Ppp1r1b-lncRNA inhibits PRC2 at myogenic regulatory genes to promote cardiac and skeletal muscle development in mouse and human

Lactate induces C2C12 myoblasts differentiation by mediating ROS/p38 MAPK signalling pathway

Lactate serves not merely as an energy substrate for skeletal muscle but also regulates myogenic differentiation, leading to an elevation of reactive oxygen species (ROS) levels. The present study was focused on exploring the effects of lactate and ROS/p38 MAPK in promoting C2C12 myoblasts differentiation. Our results demonstrated that lactate increased C2C12 myoblasts differentiation at a range of physiological concentrations, accompanied by enhanced ROS contents. We used n-acetylcysteine (NAC, a ROS scavenger) pretreatment and found that it delayed lactate-induced C2C12 myoblast differentiation by upregulating Myf5 expression on days 5 and 7 and lowering MyoD and MyoG expression. The finding implies that lactate accompanies ROS-dependent manner to promote C2C12 myoblast differentiation. Additionally, lactate significantly increased p38 MAPK phosphorylation to promote C2C12 cell differentiation, but pretreatment with SB203580 (p38 MAPK inhibitor) reduced lactate-induced C2C12 myoblasts differentiation. whereas lactate pretreatment with NAC inhibited p38 MAPK phosphorylation in C2C12 cells, demonstrating that lactate mediated ROS and regulated the p38 MAPK signalling pathway to promote C2C12 cell differentiation. In conclusion, our results suggest that the promotion of C2C12 myoblasts differentiation by lactate is dependent on ROS and the p38 MAPK signalling pathway. These observations reveal a beneficial role for lactate in increasing myogenesis through ROS-sensitive mechanisms as well as providing new ideas regarding the positive impact of ROS in improving the function of skeletal muscle.

Correlation between large rearrangements and patient phenotypes in NF1 deletion syndrome: an update and review

About 5-10% of neurofibromatosis type 1 (NF1) patients exhibit large genomic germline deletions that remove the NF1 gene and its flanking regions. The most frequent NF1 large deletion is 1.4 Mb, resulting from homologous recombination between two low copy repeats. This "type-1" deletion is associated with a severe clinical phenotype in NF1 patients, with several phenotypic manifestations including learning disability, a much earlier development of cutaneous neurofibromas, an increased tumour risk, and cardiovascular malformations. NF1 adjacent co-deleted genes could act as modifier loci for the specific clinical manifestations observed in deleted NF1 patients. Furthermore, other genetic modifiers (such as CNVs) not located at the NF1 locus could also modulate the phenotype observed in patients with large deletions. In this study, we analysed 22 NF1 deletion patients by genome-wide array-CGH with the aim (1) to correlate deletion length to observed phenotypic features and their severity in NF1 deletion syndrome, and (2) to identify whether the deletion phenotype could also be modulated by copy number variations elsewhere in the genome. We then review the role of co-deleted genes in the 1.4 Mb interval of type-1 deletions, and their possible implication in the main clinical features observed in this high-risk group of NF1 patients.

Identification of candidate regulatory genes for intramuscular fatty acid composition in pigs by transcriptome analysis

BACKGROUND

Intramuscular fat (IMF) content and its fatty acid (FA) composition are typically controlled by several genes, each with a small effect. In the current study, to pinpoint candidate genes and putative regulators involved in FA composition, we performed a multivariate integrative analysis between intramuscular FA and transcriptome profiles of porcine longissimus dorsi (LD) muscle. We also carried out a combination of network, regulatory impact factor (RIF), in silico prediction of putative target genes, and functional analyses to better support the biological relevance of our findings.

RESULTS

For this purpose, we used LD RNA-Seq and intramuscular FA composition profiles of 129 Iberian × Duroc backcrossed pigs. We identified 378 correlated variables (13 FA and 365 genes), including six FA (C20:4n-6, C18:2n-6, C20:3n-6, C18:1n-9, C18:0, and C16:1n-7) that were among the most interconnected variables in the predicted network. The detected FA-correlated genes include genes involved in lipid and/or carbohydrate metabolism or in regulation of IMF deposition (e.g., ADIPOQ, CHUK, CYCS, CYP4B1, DLD, ELOVL6, FBP1, G0S2, GCLC, HMGCR, IDH3A, LEP, LGALS12, LPIN1, PLIN1, PNPLA8, PPP1R1B, SDR16C5, SFRP5, SOD3, SNW1, and TFRC), meat quality (GALNT15, GOT1, MDH1, NEU3, PDHA1, SDHD, and UNC93A), and transport (e.g., EXOC7 and SLC44A2). Functional analysis highlighted 54 over-represented gene ontology terms, including well-known biological processes and pathways that regulate lipid and carbohydrate metabolism. RIF analysis suggested a pivotal role for six transcription factors (CARHSP1, LBX1, MAFA, PAX7, SIX5, and TADA2A) as putative regulators of gene expression and intramuscular FA composition. Based on in silico prediction, we identified putative target genes for these six regulators. Among these, TADA2A and CARHSP1 had extreme RIF scores and present novel regulators in pigs. In addition, the expression of TADA2A correlated (either positively or negatively) with C20:4n-6, C18:2n-6, C20:3n-6, C18:1n-9, and that of CARHSP1 correlated (positively) with the C16:1n-7 lipokine. We also found that these two transcription factors share target genes that are involved in lipid metabolism (e.g., GOT1, PLIN1, and TFRC).

CONCLUSIONS

This integrative analysis of muscle transcriptome and intramuscular FA profile revealed valuable information about key candidate genes and potential regulators for FA and lipid metabolism in pigs, among which some transcription factors are proposed to control gene expression and modulate FA composition differences.

Droplet Digital PCR for Fast and Accurate Characterization of NF1 Locus Deletions: Confirmation of the Predominant Maternal Origin of Type-1 Deletions

Neurofibromatosis type-1 is a genetic disorder caused by loss-of-function variants in the tumor-suppressor NF1. Approximately 4% to 11% of neurofibromatosis type-1 patients have a NF1 locus complete deletion resulting from nonallelic homologous recombination between low copy repeats. Codeleted genes probably account for the more severe phenotype observed in NF1-deleted patients. This genotype-phenotype correlation highlights the need for a detailed molecular description. A droplet digital PCR (ddPCR) set along the NF1 locus was designed to delimitate the three recurrent NF1 deletion breakpoints. The ddPCR was tested in 121 samples from nonrelated NF1-deleted patients. Classification based on ddPCR versus multiplex ligation-dependent probe amplification (MLPA) was compared. In addition, microsatellites were analyzed to identify parental origin of deletions. ddPCR identified 77 type-1 (64%), 20 type-2 (16%), 7 type-3 (6%), and 17 atypical deletions (14%). The results were comparable with MLPA, except for three atypical deletions misclassified as type-2 using MLPA, for which the SUZ12 gene was not deleted. A significant maternal bias (25 of 30) in the origin of deletions was identified. This study proposes a fast and efficient ddPCR quantification to allow fine NF1 deletion classification. It indicates that ddPCR can be implemented easily into routine diagnosis to complement the techniques dedicated to NF1 point variant identification. This new tool may help unravel the genetic basis conditioning phenotypic variability in NF1-deleted patients and offer tailored genetic counseling.

LncRNA12097.1 contributes to endometrial cell growth by enhancing YES1 activating β-catenin via sponging miR-145-5p

Despite previous investigations elucidating the regulatory mechanisms of long non-coding RNAs (lncRNAs) in endometrial function and reproductive disorders, the precise pathways through which lncRNAs impact endometrial functions and fertility remain unclear. In this study, we performed an expression profile analysis of lncRNAs in the endometrial tissue of Hu sheep with different prolificacy, identifying 13,707 lncRNAs. We discovered a bidirectional lncRNA, designated lncRNA12097.1, exhibiting significant up-regulation exclusively in the endometrium of Hu sheep with high fecundity. Functional analyses revealed lncRNA12097.1 significantly enhanced proliferation and cell cycle progression in both endometrial epithelial cell (EEC) and stromal cells (ESC), while inhibiting apoptosis in these cell types. Mechanistically, we demonstrated a directly interaction between lncRNA12097.1 and miR-145-5p, with YES proto-oncogene 1 (YES1) being identified as a validated target of miR-145-5p. Interference with lncRNA12097.1 resulted in suppressed cell growth through down-regulation of YES1 expression, which could be rescued by miR-145-5p. Furthermore, lncRNA12097.1 functions as a competitive endogenous RNA (ceRNA) for miR-145-5p in ESCs, sequestering miR-145-5p and preventing its binding to the 3'UTR of YES1 mRNA. This interaction led to increased expression of YES1 and subsequent activation of downstream β-catenin signaling, thereby promoting ESC growth in Hu sheep. These findings provide novel molecular insights into the mechanisms underlying prolificacy in sheep.

Mapping Chromatin Occupancy of Ppp1r1b-lncRNA Genome-Wide Using Chromatin Isolation by RNA Purification (ChIRP)-seq

Long non-coding RNA (lncRNA) mediated transcriptional regulation is increasingly recognized as an important gene regulatory mechanism during development and disease. LncRNAs are emerging as critical regulators of chromatin state; yet the nature and the extent of their interactions with chromatin remain to be fully revealed. We have previously identified Ppp1r1b-lncRNA as an essential epigenetic regulator of myogenic differentiation in cardiac and skeletal myocytes in mice and humans. We further demonstrated that Ppp1r1b-lncRNA function is mediated by the interaction with the chromatin-modifying complex polycomb repressive complex 2 (PRC2) at the promoter of myogenic differentiation transcription factors, TBX5 and MyoD1. Herein, we employed unbiased chromatin isolation by RNA purification (ChIRP) and high throughput sequencing to map the repertoire of Ppp1r1b-lncRNA chromatin occupancy genome-wide in the mouse muscle myoblast cell line. We uncovered a total of 99732 true peaks corresponding to Ppp1r1b-lncRNA binding sites at high confidence (p-value < 1E-5) and enrichment score ≥ 10). The Ppp1r1b-lncRNA-binding sites averaged 558 bp in length and were distributed widely within the coding and non-coding regions of the genome. Approximately 46% of these true peaks were mapped to gene elements, of which 1180 were mapped to experimentally validated promoter sequences. Importantly, the promoter-mapped binding sites were enriched in myogenic transcription factors and heart development while exhibiting focal interactions with known motifs of proximal promoters and transcription initiation by RNA Pol-II, including TATA-box, transcription initiator motif, CCAAT-box, and GC-box, supporting Ppp1r1b-lncRNA role in transcription initiation of myogenic regulators. Remarkably, nearly 40% of Ppp1r1b-lncRNA-binding sites mapped to gene introns were enriched with the Homeobox family of transcription factors and exhibited TA-rich motif sequences, suggesting potential motif-specific Ppp1r1b-lncRNA-bound introns. Lastly, more than 136521 enhancer sequences were detected in Ppp1r1b-lncRNA-occupancy sites at high confidence. Among these enhancers, 3390 (12%) exhibited cell type/tissue-specific enrichment in fetal heart and muscles. Together, our findings provide further insights into the genome-wide Ppp1r1b-lncRNA: Chromatin interactome that may dictate its function in myogenic differentiation and potentially other cellular and biological processes.

Mapping Chromatin Occupancy of Ppp1r1b-lncRNA Genome-Wide Using Chromatin Isolation by RNA Purification (ChIRP)-seq

Long non-coding RNA (lncRNA) mediated transcriptional regulation is increasingly recognized as an important gene regulatory mechanism during development and disease. LncRNAs are emerging as critical regulators of chromatin state; yet the nature and the extent of their interactions with chromatin remain to be fully revealed. We have previously identified Ppp1r1b-lncRNA as an essential epigenetic regulator of myogenic differentiation in cardiac and skeletal myocytes in mice and humans. We further demonstrated that Ppp1r1b-lncRNA function is mediated by the interaction with the chromatin-modifying complex polycomb repressive complex 2 (PRC2) at the promoter of myogenic differentiation transcription factors, TBX5 and MyoD1. Herein, we employed an unbiased chromatin isolation by RNA purification (ChIRP) and high throughput sequencing to map the repertoire of Ppp1r1b-lncRNA chromatin occupancy genome-wide in the mouse muscle myoblast cell line. We uncovered a total of 99732 true peaks corresponding to Ppp1r1b-lncRNA binding sites at high confidence (P-value < 1e-5 and enrichment score ≥ 10). The Ppp1r1b-lncRNA-binding sites averaged 558 bp in length and were distributed widely within the coding and non-coding regions of the genome. Approximately 46% of these true peaks were mapped to gene elements, of which 1180 were mapped to experimentally validated promoter sequences. Importantly, the promoter-mapped binding sites were enriched in myogenic transcription factors and heart development while exhibiting focal interactions with known motifs of proximal promoters and transcription initiation by RNA polII, including TATA, transcription initiator, CCAAT-box, and GC-box, supporting Ppp1r1b-lncRNA role in transcription initiation of myogenic regulators. Remarkably, nearly 40% of Ppp1r1b-lncRNA-binding sites mapped to gene introns, were enriched with the Homeobox family of transcription factors, and exhibited TA-rich motif sequences, suggesting potential motif specific Ppp1r1b-lncRNA-bound introns. Lastly, more than 136521enhancer sequences were detected in Ppp1r1b-lncRNA-occupancy sites at high confidence. Among these enhancers,12% exhibited cell type/tissue-specific enrichment in fetal heart and muscles. Together, our findings provide further insights into the genome-wide Ppp1r1b-lncRNA: Chromatin interactome that may potentially dictate its function in myogenic differentiation and potentially other cellular and biological processes.

Identification of long non-coding RNA in formaldehyde-induced cardiac dysplasia in rats

Formaldehyde exposure during pregnancy can cause fetal congenital heart disease (CHD). However, the regulatory mechanism remains unclear. Studies on the biology of long non-coding RNAs (lncRNAs) show that lncRNAs can influence cardiac development and disease. However, expression patterns and regulatory mechanisms of action of lncRNAs in formaldehyde-induced CHD remain unclear. We used high-throughput sequencing strategies as a means of identifying lncRNA expression profiles in heart tissues of normal and formaldehyde-exposed newborn rats. Overall, 763 differentially expressed lncRNAs were identified, including 325 and 438 that were respectively up-regulated and down-regulated. GO and KEGG analyses indicated that the Ras and hedgehog signaling pathways may be important regulatory pathways in CHD caused by exposure to formaldehyde. A lncRNA-miRNA-mRNA co-expression network was constructed and a key miRNA, rno-miR-665, was identified. Furthermore, qRT-PCR analysis verified that the novel lncRNAs: MSTRG.27313.2, MSTRG.30629.2, MSTRG.36520.33, MSTRG.91234.1, and MSTRG.91233.9, were upregulated in the formaldehyde-exposed group. These differentially expressed lncRNAs identified during formaldehyde-induced CHD in newborn rats help explain CHD pathogenesis and provide an effective reference for diagnosing and treating CHD.

LncRNA JPX targets SERCA2a to mitigate myocardial ischemia/reperfusion injury by binding to EZH2

BACKGROUND

Long non-coding RNAs (lncRNAs) are pivotal regulators in heart disease, including myocardial ischemia/reperfusion (I/R) injury. LncRNA just proximal to XIST (JPX) is a molecular switch for X-chromosome inactivation. Enhancer of zeste homolog 2 (EZH2) is a core catalytic subunit of the polycomb repressive complex 2 (PRC2), which is involved in chromatin compaction and gene repression. This study aims to explore the mechanism of JPX regulating the expression of Sarcoplasmic/endoplasmic reticulum Ca²⁺ ATPase 2a (SERCA2a) by binding to EZH2 and preventing cardiomyocyte I/R damage in vivo and in vitro.

METHODS

The adenovirus transfection technology was utilized before establishing the mouse myocardial I/R or HL1 cells hypoxia/reoxygenation injury model. Functional studies performed western blotting, qRT-PCR, ELISA, echocardiography, TTC-Evans blue staining, and TUNEL staining. Western blotting was used to determine the expression of EZH2, SERCA2a, anti-apoptosis protein Bcl2/Bax, cleaved-caspase 3/caspase 3, and cleaved-caspase 9/caspase 9. Fluorescence in situ hybridization (FISH) and native RNA immunoprecipitations (RIP) assays were employed to verify the interaction between JPX and EZH2. Chromatin immunoprecipitation (ChIP) assay was used to further explore the relationship between EZH2 and SERCA2a on the molecular level.

RESULTS

JPX overexpression alleviated cardiomyocyte apoptosis in vivo and in vitro, reduced the I/R-induced infarct size in mouse hearts, lowered the serum cTnI concentration, and promoted mouse cardiac systolic function. The evidence implies that JPX can alleviate I/R-induced acute cardiac damage. Mechanistically, the FISH and RIP assays showed that JPX could bind to EZH2. The ChIP assay revealed EZH2 enrichment at the promoter region of SERCA2a. Both the EZH2 and H3K27me3 levels at the promoter region of SERCA2a were reduced in the JPX overexpression group compared to those in the Ad-EGFP group (P < 0.01).

CONCLUSIONS

LncRNA JPX is directly bound to EZH2 and reduced the EZH2-mediated H3K27me3 in the SERCA2a promoter region, protecting the heart from acute myocardial I/R injury. Therefore, JPX might be a potential therapeutic target for I/R injury.

LncRNAs at the heart of development and disease

Long noncoding RNAs (LncRNAs) have emerged as a diverse class of functional molecules that contribute to nearly every facet of mammalian cardiac development and disease. Recent examples show that lncRNAs can be important co-regulators of cardiac patterning and morphogenesis and modulators of the pathogenic signaling that drives heart disease. The flexibility and chemical nature of RNA allows lncRNAs to utilize diverse mechanisms, mediating their effects through their sequence, structure, and molecular interactions with DNA, protein, and other RNAs. In vivo, i.e., animal, studies of individual lncRNAs highlight their ability to balance conserved cardiac gene expression networks, serve as specific and early biomarkers, and indicate their promise as useful therapeutic targets to treat human heart disease. Here, we review recent functionally characterized lncRNAs in cardiac biology and pathology and provide a perspective on emerging approaches to decipher the role of lncRNAs in the heart.

The control of polycomb repressive complexes by long noncoding RNAs

The polycomb repressive complexes 1 and 2 (PRCs; PRC1 and PRC2) are conserved histone-modifying enzymes that often function cooperatively to repress gene expression. The PRCs are regulated by long noncoding RNAs (lncRNAs) in complex ways. On the one hand, specific lncRNAs cause the PRCs to engage with chromatin and repress gene expression over genomic regions that can span megabases. On the other hand, the PRCs bind RNA with seemingly little sequence specificity, and at least in the case of PRC2, direct RNA-binding has the effect of inhibiting the enzyme. Thus, some RNAs appear to promote PRC activity, while others may inhibit it. The reasons behind this apparent dichotomy are unclear. The most potent PRC-activating lncRNAs associate with chromatin and are predominantly unspliced or harbor unusually long exons. Emerging data imply that these lncRNAs promote PRC activity through internal RNA sequence elements that arise and disappear rapidly in evolutionary time. These sequence elements may function by interacting with common subsets of RNA-binding proteins that recruit or stabilize PRCs on chromatin. This article is categorized under: RNA Interactions with Proteins and Other Molecules > Protein-RNA Recognition RNA Interactions with Proteins and Other Molecules > RNA-Protein Complexes RNA Interactions with Proteins and Other Molecules > Protein-RNA Interactions: Functional Implications.

Bioinformatic Tools for the Analysis and Prediction of ncRNA Interactions

Noncoding RNAs (ncRNAs) play prominent roles in the regulation of gene expression via their interactions with other biological molecules such as proteins and nucleic acids. Although much of our knowledge about how these ncRNAs operate in different biological processes has been obtained from experimental findings, computational biology can also clearly substantially boost this knowledge by suggesting possible novel interactions of these ncRNAs with other molecules. Computational predictions are thus used as an alternative source of new insights through a process of mutual enrichment because the information obtained through experiments continuously feeds through into computational methods. The results of these predictions in turn shed light on possible interactions that are subsequently validated experimentally. This review describes the latest advances in databases, bioinformatic tools, and new in silico strategies that allow the establishment or prediction of biological interactions of ncRNAs, particularly miRNAs and lncRNAs. The ncRNA species described in this work have a special emphasis on those found in humans, but information on ncRNA of other species is also included.

Multidimensional Mechanistic Spectrum of Long Non-coding RNAs in Heart Development and Disease

With the large-scale genome-wide sequencing, long non-coding RNAs (lncRNAs) have been found to compose of a large portion of the human transcriptome. Recent studies demonstrated the multidimensional functions of lncRNAs in heart development and disease. The subcellular localization of lncRNA is considered as a key factor that determines lncRNA function. Cytosolic lncRNAs mainly regulate mRNA stability, mRNA translation, miRNA processing and function, whereas nuclear lncRNAs epigenetically regulate chromatin remodeling, structure, and gene transcription. In this review, we summarize the molecular mechanisms of cytosolic and nuclear lncRNAs in heart development and disease separately, and emphasize the recent progress to dictate the crosstalk of cytosolic and nuclear lncRNAs in orchestrating the same biological process. Given the low evolutionary conservation of most lncRNAs, deeper understanding of human lncRNA will uncover a new layer of human regulatory mechanism underlying heart development and disease, and benefit the future clinical treatment for human heart disease.

Deletion of AT1a (Angiotensin II Type 1a) Receptor or Inhibition of Angiotensinogen Synthesis Attenuates Thoracic Aortopathies in Fibrillin1C1041G/+ Mice

Objective: A cardinal feature of Marfan syndrome is thoracic aortic aneurysm. The contribution of the renin-angiotensin system via AT1aR (Ang II [angiotensin II] receptor type 1a) to thoracic aortic aneurysm progression remains controversial because the beneficial effects of angiotensin receptor blockers have been ascribed to off-target effects. This study used genetic and pharmacological modes of attenuating angiotensin receptor and ligand, respectively, to determine their roles on thoracic aortic aneurysm in mice with fibrillin-1 haploinsufficiency (Fbn1C1041G/+). Approach and Results: Thoracic aortic aneurysm in Fbn1C1041G/+ mice was found to be strikingly sexual dimorphic. Males displayed aortic dilation over 12 months while aortic dilation in Fbn1C1041G/+ females did not differ significantly from wild-type mice. To determine the role of AT1aR, Fbn1C1041G/+ mice that were either +/+ or -/- for AT1aR were generated. AT1aR deletion reduced expansion of ascending aorta and aortic root diameter from 1 to 12 months of age in males. Medial thickening and elastin fragmentation were attenuated. An antisense oligonucleotide against angiotensinogen was administered to male Fbn1C1041G/+ mice to determine the effects of Ang II depletion. Antisense oligonucleotide against angiotensinogen administration attenuated dilation of the ascending aorta and aortic root and reduced extracellular remodeling. Aortic transcriptome analyses identified potential targets by which inhibition of the renin-angiotensin system reduced aortic dilation in Fbn1C1041G/+ mice. Conclusions: Deletion of AT1aR or inhibition of Ang II production exerted similar effects in attenuating pathologies in the proximal thoracic aorta of male Fbn1C1041G/+ mice. Inhibition of the renin-angiotensin system attenuated dysregulation of genes within the aorta related to pathology of Fbn1C1041G/+ mice.

Emerging Roles of LncRNAs in the EZH2-regulated Oncogenic Network

Cancer is a life-threatening disease, but cancer therapies based on epigenetic mechanisms have made great progress. Enhancer of zeste homolog 2 (EZH2) is the key catalytic component of Polycomb repressive complex 2 (PRC2) that mediates the tri-methylation of lysine 27 on histone 3 (H3K27me3), a well-recognized marker of transcriptional repression. Mounting evidence indicates that EZH2 is elevated in various cancers and associates with poor prognosis. In addition, many studies revealed that EZH2 is also involved in transcriptional repression dependent or independent of PRC2. Meanwhile, long non-coding RNAs (lncRNAs) have been reported to regulate numerous and diverse signaling pathways in oncogenesis. In this review, we firstly discuss functional interactions between EZH2 and lncRNAs that determine PRC2-dependent and -independent roles of EZH2. Secondly, we summarize the lncRNAs regulating EZH2 expression at transcription, post-transcription and post-translation levels. Thirdly, we review several oncogenic pathways cooperatively regulated by lncRNAs and EZH2, including the Wnt/β-catenin and p53 pathways. In conclusion, lncRNAs play a key role in the EZH2-regulated oncogenic network with many fertile directions to be explored.

Deciphering the chromatin organization and dynamics for muscle stem cell function

The chromatin landscape represents a critical regulatory layer for precise transcriptional control. Chromosome architecture restrains the physical access to the DNA elements and is one of the determinants that specifies cell identity. Adult stem cells possess the unique ability to differentiate into a specific lineage. One of the underexplored areas in skeletal muscle biology is the molecular mechanism guiding the chromatin organization changes in muscle stem cell specification, myogenic determination, and differentiation. In this review, we focus on the regulatory network guiding the progression of muscle stem cells to differentiated progeny. We summarize recent findings regarding the mechanisms directing myogenic cell fate decision and differentiation, with a particular focus on three-dimensional chromosome architecture and long noncoding RNA-associated chromatin accessibility changes.

The Key Lnc (RNA)s in Cardiac and Skeletal Muscle Development, Regeneration, and Disease

Non-coding RNAs (ncRNAs) play a key role in the regulation of transcriptional and epigenetic activity in mammalian cells. Comprehensive analysis of these ncRNAs has revealed sophisticated gene regulatory mechanisms which finely tune the proper gene output required for cellular homeostasis, proliferation, and differentiation. However, this elaborate circuitry has also made it vulnerable to perturbations that often result in disease. Among the many types of ncRNAs, long non-coding RNAs (lncRNAs) appear to have the most diverse mechanisms of action including competitive binding to miRNA targets, direct binding to mRNA, interactions with transcription factors, and facilitation of epigenetic modifications. Moreover, many lncRNAs display tissue-specific expression patterns suggesting an important regulatory role in organogenesis, yet the molecular mechanisms through which these molecules regulate cardiac and skeletal muscle development remains surprisingly limited. Given the structural and metabolic similarities of cardiac and skeletal muscle, it is likely that several lncRNAs expressed in both of these tissues have conserved functions in establishing the striated muscle phenotype. As many aspects of regeneration recapitulate development, understanding the role lncRNAs play in these processes may provide novel insights to improve regenerative therapeutic interventions in cardiac and skeletal muscle diseases. This review highlights key lncRNAs that function as regulators of development, regeneration, and disease in cardiac and skeletal muscle. Finally, we highlight lncRNAs encoded by imprinted genes in striated muscle and the contributions of these loci on the regulation of gene expression.

EZH2 as an epigenetic regulator of cardiovascular development and diseases

ABSTRACT

Enhancer of zeste homolog 2(EZH2) is an enzymatic subunit of polycomb repressive complex 2 (PRC2) and is responsible for catalyzing mono-, di-, and trimethylation of histone H3 at lysine-27(H3K27me1/2/3). Many noncoding RNAs or signaling pathways are involved in EZH2 functional alterations. This new epigenetic regulation of target genes is able to silence downstream gene expression and modify physiological and pathological processes in heart development, cardiomyocyte regeneration and cardiovascular diseases such as hypertrophy, ischemic heart diseases, atherosclerosis and cardiac fibrosis. Targeting the function of EZH2 could be a potential therapeutic approach for cardiovascular diseases.

Expression Profile of Long Noncoding RNAs and Circular RNAs in Mouse C3H10T1/2 Mesenchymal Stem Cells Undergoing Myogenic and Cardiomyogenic Differentiation

Background

Currently, a heterogeneous category of noncoding RNAs (ncRNA) that directly regulate the expression or function of protein-coding genes is shown to have an effect on the fate decision of stem cells. However, the detailed regulatory roles of ncRNAs in myogenic and cardiomyogenic differentiation of mouse C3H10T1/2 mesenchymal stem cells (MSCs) are far from clear.

Methods

In this study, 5-azacytidine- (5-AZA-) treated C3H10T1/2 cells were differentiated into myocyte-like and cardiomyocyte-like cells. Next, ncRNA associated with myogenic and cardiomyogenic differentiation was identified using high-throughput RNA sequencing (RNA-seq) data. Bioinformatics analysis was conducted to identify the differentially expressed ncRNAs and the related signaling pathways.

Results

Myotube-like structure was formed after 5-AZA treatment of C3H10T1/2 cells. In addition, myogenic and cardiomyogenic differentiation-related genes like GATA4, cTnt, MyoD, and Desmin were upregulated significantly after the 5-AZA treatment. Totally, 1538 differentially expressed lncRNAs and 3398 differentially expressed mRNAs were identified, including 1175 upregulated and 363 downregulated lncRNAs and 2429 upregulated and 969 downregulated mRNAs. In addition, 46 differentially expressed circRNAs were identified, including 25 upregulated and 21 downregulated circRNAs. Moreover, the differentially expressed mRNAs were enriched into 5 significant pathways, including those for focal adhesion, ECM-receptor interaction, PI3K-AKT signaling pathway, PPAR signaling pathway, and Tyrosine metabolism.

Conclusions

A systematic view of the expression of ncRNAs in myogenic and cardiomyogenic differentiation of MSCs was provided in the study.

Lnc-HZ08 regulates BPDE-induced trophoblast cell dysfunctions by promoting PI3K ubiquitin degradation and is associated with miscarriage

Increasing evidences have shown that pregnant women might miscarry after exposure with environmental BaP (benzo(a)pyrene). Additionally, BPDE (benzo(a)pyren-7,8-dihydrodiol-9,10-epoxide), the ultimate metabolite of BaP, could induce dysfunctions of human trophoblast cells. However, it is rarely correlated between miscarriage and trophoblast dysfunctions. Moreover, their underlying mechanisms are still largely unidentified. In this study, a novel lncRNA (long non-coding RNA), lnc-HZ08, was identified to be highly expressed in human recurrent miscarriage (RM) tissues and in BPDE-treated human trophoblast cells. Lnc-HZ08 acts as a RNA scaffold to interact with both PI3K and its ubiquitin ligase CBL (Cbl proto-oncogene), enhances their protein interactions, and promotes PI3K ubiquitin degradation. In RM tissues and BPDE-treated trophoblast cells, DNA methylation level in lnc-HZ08 promoter region was reduced, which promotes estrogen receptor 1 (ER)-mediated lnc-HZ08 transcription. Subsequently, this upregulated lnc-HZ08 downregulated PI3K level, suppressed PI3K/p-AKT/p-P21/CDK2 pathway, and thus weakened proliferation, migration, and invasion of human trophoblast cells, which further induces miscarriage. These results may provide novel scientific and clinical insights in the occurrence of unexplained miscarriage. A novel lncRNA (lnc-HZ08) regulates the functions of human trophoblast cells and affects miscarriage. Lnc-HZ08 promotes PI3K ubiquitin degradation by enhancing CBL and PI3K interactions, downregulates PI3K/p-AKT/p-P21/CDK2 pathway, and weakens proliferation, migration, and invasion of trophoblast cells. BPDE exposure reduces the DNA methylation level in lnc-HZ08 promoter region and promotes estrogen receptor 1 (ER)-mediated lnc-HZ08 transcription. The suppressed PI3K/p-AKT/p-P21/CDK2 pathway regulated by increased lnc-HZ08 is associated with miscarriage. These results provide novel insights in the occurrence of unexplained miscarriage. Graphical Headlights • Lnc-HZ08 downregulates PI3K/p-AKT/p-P21/CDK2 pathway to suppress proliferation, migration, and invasion of human trophoblast cells, and affects miscarriage. • Lnc-HZ08 acts as a RNA scaffold to enhance the protein interaction of PI3K and its ubiquitin ligase CBL, which increases PI3K ubiquitination and degradation. • Lnc-HZ08 transcription is associated with DNA methylation on its promoter region and transcription factor ER.

LncRNAs in Cardiomyocyte Maturation: New Window for Cardiac Regenerative Medicine

Cardiomyocyte (CM) maturation, which is characterized by structural, functional, and metabolic specializations, is the last phase of CM development that prepares the cells for efficient and forceful contraction throughout life. Over the past decades, CM maturation has gained increased attention due to the fact that pluripotent stem cell-derived CMs are structurally, transcriptionally, and functionally immature and embryonic-like, which causes a defect in cell replacement therapy. The current challenge is to discover and understand the molecular mechanisms, which control the CM maturation process. Currently, emerging shreds of evidence emphasize the role of long noncoding RNAs (lncRNAs) in regulating different aspects of CM maturation, including myofibril maturation, electrophysiology, and Ca²⁺ handling maturation, metabolic maturation and proliferation to hypertrophy transition. Here, we describe the structural and functional characteristics of mature CMs. Furthermore, this review highlights the lncRNAs as crucial regulators of different aspects in CM maturation, which have the potential to be used for mature CM production. With the current advances in oligonucleotide delivery; lncRNAs may serve as putative therapeutic targets to produce highly mature CMs for research and regenerative medicine.

lncRNA FDNCR promotes apoptosis of granulosa cells by targeting the miR-543-3p/DCN/TGF-β signaling pathway in Hu sheep

Long non-coding RNAs (lncRNAs) regulate the development of follicles and reproductive diseases, but the mechanisms by which lncRNAs regulate ovarian functions and fertility remain elusive. We profiled the expression of lncRNAs in ovarian tissues of Hu sheep with different prolificacy and identified 21,327 lncRNAs. Many of the lncRNAs were differentially expressed in different groups. We further characterized an lncRNA that was predominantly expressed in the ovaries of the low prolificacy Fec^B+ (LPB+) group and mainly present in granulosa cells (GCs), and the expression of this lncRNA decreased during follicular development, which we named follicular development-associated lncRNA (FDNCR). Next, we found that FDNCR directly binds miR-543-3p, and decorin (DCN) was identified as a target of miR-543-3p. FDNCR overexpression promoted GC apoptosis through increased expression of DCN, which could be attenuated by miR-543-3p. Furthermore, miR-543-3p increased and FDNCR reduced the expression of transforming growth factor-β (TGF-β) pathway-related genes, including TGF-β1 and inhibin beta A (INHBA), which were upregulated upon DCN silencing. Our results demonstrated that FDNCR sponges miR-543-3p in GCs and prevents miR-543-3p from binding to the DCN 3′ UTR, resulting in DCN transactivation and TGF-β pathway inhibition and promotion of GC apoptosis in Hu sheep. These findings provide insights into the mechanisms underlying prolificacy in sheep.

Long Non-Coding RNAs (lncRNAs) in Cardiovascular Disease Complication of Type 2 Diabetes

The discovery of non-coding RNAs (ncRNAs) has opened a new paradigm to use ncRNAs as biomarkers to detect disease progression. Long non-coding RNAs (lncRNA) have garnered the most attention due to their specific cell-origin and their existence in biological fluids. Type 2 diabetes patients will develop cardiovascular disease (CVD) complications, and CVD remains the top risk factor for mortality. Understanding the lncRNA roles in T2D and CVD conditions will allow the future use of lncRNAs to detect CVD complications before the symptoms appear. This review aimed to discuss the roles of lncRNAs in T2D and CVD conditions and their diagnostic potential as molecular biomarkers for CVD complications in T2D.

MicroRNA‑23a‑5p mediates the proliferation and differentiation of C2C12 myoblasts

Skeletal myogenesis is a highly ordered and complex biological process that is mediated by numerous regulatory factors. In previous studies, it has been demonstrated that microRNAs (miRs) and long non-coding RNAs (lncRNAs) serve key roles in skeletal myogenesis. The present study showed that the expression levels of miR-23a-5p showed a dynamic change from decrease to increase during C2C12 myoblast proliferation and differentiation. Functional analysis using 5-ethynyl-2′-deoxyuridine proliferation and Cell Counting Kit-8 detection assays indicated that overexpression of miR-23a-5p significantly promoted C2C12 myoblast proliferation compared with the negative control. In addition, in C2C12 myoblasts transfected with miR-23a-5p mimics, increased expression levels of regulators associated with cell proliferation (Cyclin E, CCND1 and Cyclin B) were observed compared with the negative control. By contrast, overexpression of miR-23a-5p decreased the expression levels of specific-myogenesis factors (MyoD, MyoG and Myf5) and decreased C2C12 myoblast differentiation. Luciferase activity assays indicated that miR-23a-5p suppressed the luciferase activity of lncDum. Further analysis demonstrated that miR-23a-5p not only showed an opposite expression level pattern compared with lncDum, which was first increased and then decreased, but also had an opposite effect on the proliferation and differentiation of C2C12 myoblasts compared with lncDum which inhibited cell proliferation and promoted cell differentiation. Taken together, these results indicated that miR-23a-5p may mediate the proliferation and differentiation of C2C12 myoblasts, which may be involved in lncDum regulation.