Circular RNA (circRNA) is a kind of novel endogenous noncoding RNA formed through back-splicing of mRNA precursor. The biogenesis, degradation, nucleus–cytoplasm transport, location, and even translation of circRNA are controlled by RNA-binding proteins (RBPs). Therefore, circRNAs and the chaperoned RBPs play critical roles in biological functions that significantly contribute to normal animal development and disease. In this review, we systematically characterize the possible molecular mechanism of circRNA–protein interactions, summarize the latest research on circRNA–protein interactions in muscle development and myocardial disease, and discuss the future application of circRNA in treating muscle diseases. Finally, we provide several valid prediction methods and experimental verification approaches. Our review reveals the significance of circRNAs and their protein chaperones and provides a reference for further study in this field.

Muscle is one of the most critical organs for mammals, which governs multiple movement and physiological functions. Circular RNA (circRNA) is a kind of novel endogenous RNA without 5'-Caps and 3'-poly(A) structures formed by pre-mRNA's back-splicing. RNA binding proteins (RBPs) control the production and degradation of circRNA, help nucleus-cytoplasm transport and locate circRNA, and regulate circRNA translation. Therefore, circRNAs and the chaperoned RBPs play critical roles in muscle growth, development, and disease progression. In this review, we systematically characterize the possible molecular mechanism of circRNA-protein interactions. Also, we summarize the latest researches on circRNA-protein interactions in muscle development and diseases. Besides, we provide several valid prediction methods and experimental verification approaches. Our review reveals the importance of circRNAs and their protein chaperones and provides a reference for further study in this field.

AbstractmiRNAs are well known to be gene repressors. A newly identified class of miRNAs termed nuclear activating miRNAs (NamiRNAs), transcribed from miRNA loci that exhibit enhancer features, promote gene expression via binding to the promoter and enhancer marker regions of the target genes. Meanwhile, activated enhancers produce endogenous non-coding RNAs (named enhancer RNAs, eRNAs) to activate gene expression. During chromatin looping, transcribed eRNAs interact with NamiRNAs through enhancer-promoter interaction to perform similar functions. Here, we review the functional differences and similarities between eRNAs and NamiRNAs in myogenesis and disease. We also propose models demonstrating their mutual mechanism and function. We conclude that eRNAs are active molecules, transcriptional regulators, and partners of NamiRNAs, rather than mere RNAs produced during enhancer activation.

Myogenesis is a complex process controlled by several coding and non-coding RNAs (ncRNAs), such as circular RNAs (circRNAs) that are known to function as endogenous microRNAs (miRNAs) sponges. Cerebellar Degeneration-Related protein 1 antisense (CDR1as) is the most spotlighted circRNA that is known as an miR-7 sponge, which has bloomed circRNAs’ research in animal disease and physiology. Here, we screened for miRNAs and mRNA associated with CDR1as and further characterized their regulatory function during muscle differentiation. We found that a total of 43 miRNAs (including miR-107-3p, miR-125b-5p, miR-140-5p, miR-29a-3p, and miR-27a-3p upregulated) and 789 mRNAs (including ANGPT1, E2F2, CCN1, FGFR1, and MEF2C downregulated) were differentially expressed in goat skeletal muscle satellite cells (SMSCs). Further, knockdown of CDR1as and ANGPT1 inhibited SMSCs differentiation. miR-27a-3p was differentially upregulated after the knockdown of CDR1as in SMSCs. Overexpressed miR-27a-3p decreased SMSCs differentiation. Via RNAhybrid and luciferase, miR-27a-3p was identified to regulate ANGPT1. We discovered that miR-27a-3p has an inverse relationship with CDR1as and decreases the expression level of ANGPT1 during SMSCs differentiation. In summary, our study demonstrates that siCDR1as inhibits myoblast differentiation by downregulating ANGPT1 mRNA via miR-27a-3p in SMSCs.

Changes in climatic conditions are associated with changes in the physicochemical properties of many fruits. Four germplasms of cashew apple originating from Brazil, Tanzania, Ghana (herein referred to as local) and Mozambique but all grown in Ghana were studied to assess the effect of agro-climatic zones on the sugar accumulation, pH, and weight of these cashew apples. Cashew apples were sourced from experimental stations in Bole and Wenchi in the Northern and Savannah regions of Ghana, respectively. A total of 1800 fruits were used for the experiment. Inter and intra significant differences (P < 0.05) were scored amongst ger­mplasms collected from both locations concerning the measured parameters. Sugar ranged between 8.7% - 12.5% with fruits from Bole having the highest sugar content. The pH value ranged from 3.9 (Local germplasm from Bole) – 4.3 (Tanzania germplasm from both loca­tions). The weight ranged between 33 g (Tanzania germplasm from Bole) – 69.8 g (Brazil germplasm from Bole). Meteorological data (from February 2017- April 2018) collected from both locations inf‍luenced the parameters, thus associating with the fruits from both locations. Conclusively, the present study indicated that, weather and geographical locations had an effect on sugar content, pH, and weight of cashew apples.

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Background: Myogenesis is a complex process controlled by several coding and non-coding RNAs (ncRNAs) such as circular RNAs (circRNAs) that well-known function as endogenous microRNAs (miRNAs) sponges. Over the past few years, numerous circRNAs have been known and their roles in biological processes have begun to be understood. Cerebellar Degeneration-Related protein 1 antisense (CDR1as), the most spotlighted circRNA as miR-7 sponge that has been blooming circRNAs’ research for a decade, and can potentially sponge several miRNAs in disease and muscle physiology. Nevertheless, the linear-RNAs-differed character that the acute interventions for circRNAs do not affect miRNAs levels, and has retarded the transcriptome-wide discovery of miRNAs sponged by. Therefore, the purpose of this study was to provide the transcriptomic effect of CDR1as during muscle differentiation.Methods: siCDR1as and siDICER1 were transfected into goat skeletal muscle satellite cells (SMSCs). RNA-seq technology and bioinformatics tools were used to analyze genes that are deregulated by siCDR1as and siDICER1. quantitative PCR was used to verify the expression levels of the differentially expressed mRNAs and miRNAs. Results: Here, to systematically identify miRNAs targeting CDR1as, we employed the critical enzyme DICER1 that governs the biogenesis of miRNAs. The deficiency of either DICER1 or CDR1as inhibited myogenic differentiation of SMSCs, and knockdown of DICER1 decreased the expression of CDR1as. Moreover, we screened for the targeted messenger RNAs (mRNAs) and miRNAs in SMSCs transfected with siDICER1 or siCDR1as respectively and found out that some well-known muscle-related pathways such as phosphoinositide 3-kinase (PI3K)-AKT signaling pathway, Rap1 signaling pathway, and MAPK signaling pathway were enriched in all groups. Further, regarding the miRNAs identified in siDICER1 and siCDR1as together with the sequence complementary information, we identified 11 miRNAs including miR-1, miR-206, and miR-27a-5p which are more likely to be novel targets for CDR1as. Conclusion: In summary, our study provides a perspective on the potential functions and relationship between CDR1as and DICER1 during muscle development.