophy or atrophy. Intriguingly, muscle atrophy modifies the expression of thousands of lncRNAs. Therefore, although their exact functions have not yet been fully elucidated, various novel lncRNAs associated with muscle atrophy have been identified. Here, we comprehensively review recent knowledge on the regulatory roles of lncRNAs in skeletal muscle atrophy. In addition, we discuss the issues and possibilities of targeting lncRNAs as a treatment for skeletal muscle atrophy and muscle wasting disorders in humans.

LncRNA SMARCD3-OT1 Promotes Muscle Hypertrophy and Fast-Twitch Fiber Transformation via Enhancing SMARCD3X4 Expression

Long noncoding RNA (lncRNA) plays a crucial part in all kinds of life activities, especially in myogenesis. SMARCD3 (SWI/SNF-related, matrix-associated, actin-dependent regulator of chromatin, subfamily d, member 3) is a member of the SWI/SNF protein complex and was reported to be required for cell proliferation and myoblast differentiation. In this study, we identified a new lncRNA named SMARCD3-OT1 (SMARCD3overlappinglncRNA), which strongly regulated the development of myogenesis by improving the expression of SMARCD3X4 (SMARCD3transcripts4). We overexpressed and knockdown the expression of SMARCD3-OT1 and SMARCD3X4 to investigate their function on myoblast proliferation and differentiation. Cell experiments proved that SMARCD3-OT1 and SMARCD3X4 promoted myoblast proliferation through the CDKN1A pathway and improved differentiation of differentiated myoblasts through the MYOD pathway. Moreover, they upregulated the fast-twitch fiber-related genes and downregulated the slow-twitch fiber-related genes, which indicated that they facilitated the slow-twitch fiber to transform into the fast-twitch fiber. The animals’ experiments supported the results above, demonstrating that SMARCD3-OT1 could induce muscle hypertrophy and fast-twitch fiber transformation. In conclusion, SMARCD3-OT1 can improve the expression of SMARCD3X4, thus inducing muscle hypertrophy. In addition, SMARCD3-OT1 can facilitate slow-twitch fibers to transform into fast-twitch fibers.

A Quartet Network Analysis Identifying Mechanically Responsive Long Noncoding RNAs in Bone Remodeling

Mechanical force, being so ubiquitous that it is often taken for granted and overlooked, is now gaining the spotlight for reams of evidence corroborating their crucial roles in the living body. The bone, particularly, experiences manifold extraneous force like strain and compression, as well as intrinsic cues like fluid shear stress and physical properties of the microenvironment. Though sparkled in diversified background, long noncoding RNAs (lncRNAs) concerning the mechanotransduction process that bone undergoes are not yet detailed in a systematic way. Our principal goal in this research is to highlight the potential lncRNA-focused mechanical signaling systems which may be adapted by bone-related cells for biophysical environment response. Based on credible lists of force-sensitive mRNAs and miRNAs, we constructed a force-responsive competing endogenous RNA network for lncRNA identification. To elucidate the underlying mechanism, we then illustrated the possible crosstalk between lncRNAs and mRNAs as well as transcriptional factors and mapped lncRNAs to known signaling pathways involved in bone remodeling and mechanotransduction. Last, we developed combinative analysis between predicted and established lncRNAs, constructing a pathway–lncRNA network which suggests interactive relationships and new roles of known factors such as H19. In conclusion, our work provided a systematic quartet network analysis, uncovered candidate force-related lncRNAs, and highlighted both the upstream and downstream processes that are possibly involved. A new mode of bioinformatic analysis integrating sequencing data, literature retrieval, and computational algorithm was also introduced. Hopefully, our work would provide a moment of clarity against the multiplicity and complexity of the lncRNA world confronting mechanical input.

LncEDCH1 improves mitochondrial function to reduce muscle atrophy by interacting with SERCA2

Skeletal muscle is a regulator of the body's energy expenditure and metabolism. Abnormal regulation of skeletal muscle-specific genes leads to various muscle diseases. Long non-coding RNAs (lncRNAs) have been demonstrated to play important roles in muscle growth and muscle atrophy. To explore the potential function of muscle-associated lncRNA, we analyzed our previous RNA-sequencing data and selected the lncRNA (LncEDCH1) as the research object. In this study, we report that LncEDCH1 is specifically enriched in skeletal muscle, and its transcriptional activity is positively regulated by transcription factor SP1. LncEDCH1 regulates myoblast proliferation and differentiation in vitro. In vivo, LncEDCH1 reduces intramuscular fat deposition, activates slow-twitch muscle phenotype, and inhibits muscle atrophy. Mechanistically, LncEDCH1 binds to sarcoplasmic/ER calcium ATPase 2 (SERCA2) protein to enhance SERCA2 protein stability and increase SERCA2 activity. Meanwhile, LncEDCH1 improves mitochondrial efficiency possibly through a SERCA2-mediated activation of the AMPK pathway. Our findings provide a strategy for using LncEDCH1 as an effective regulator for the treatment of muscle atrophy and energy metabolism.

Fast and slow myofiber-specific expression profiles are affected by noncoding RNAs in Mongolian horses

The heterogeneity and plasticity of muscle fibers are essential for the athletic performance of horses, mainly at the adaption of exercises and the effect on muscle diseases. Skeletal muscle fibers can be generally distinguished by their characteristics of contraction as slow and fast type myofibers. The diversity of contractile properties and metabolism enable skeletal muscles to respond to the variable functional requirements. We investigated the muscle fiber composition and metabolic enzyme activities of splenius muscle and gluteus medius muscle from Mongolian horses. The deep RNA-seq analysis of detecting differentially expressed mRNAs, lncRNAs, circRNAs and their correlation analysis from two muscles were performed. Splenius muscle and gluteus medius muscle from Mongolian horses showed a high divergence of myofiber compositions and metabolic enzyme activities. Corresponding to their phenotypic characteristics, 57 differentially expressed long noncoding RNAs and 12 differentially expressed circle RNAs were found between two muscles. The analysis results indicate multiple binding sites were detected in lncRNAs and circRNAs with myofiber-specific expressed miRNAs. Among which we found significant correlations between the above noncoding RNAs, miRNAs, their target genes, myofiber-specific developmental transcript factors, and sarcomere genes. We suggest that the ceRNA mechanism of differentially expressed noncoding RNAs by acting as miRNA sponges could be fine tuners in regulating skeletal muscle fiber composition and transition in horses, which will operate new protective measures of muscle disease and locomotor adaption for racehorses.

Factors mediating spaceflight-induced skeletal muscle atrophy

Skeletal muscle atrophy is a well-known consequence of spaceflight. Because of the potential significant impact of muscle atrophy and muscle dysfunction on astronauts and to their mission, a thorough understanding of the mechanisms of this atrophy and the development of effective countermeasures is critical. Spaceflight-induced muscle atrophy is similar to atrophy seen in many terrestrial conditions, and therefore our understanding of this form of atrophy may also contribute to the treatment of atrophy in humans on Earth. The unique environmental features humans encounter in space include the weightlessness of microgravity, space radiation, and the distinctive aspects of living in a spacecraft. The disuse and unloading of muscles in microgravity are likely the most significant factors that mediate spaceflight-induced muscle atrophy, and have been extensively studied and reviewed. However, there are numerous other direct and indirect effects on skeletal muscle that may be contributing factors to the muscle atrophy and dysfunction seen as a result of spaceflight. This review offers a novel perspective on the issue of muscle atrophy in space by providing a comprehensive overview of the unique aspects of the spaceflight environment and the various ways in which they can lead to muscle atrophy. We systematically review the potential contributions of these different mechanisms of spaceflight-induced atrophy and include findings from both actual spaceflight and ground-based models of spaceflight in humans, animals, and in vitro studies.

Role of lncRNAs into Mesenchymal Stromal Cell Differentiation

Currently, findings support that 75% of the human genome is actively transcribed, but only 2% is translated into a protein, according to databases such as ENCODE (Encyclopedia of DNA Elements) [1]. The development of high-throughput sequencing technologies, computational methods for genome assembly and biological models have led to the realization of the importance of the previously unconsidered non-coding fraction of the genome. Along with this, noncoding RNAs have been shown to be epigenetic, transcriptional and post-transcriptional regulators in a large number of cellular processes [2]. Within the group of non-coding RNAs, lncRNAs represent a fascinating field of study, given the functional versatility in their mode of action on their molecular targets. In recent years, there has been an interest in learning about lncRNAs in MSC differentiation. The aim of this review is to address the signaling mechanisms where lncRNAs are involved, emphasizing their role in either stimulating or inhibiting the transition to differentiated cell. Specifically, the main types of MSC differentiation are discussed: myogenesis, osteogenesis, adipogenesis and chondrogenesis. The description of increasingly new lncRNAs reinforces their role as players in the well-studied field of MSC differentiation, allowing a step towards a better understanding of their biology and their potential application in the clinic.

Muscle Regeneration and RNA: New Perspectives for Ancient Molecules

The ability of the ribonucleic acid (RNA) to self-replicate, combined with a unique cocktail of chemical properties, suggested the existence of an RNA world at the origin of life. Nowadays, this hypothesis is supported by innovative high-throughput and biochemical approaches, which definitively revealed the essential contribution of RNA-mediated mechanisms to the regulation of fundamental processes of life. With the recent development of SARS-CoV-2 mRNA-based vaccines, the potential of RNA as a therapeutic tool has received public attention. Due to its intrinsic single-stranded nature and the ease with which it is synthesized in vitro, RNA indeed represents the most suitable tool for the development of drugs encompassing every type of human pathology. The maximum effectiveness and biochemical versatility is achieved in the guise of non-coding RNAs (ncRNAs), which are emerging as multifaceted regulators of tissue specification and homeostasis. Here, we report examples of coding and ncRNAs involved in muscle regeneration and discuss their potential as therapeutic tools. Small ncRNAs, such as miRNA and siRNA, have been successfully applied in the treatment of several diseases. The use of longer molecules, such as lncRNA and circRNA, is less advanced. However, based on the peculiar properties discussed below, they represent an innovative pool of RNA biomarkers and possible targets of clinical value.

Lnc-GD2H Promotes Proliferation by Forming a Feedback Loop With c-Myc and Enhances Differentiation Through Interacting With NACA to Upregulate Myog in C2C12 Myoblasts

In the present study, the roles of a novel long non-coding RNA (lncRNA), lnc-GD2H, in promoting C2C12 myoblast proliferation and differentiation and muscle regeneration were investigated by quantitative polymerase chain reaction, western blotting, Cell Counting Kit-8, 5-ethynyl-2′-deoxyuridine (EdU), immunofluorescence staining, luciferase reporter, mass spectrometry, pulldown, chromatin immunoprecipitation, RNA immunoprecipitation assay, wound healing assays, and cardiotoxin (CTX)-induced muscle injury assays. It was observed that lnc-GD2H promoted myoblast proliferation as evidenced by the enhancement of the proliferation markers c-Myc, CDK2, CDK4, and CDK6, percentage of EdU-positive cells, and rate of cell survival during C2C12 myoblast proliferation. Additional experiments confirmed that c-Myc bound to the lnc-GD2H promoter and regulated its transcription. lnc-GD2H promoted cell differentiation with enhanced MyHC immunostaining as well as increased expression of the myogenic marker genes myogenin (Myog), Mef2a, and Mef2c during myoblast differentiation. Additional assays indicated that lnc-GD2H interacted with NACA which plays a role of transcriptional regulation in myoblast differentiation, and the enrichment of NACA at the Myog promoter was impaired by lnc-GD2H. Furthermore, inhibition of lnc-GD2H impaired muscle regeneration after CTX-induced injury in mice. lnc-GD2H facilitated the expression of proliferating marker genes and formed a feedback loop with c-Myc during myoblast proliferation. In differentiating myoblasts, lnc-GD2H interacted with NACA to relieve the inhibitory effect of NACA on Myog, facilitating Myog expression to promote differentiation. The results provide evidence for the role of lncRNAs in muscle regeneration and are useful for developing novel therapeutic targets for muscle disorders.

Cerium Oxide Nanoparticle Administration to Skeletal Muscle Cells under Different Gravity and Radiation Conditions

For their remarkable biomimetic properties implying strong modulation of the intracellular and extracellular redox state, cerium oxide nanoparticles (also termed "nanoceria") were hypothesized to exert a protective role against oxidative stress associated with the harsh environmental conditions of spaceflight, characterized by microgravity and highly energetic radiations. Nanoparticles were supplied to proliferating C2C12 mouse skeletal muscle cells under different gravity and radiation levels. Biological responses were thus investigated at a transcriptional level by RNA next-generation sequencing. Lists of differentially expressed genes (DEGs) were generated and intersected by taking into consideration relevant comparisons, which led to the observation of prevailing effects of the space environment over those induced by nanoceria. In space, upregulation of transcription was slightly preponderant over downregulation, implying involvement of intracellular compartments, with the majority of DEGs consistently over- or under-expressed whenever present. Cosmic radiations regulated a higher number of DEGs than microgravity and seemed to promote increased cellular catabolism. By taking into consideration space physical stressors alone, microgravity and cosmic radiations appeared to have opposite effects at transcriptional levels despite partial sharing of molecular pathways. Interestingly, gene ontology denoted some enrichment in terms related to vision, when only effects of radiations were assessed. The transcriptional regulation of mitochondrial uncoupling protein 2 in space-relevant samples suggests perturbation of the intracellular redox homeostasis, and leaves open opportunities for antioxidant treatment for oxidative stress reduction in harsh environments.

Transcriptome profiling of the diaphragm in a controlled mechanical ventilation model reveals key genes involved in ventilator-induced diaphragmatic dysfunction

BACKGROUND

Ventilator-induced diaphragmatic dysfunction (VIDD) is associated with weaning difficulties, intensive care unit hospitalization (ICU), infant mortality, and poor long-term clinical outcomes. The expression patterns of long noncoding RNAs (lncRNAs) and mRNAs in the diaphragm in a rat controlled mechanical ventilation (CMV) model, however, remain to be investigated.

RESULTS

The diaphragms of five male Wistar rats in a CMV group and five control Wistar rats were used to explore lncRNA and mRNA expression profiles by RNA-sequencing (RNA-seq). Muscle force measurements and immunofluorescence (IF) staining were used to verify the successful establishment of the CMV model. A total of 906 differentially expressed (DE) lncRNAs and 2,139 DE mRNAs were found in the CMV group. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were performed to determine the biological functions or pathways of these DE mRNAs. Our results revealed that these DE mRNAs were related mainly related to complement and coagulation cascades, the PPAR signaling pathway, cholesterol metabolism, cytokine-cytokine receptor interaction, and the AMPK signaling pathway. Some DE lncRNAs and DE mRNAs determined by RNA-seq were validated by quantitative real-time polymerase chain reaction (qRT-PCR), which exhibited trends similar to those observed by RNA-sEq. Co-expression network analysis indicated that three selected muscle atrophy-related mRNAs (Myog, Trim63, and Fbxo32) were coexpressed with relatively newly discovered DE lncRNAs.

CONCLUSIONS

This study provides a novel perspective on the molecular mechanism of DE lncRNAs and mRNAs in a CMV model, and indicates that the inflammatory signaling pathway and lipid metabolism may play important roles in the pathophysiological mechanism and progression of VIDD.

Functional roles of non-coding RNAs in atrophy

Atrophy is defined as a reduction in cell, organ, or tissue size after reaching their normal mature sizes because of loss of organelles, cytoplasmic compartments, and proteins. This process is also involved in the pathogenesis of human disorders. Inadequate nourishment, poor circulation, inadequate hormonal support, defects in nerve supply of the tissue, disproportionate induction of apoptosis in the tissue, and absence of exercise are some underlying causes of atrophy. Recently, several non-coding RNAs (ncRNAs) have been identified that regulate atrophy, thus participating in the pathobiology of related disorders such as neurodegenerative/ neuromuscular diseases, age-related muscle atrophy, and cardiac tissue atrophy. In the current review, we have focused on two classes of ncRNAs namely long ncRNAs (lncRNAs) and microRNAs (miRNAs) to unravel their participation in atrophy-associated disorders.

Aberrant lncRNA Profiles Are Associated With Chronic Benzene Poisoning and Acute Myelocytic Leukemia

OBJECTIVE

This study investigates the mechanisms of benzene hematotoxicity.

METHODS

We used microarray to detect expression profiles of long non-coding RNAs (lncRNAs) and mRNAs in peripheral lymphocytes from chronic benzene poisoning, acute myelocytic leukemia, and healthy controls. The lncRNAs and mRNAs were validated using real-time quantitative PCR (RT-qPCR). Cytokinesis-block micronucleus assay was used to analyze chromosomal aberration.

RESULTS

We found 173 upregulated and 258 downregulated lncRNAs, and 695 upregulated and 804 downregulated mRNAs. The lncRNA CUST_40243 and mRNA PDGFC and CDKN1A associated with chronic benzene poisoning. Relevant inflammatory response, hematopoietic cell lineage, and cell cycle may be important pathways for the sifted lncRNAs and mRNAs. Furthermore, micronuclei frequency was significantly higher in off-post chronic benzene poisoning patients.

CONCLUSIONS

Chromosomal aberration induced by benzene exposure is irreversible. The lncRNA CUST_40243 and mRNA PDGFC and CDKN1A are related to chronic benzene poisoning.

LncRNAs in adaptive immunity: role in physiological and pathological conditions

The adaptive immune system is responsible for generating immunological response and immunological memory. Regulation of adaptive immunity including B cell and T cell biology was mainly understood from the protein and microRNA perspective. However, long non-coding RNAs (lncRNAs) are an emerging class of non-coding RNAs (ncRNAs) that influence key factors in lymphocyte biology such as NOTCH, PAX5, MYC and EZH2. LncRNAs were described to modulate lymphocyte activation by regulating pathways such as NFAT, NFκB, MYC, interferon and TCR/BCR signalling (NRON, NKILA, BCALM, GAS5, PVT1), and cell effector functions (IFNG-AS1, TH2-LCR). Here we review lncRNA involvement in adaptive immunity and the implications for autoimmune diseases (multiple sclerosis, inflammatory bowel disease, rheumatoid arthritis) and T/B cell leukaemias and lymphomas (CLL, MCL, DLBCL, T-ALL). It is becoming clear that lncRNAs are important in adaptive immune response and provide new insights into its orchestration.

Lnc-ORA interacts with microRNA-532-3p and IGF2BP2 to inhibit skeletal muscle myogenesis

Skeletal muscle is one of the most important organs of the animal body. Long noncoding RNAs play a crucial role in the regulation of skeletal muscle development via several mechanisms. We recently identified obesity-related lncRNA (lnc-ORA) in a search for long noncoding RNAs that influence adipogenesis, finding it impacted adipocyte differentiation by regulating the PI3K/protein kinase B/mammalian target of rapamycin pathway. However, whether lnc-ORA has additional roles, specifically in skeletal muscle myogenesis, is not known. Here, we found that lnc-ORA was significantly differentially expressed with age in mouse skeletal muscle tissue and predominantly located in the cytoplasm. Overexpression of lnc-ORA promoted C2C12 myoblast proliferation and inhibited myoblast differentiation. In contrast, lnc-ORA knockdown repressed myoblast proliferation and facilitated myoblast differentiation. Interestingly, silencing of lnc-ORA rescued dexamethasone-induced muscle atrophy in vitro. Furthermore, adeno-associated virus 9–mediated overexpression of lnc-ORA decreased muscle mass and the cross-sectional area of muscle fiber by upregulating the levels of muscle atrophy–related genes and downregulating the levels of myogenic differentiation–related genes in vivo. Mechanistically, lnc-ORA inhibited skeletal muscle myogenesis by acting as a sponge of miR-532-3p, which targets the phosphatase and tensin homolog gene; the resultant changes in phosphatase and tensin homolog suppressed the PI3K/protein kinase B signaling pathway. In addition, lnc-ORA interacted with insulin-like growth factor 2 mRNA-binding protein 2 and reduced the stability of myogenesis genes, such as myogenic differentiation 1 and myosin heavy chain. Collectively, these findings indicate that lnc-ORA could be a novel underlying regulator of skeletal muscle development.

Role of miRNAs and lncRNAs in dexamethasone-induced myotube atrophy in vitro

Skeletal muscle atrophy is a well-known adverse effect of long-term glucocorticoid (GC) therapy. MicroRNAs (miRNAs or miRs) and long non-coding RNAs (lncRNAs) are important regulators in a number of physiological and pathological processes. However, the role of miRNAs and lncRNAs in the regulation of GC-treated muscle atrophy remains poorly understood. In the current study, muscular atrophy was induced and the results indicated that C2C12 myotubes were thinner than normal, while the expression of muscle ring finger protein 1 and Atrogin-1 was increased. The expression of nine miRNAs and seven lncRNAs associated with proliferation and differentiation were analyzed in a dexamethasone (DEX)-induced muscle atrophy cell model. In addition, the mRNA expression of the downstream targets of lncRNAs that were differentially expressed between DEX-treated and control cells were determined. The results indicated that the expression of miR-133a, miR-133b, miR-206 and five lncRNAs (increased Atrolnc-1, Dum, MAR1, linc-MD1 and decreased Myolinc) were significantly different between the DEX and the control group. Furthermore, the relative mRNA expression of Wnt5a and MyoD was significantly different between the two groups. The results of the current study indicated that some important miRNAs and lncRNAs are associated with DEX-induced muscle atrophy and have the potential to be further developed as a diagnostic tool for this condition.

Long noncoding RNA SMUL suppresses SMURF2 production-mediated muscle atrophy via nonsense-mediated mRNA decay

As the world population grows, muscle atrophy leading to muscle wasting could become a bigger risk. Long noncoding RNAs (lncRNAs) are known to play important roles in muscle growth and muscle atrophy. Meanwhile, it has recently come to light that many putative small open reading frames (sORFs) are hidden in lncRNAs; however, their translational capabilities and functions remain unclear. In this study, we uncovered 104 myogenic-associated lncRNAs translated, in at least a small peptide, by integrated transcriptome and proteomic analyses. Furthermore, an upstream ORF (uORF) regulatory network was constructed, and a novel muscle atrophy-associated lncRNA named SMUL (Smad ubiquitin regulatory factor 2 [SMURF2] upstream lncRNA) was identified. SMUL was highly expressed in skeletal muscle, and its expression level was downregulated during myoblast differentiation. SMUL promoted myoblast proliferation and suppressed differentiation in vitro. In vivo, SMUL induced skeletal muscle atrophy and promoted a switch from slow-twitch to fast-twitch fibers. In the meantime, translation of the SMUL sORF disrupted the stability of SMURF2 mRNA. Mechanistically, SMUL restrained SMURF2 production via nonsense-mediated mRNA decay (NMD), participating in the regulation of the transforming growth factor β (TGF-β)/SMAD pathway and further regulating myogenesis and muscle atrophy. Taken together, these results suggest that SMUL could be a novel therapeutic target for muscle atrophy.

Inhibition of lncRNA MAAT Controls Multiple Types of Muscle Atrophy by cis- and trans-Regulatory Actions

Muscle atrophy is associated with negative outcomes in a variety of diseases. Identification of a common therapeutic target would address a significant unmet clinical need. Here, we identify a long non-coding RNA (lncRNA) (muscle-atrophy-associated transcript, lncMAAT) as a common regulator of skeletal muscle atrophy. lncMAAT is downregulated in multiple types of muscle-atrophy models both in vivo (denervation, Angiotensin II [AngII], fasting, immobilization, and aging-induced muscle atrophy) and in vitro (AngII, H₂O₂, and tumor necrosis factor alpha [TNF-α]-induced muscle atrophy). Gain- and loss-of-function analysis both in vitro and in vivo reveals that downregulation of lncMAAT is sufficient to induce muscle atrophy, while overexpression of lncMAAT can ameliorate multiple types of muscle atrophy. Mechanistically, lncMAAT negatively regulates the transcription of miR-29b through SOX6 by a trans-regulatory module and increases the expression of the neighboring gene Mbnl1 by a cis-regulatory module. Therefore, overexpression of lncMAAT may represent a promising therapy for muscle atrophy induced by different stimuli.

Long Non-coding RNA H19 Regulates Porcine Satellite Cell Differentiation Through miR-140-5p/SOX4 and DBN1

The H19 gene promotes skeletal muscle differentiation in mice, but the regulatory models and mechanisms of myogenesis regulated by H19 are largely unknown in pigs. Therefore, the regulatory modes of H19 in the differentiation of porcine skeletal muscle satellite cells (PSCs) need to be determined. We observed that H19 gene silencing could decrease the expressions of the myogenin (MYOG) gene, myogenic differentiation (MYOD), and myosin heavy chain (MYHC) in PSCs. Therefore, we constructed and sequenced 12 cDNA libraries of PSCs after knockdown of H19 at two differentiation time points to analyze the transcriptome differences. A total of 11,419 differentially expressed genes (DEGs) were identified. Among these DEGs, we found through bioinformatics analysis and protein interaction experiment that SRY-box transcription factor 4 (SOX4) and Drebrin 1 (DBN1) were the key genes in H19-regulated PSC differentiation. Functional analysis shows that SOX4 and DBN1 promote PSC differentiation. Mechanistically, H19 regulates PSC differentiation through two different pathways. On the one hand, H19 functions as a molecular sponge of miR-140-5p, which inhibits the differentiation of PSCs, thereby modulating the derepression of SOX4. On the other hand, H19 regulates PSC differentiation through directly binding with DBN1. Furthermore, MYOD binds to the promoters of H19 and DBN1. The knockdown of MYOD inhibits the expression of H19 and DBN1. We determined the function of H19 and provided a molecular model to elucidate H19’s role in regulating PSC differentiation.

lncRNA DLEU2 acts as a miR-181a sponge to regulate SEPP1 and inhibit skeletal muscle differentiation and regeneration

Sarcopenia is a serious public health problem associated with the loss of muscle mass and function. The purpose of this study was to identify molecular markers and construct a ceRNA pathway as a significant predictor of sarcopenia. We designed a prediction model to select important differentially expressed mRNAs (DEMs), and constructed a sarcopenia associated ceRNA network. After correlation analysis of each element in the ceRNA network based on clinical samples and GTEX database, C2C12 mouse myoblasts were used as a model to verify the identified ceRNA pathways. A new model for predicting sarcopenia based on four molecular markers SEPP1, SV2A, GOT1, and GFOD1 was developed. The model was used to construct a ceRNA network and showed high accuracy. Correlation analysis showed that the expression levels of lncDLEU2, SEPP1, and miR-181a were closely associated with a high risk of sarcopenia. lncDLEU2 inhibits muscle differentiation and regeneration by acting as a miR-181a sponge regulating SEPP1 expression. In this study, a highly accurate prediction tool was developed to improve the prediction outcomes of sarcopenia. These findings suggest that the lncDLEU2-miR-181a-SEPP1 pathway inhibits muscle differentiation and regeneration. This pathway may be a new therapeutic target for the treatment of sarcopenia.

Regulation of Skeletal Muscle Atrophy in Cachexia by MicroRNAs and Long Non-coding RNAs

Skeletal muscle atrophy is a common complication of cachexia, characterized by progressive bodyweight loss and decreased muscle strength, and it significantly increases the risks of morbidity and mortality in the population with atrophy. Numerous complications associated with decreased muscle function can activate catabolism, reduce anabolism, and impair muscle regeneration, leading to muscle wasting. microRNAs (miRNAs) and long non-coding RNAs (lncRNAs), types of non-coding RNAs, are important for regulation of skeletal muscle development. Few studies have specifically identified the roles of miRNAs and lncRNAs in cellular or animal models of muscular atrophy during cachexia, and the pathogenesis of skeletal muscle wasting in cachexia is not entirely understood. To develop potential approaches to improve skeletal muscle mass, strength, and function, a more comprehensive understanding of the known key pathophysiological processes leading to muscular atrophy is needed. In this review, we summarize the known miRNAs, lncRNAs, and corresponding signaling pathways involved in regulating skeletal muscle atrophy in cachexia and other diseases. A comprehensive understanding of the functions and mechanisms of miRNAs and lncRNAs during skeletal muscle wasting in cachexia and other diseases will, therefore, promote therapeutic treatments for muscle atrophy.

Muscle unloading: A comparison between spaceflight and ground-based models

Prolonged unloading of skeletal muscle, a common outcome of events such as spaceflight, bed rest and hindlimb unloading, can result in extensive metabolic, structural and functional changes in muscle fibres. With advancement in investigations of cellular and molecular mechanisms, understanding of disuse muscle atrophy has significantly increased. However, substantial gaps exist in our understanding of the processes dictating muscle plasticity during unloading, which prevent us from developing effective interventions to combat muscle loss. This review aims to update the status of knowledge and underlying mechanisms leading to cellular and molecular changes in skeletal muscle during unloading. We have also discussed advances in the understanding of contractile dysfunction during spaceflights and in ground-based models of muscle unloading. Additionally, we have elaborated on potential therapeutic interventions that show promising results in boosting muscle mass and strength during mechanical unloading. Finally, we have identified key gaps in our knowledge as well as possible research direction for the future.

Expression Levels of Long Non-Coding RNAs Change in Models of Altered Muscle Activity and Muscle Mass

Skeletal muscle is a highly plastic organ that is necessary for homeostasis and health of the human body. The size of skeletal muscle changes in response to intrinsic and extrinsic stimuli. Although protein-coding RNAs including myostatin, NF-κβ, and insulin-like growth factor-1 (IGF-1), have pivotal roles in determining the skeletal muscle mass, the role of long non-coding RNAs (lncRNAs) in the regulation of skeletal muscle mass remains to be elucidated. Here, we performed expression profiling of nine skeletal muscle differentiation-related lncRNAs (DRR, DUM1, linc-MD1, linc-YY1, LncMyod, Neat1, Myoparr, Malat1, and SRA) and three genomic imprinting-related lncRNAs (Gtl2, H19, and IG-DMR) in mouse skeletal muscle. The expression levels of these lncRNAs were examined by quantitative RT-PCR in six skeletal muscle atrophy models (denervation, casting, tail suspension, dexamethasone-administration, cancer cachexia, and fasting) and two skeletal muscle hypertrophy models (mechanical overload and deficiency of the myostatin gene). Cluster analyses of these lncRNA expression levels were successfully used to categorize the muscle atrophy models into two sub-groups. In addition, the expression of Gtl2, IG-DMR, and DUM1 was altered along with changes in the skeletal muscle size. The overview of the expression levels of lncRNAs in multiple muscle atrophy and hypertrophy models provides a novel insight into the role of lncRNAs in determining the skeletal muscle mass.

Targeted overexpression of the long noncoding RNA ODSM can regulate osteoblast function in vitro and in vivo

Ameliorating bone loss caused by mechanical unloading is a substantial clinical challenge, and the role of noncoding RNAs in this process has attracted increasing attention. In this study, we found that the long noncoding RNA osteoblast differentiation-related lncRNA under simulated microgravity (lncRNA ODSM) could inhibit osteoblast apoptosis and promote osteoblast mineralization in vitro. The increased expression level of the lncRNA ODSM partially reduced apoptosis and promoted differentiation in MC3T3-E1 cells under microgravity unloading conditions, and the effect was partially dependent on miR-139-3p. LncRNA ODSM supplementation in hindlimb-unloaded mice caused a decrease in the number of apoptotic cells in bone tissue and an increase in osteoblast activity. Furthermore, targeted overexpression of the lncRNA ODSM in osteoblasts partially reversed bone loss induced by mechanical unloading at the microstructural and biomechanical levels. These findings are the first to suggest the potential value of the lncRNA ODSM in osteoporosis therapy and the treatment of pathological osteopenia.

Non-coding RNAs Shaping Muscle

In 1957, Francis Crick speculated that RNA, beyond its protein-coding capacity, could have its own function. Decade after decade, this theory was dramatically boosted by the discovery of new classes of non-coding RNAs (ncRNAs), including long ncRNAs (lncRNAs) and circular RNAs (circRNAs), which play a fundamental role in the fine spatio-temporal control of multiple layers of gene expression. Recently, many of these molecules have been identified in a plethora of different tissues, and they have emerged to be more cell-type specific than protein-coding genes. These findings shed light on how ncRNAs are involved in the precise tuning of gene regulatory mechanisms governing tissues homeostasis. In this review, we discuss the recent findings on the mechanisms used by lncRNAs and circRNAs to sustain skeletal and cardiac muscle formation, paying particular attention to the technological developments that, over the last few years, have aided their genome-wide identification and study. Together with lncRNAs and circRNAs, the emerging contribution of Piwi-interacting RNAs and transfer RNA-derived fragments to myogenesis will be also discussed, with a glimpse on the impact of their dysregulation in muscle disorders, such as myopathies, muscle atrophy, and rhabdomyosarcoma degeneration.

Roles of lncRNAs and circRNAs in regulating skeletal muscle development

The multistep biological process of myogenesis is regulated by a variety of myoblast regulators, such as myogenic differentiation antigen, myogenin, myogenic regulatory factor, myocyte enhancer factor2A-D and myosin heavy chain. Proliferation and differentiation during skeletal muscle myogenesis contribute to the physiological function of muscles. Certain non-coding RNAs, including long non-coding RNAs (lncRNAs) and circular RNAs (circRNAs), are involved in the regulation of muscle development, and the aberrant expressions of lncRNAs and circRNAs are associated with muscular diseases. In this review, we summarize the recent advances concerning the roles of lncRNAs and circRNAs in regulating the developmental aspects of myogenesis. These findings have remarkably broadened our understanding of the gene regulation mechanisms governing muscle proliferation and differentiation, which makes it more feasible to design novel preventive, diagnostic and therapeutic strategies for muscle disorders.

Importance of Long Non-coding RNAs in the Development and Disease of Skeletal Muscle and Cardiovascular Lineages

The early mammalian embryo is characterized by the presence of three germ layers-the outer ectoderm, middle mesoderm and inner endoderm. The mesoderm is organized into paraxial, intermediate and lateral plate mesoderm. The musculature, vasculature and heart of the adult body are the major derivatives of mesoderm. Tracing back the developmental process to generate these specialized tissues has sparked much interest in the field of regenerative medicine focusing on generating specialized tissues to treat patients with degenerative diseases. Several Long Non-Coding RNAs (lncRNAs) have been identified as regulators of development, proliferation and differentiation of various tissues of mesodermal origin. A better understanding of lncRNAs that can regulate the development of these tissues will open potential avenues for their therapeutic utility and enhance our knowledge about disease progression and development. In this review, we aim to summarize the functions and mechanisms of lncRNAs regulating the early mesoderm differentiation, development and homeostasis of skeletal muscle and cardiovascular system with an emphasis on their therapeutic potential.

Functions and Regulatory Mechanisms of lncRNAs in Skeletal Myogenesis, Muscle Disease and Meat Production

Myogenesis is a complex biological process, and understanding the regulatory network of skeletal myogenesis will contribute to the treatment of human muscle related diseases and improvement of agricultural animal meat production. Long noncoding RNAs (lncRNAs) serve as regulators in gene expression networks, and participate in various biological processes. Recent studies have identified functional lncRNAs involved in skeletal muscle development and disease. These lncRNAs regulate the proliferation, differentiation, and fusion of myoblasts through multiple mechanisms, such as chromatin modification, transcription regulation, and microRNA sponge activity. In this review, we presented the latest advances regarding the functions and regulatory activities of lncRNAs involved in muscle development, muscle disease, and meat production. Moreover, challenges and future perspectives related to the identification of functional lncRNAs were also discussed.

Expression patterns of regulatory lncRNAs and miRNAs in muscular atrophy models induced by starvation in vitro and in vivo

Starvation or severe deprivation of nutrients, which is commonly seen in surgical patients, can result in catabolic changes in skeletal muscles, such as muscle atrophy. Therefore, it is important to elucidate the underlying molecular regulatory mechanisms during skeletal muscle atrophy. In the present study, muscular atrophy was induced by starvation and the results demonstrated that myosin heavy chain was decreased, whereas muscle RING finger protein 1 and atrogin-1 were increased, both in vitro and in vivo. The impact of starvation on the expression patterns of long non-coding RNAs (lncRNAs) and microRNAs (miRNAs) was next determined. The expression patterns of miR-23a, miR-206 and miR-27b in the starved mice exhibited similar trends as those in starved C2C12 cells in vitro, whereas the expression patterns of six other miRNAs (miR-18a, miR-133a, miR-133b, miR-186, miR-1a and miR-29b) differed between the in vivo and the in vitro starvation models. The present study indicated that in vitro expression of the selected miRNAs was not completely consistent with that in vivo. By contrast, lncRNAs showed excellent consistency in their expression patterns in both the in vitro and in vivo starvation models; six of the lncRNAs (Atrolnc-1, long intergenic non-protein coding RNA of muscle differentiation 1, Myolinc, lncRNA myogenic differentiation 1, Dum and muscle anabolic regulator 1) were significantly elevated in starved tissues and cells, while lnc-mg was significantly decreased, compared with the control groups. Thus, lncRNAs involved in muscle atrophy have the potential to be developed as diagnostic tools.

Non-Coding RNA Regulates the Myogenesis of Skeletal Muscle Satellite Cells, Injury Repair and Diseases

Skeletal muscle myogenesis and injury-induced muscle regeneration contribute to muscle formation and maintenance. As myogenic stem cells, skeletal muscle satellite cells have the ability to proliferate, differentiate and self-renew, and are involved in muscle formation and muscle injury repair. Accumulating evidence suggests that non-coding RNAs (ncRNAs), including microRNAs (miRNAs), long non-coding RNAs (lncRNAs) and circular RNAs (circRNAs), are widely involved in the regulation of gene expression during skeletal muscle myogenesis, and their abnormal expression is associated with a variety of muscle diseases. From the perspective of the molecular mechanism and mode of action of ncRNAs in myogenesis, this review aims to summarize the role of ncRNAs in skeletal muscle satellite cells’ myogenic differentiation and in muscle disease, and systematically analyze the mechanism of ncRNAs in skeletal muscle development. This work will systematically summarize the role of ncRNAs in myogenesis and provide reference targets for the treatment of various muscle diseases, such as muscle dystrophy, atrophy and aberrant hypertrophy.

The LncRNA XIRP2-AS1 predicts favorable prognosis in colon cancer

Background

Colorectal cancer is a heterogeneous disease with complex genetic and epigenetic changes. LncRNA has recently been regarded as the biomarker in cancers. Novel biomarkers in colon cancer need to be identified.

Purpose

The objective of this study was to identify the differentially expressed lncRNAs between colon cancer tissue and adjacent tissue, as well as to explore its biological functions.

Patients and methods

There were 130 colon cancer patients included in this study. Of them, 6 colon cancer samples and 3 normal samples were selected for microarray profiling. Another 121 colon cancer samples with complete clinical information were used for immunohistochemical assay and survival analysis. Microarray analysis was performed to determine the differentially expressed lncRNAs between colon cancer tissue and adjacent tissue. Gain-of-function experiments was conducted in vitro and in vivo. In situ hybridization and survival analysis were applied to determine the prognostic impact on survival.

Results

LncRNA XIRP2-AS1 was significantly less expressed in colon cancer tissue. XIRP2-AS1 was remarkably downregulated in colon cancer tissues and cell lines. Functionally, XIRP2-AS1 could inhibit the proliferation and invasion ability of colon cancer cells in vitro and in vivo. Clinical sample analysis showed that XIRP2-AS1 had a favorable impact on the overall survival and progression free survival of patients with colon cancer. miR-182 was validated as the target of XIRP2-AS1 according to luciferase reporter assays, RNA immunoprecipitation and RNA pull down.

Conclusions

Our results suggested that XIRP2-AS1 may act as a favorable biomarker for patients with colon cancer.

Long Non-Coding RNA Myoparr Regulates GDF5 Expression in Denervated Mouse Skeletal Muscle

Skeletal muscle is a highly plastic tissue and decreased skeletal muscle mass (muscle atrophy) results in deteriorated motor function and perturbed body homeostasis. Myogenin promoter-associated long non-coding RNA (lncRNA) Myoparr promotes skeletal muscle atrophy caused by surgical denervation; however, the precise molecular mechanism remains unclear. Here, we examined the downstream genes of Myoparr during muscle atrophy following denervation of tibialis anterior (TA) muscles in C57BL/6J mice. Myoparr knockdown affected the expression of 848 genes. Sixty-five of the genes differentially regulated by Myoparr knockdown coded secretory proteins. Among these 65 genes identified in Myoparr-depleted skeletal muscles after denervation, we focused on the increased expression of growth/differentiation factor 5 (GDF5), an inhibitor of muscle atrophy. Myoparr knockdown led to activated bone morphogenetic protein (BMP) signaling in denervated muscles, as indicated by the increased levels of phosphorylated Smad1/5/8. Our detailed evaluation of downstream genes of Myoparr also revealed that Myoparr regulated differential gene expression between myogenic differentiation and muscle atrophy. This is the first report demonstrating the in vivo role of Myoparr in regulating BMP signaling in denervated muscles. Therefore, lncRNAs that have inhibitory activity on BMP signaling may be putative therapeutic targets for skeletal muscle atrophy.