Project description:MicroRNAs (miRNAs) are small noncoding RNAs that critically regulate gene expression. Their abundance and function have been linked to processes such as senescence and aging. In aged monkey muscle, miR-451a and miR-144-3p were highly upregulated compared to young animals. This led us to hypothesize that the miRNAs 451a/144-3p may be involved in muscle differentiation. We found that these miRNAs are downregulated during the differentiation of C2C12 myoblasts. Overexpression of miR-451a, but not miR-144-3p, robustly impeded the differentiation, suggesting an inhibitory role for miR-451a. We further investigated the potential regulatory targets of miR-451a and identified Sparc mRNA, encoding a secreted protein acidic and rich in cysteine (SPARC), which is involved in wound healing and cellular differentiation. Interestingly, we found that miR-451a suppresses Sparc mRNA translation according to the analysis of polysome profile. Our findings show that miR-451a is downregulated in differentiated myoblasts and decreases C2C12 differentiation at least in part by the suppression of SPARC biosynthesis.
Project description:MicroRNAs (miRNAs) are small noncoding RNAs that critically regulate gene expression. Their abundance and function have been linked to a range of physiologic and pathologic processes. In aged monkey muscle, miR-451a and miR-144-3p were far more abundant than in young monkey muscle. This observation led us to hypothesize that miR-451a and miR-144-3p may influence muscle homeostasis. To test if these conserved microRNAs were implicated in myogenesis, we investigated their function in the mouse myoblast line C2C12. The levels of both microRNAs declined with myogenesis; however, only overexpression of miR-451a, but not miR-144-3p, robustly impeded C2C12 differentiation, suggesting an inhibitory role for miR-451a in myogenesis. Further investigation of the regulatory influence of miR-451a identified as one of the major targets Sparc mRNA, which encodes a secreted protein acidic and rich in cysteine (SPARC) that functions in wound healing and cellular differentiation. In mouse myoblasts, miR-451a suppressed Sparc mRNA translation. Together, our findings indicate that miR-451a is downregulated in differentiated myoblasts and suggest that it decreases C2C12 differentiation at least in part by suppressing SPARC biosynthesis.
Project description:Myogenesis is a highly orchestrated process whereby muscle precursor cells, myoblasts, develop into muscle fibers to form skeletal muscle during embryogenesis and regenerate adult muscle. Here, we studied the RNA-binding protein FUS (fused in sarcoma), which has been implicated in muscular and neuromuscular pathologies but is poorly characterized in myogenesis. Given that FUS levels declined in human and mouse models of skeletal myogenesis, and that silencing FUS enhanced myogenesis, we hypothesized that FUS might be a repressor of myogenic differentiation. Interestingly, overexpression of FUS delayed myogenesis, accompanied by slower production of muscle differentiation markers. To identify the mechanisms through which FUS inhibits myogenesis, we uncovered RNA targets of FUS by ribonucleoprotein immunoprecipitation (RIP) followed by RNA-sequencing (RNA-seq) analysis. Stringent selection of the bound transcripts uncovered Tnnt1 mRNA, encoding troponin T (TNNT1), as a major effector of FUS influence on myogenesis. We found that in myoblasts, FUS sequestered Tnnt1 mRNA in the nucleus, preventing TNNT1 expression; however, reduction of FUS during myogenesis or by silencing FUS released Tnnt1 mRNA for export to the cytoplasm, where it accumulated and was translated into TNNT1, promoting myogenesis. We propose that FUS inhibits myogenesis by suppressing TNNT1 expression through a mechanism of nuclear mRNA retention.
Project description:Myogenesis is a highly orchestrated process whereby muscle precursor cells, myoblasts, develop into muscle fibers to form skeletal muscle during embryogenesis and regenerate adult muscle. Here, we studied the RNA-binding protein FUS (fused in sarcoma), which has been implicated in muscular and neuromuscular pathologies but is poorly characterized in myogenesis. Given that FUS levels declined in human and mouse models of skeletal myogenesis, and that silencing FUS enhanced myogenesis, we hypothesized that FUS might be a repressor of myogenic differentiation. Interestingly, overexpression of FUS delayed myogenesis, accompanied by slower production of muscle differentiation markers. To identify the mechanisms through which FUS inhibits myogenesis, we uncovered RNA targets of FUS by ribonucleoprotein immunoprecipitation (RIP) followed by RNA-sequencing (RNA-seq) analysis. Stringent selection of the bound transcripts uncovered Tnnt1 mRNA, encoding troponin T (TNNT1), as a major effector of FUS influence on myogenesis. We found that in myoblasts, FUS sequestered Tnnt1 mRNA in the nucleus, preventing TNNT1 expression; however, reduction of FUS during myogenesis or by silencing FUS released Tnnt1 mRNA for export to the cytoplasm, where it accumulated and was translated into TNNT1, promoting myogenesis. We propose that FUS inhibits myogenesis by suppressing TNNT1 expression through a mechanism of nuclear mRNA retention.
Project description:The mammalian RNA-binding protein AUF1 (AU-binding factor 1, also known as heterogeneous nuclear ribonucleoprotein D, hnRNP D) binds to numerous mRNAs and influences their post-transcriptional fate. Given that many AUF1 target mRNAs encode muscle-specific factors, we investigated the function of AUF1 in skeletal muscle differentiation. In mouse C2C12 myocytes, where AUF1 levels rise at the onset of myogenesis and remain elevated throughout myocyte differentiation into myotubes, RIP (RNP immunoprecipitation) analysis indicated that AUF1 binds prominently to Mef2c (myocyte enhancer factor 2c) mRNA, which encodes the key myogenic transcription factor Mef2c. By performing mRNA half-life measurements and polysome distribution analysis, we found that AUF1 associated with the 3’UTR of Mef2c mRNA and promoted Mef2c translation without affecting Mef2c mRNA stability. In addition, AUF1 promoted Mef2c gene transcription via a lesser-known role of AUF1 in transcriptional regulation. Importantly, lowering AUF1 delayed myogenesis, while ectopically restoring Mef2c expression levels partially rescued the impairment of myogenesis seen after reducing AUF1 levels. We propose that Mef2c is a key effector of the myogenesis program promoted by AUF1. Keywords: ribonucleoprotein complex; post-transcriptional gene regulation; muscle cell differentiation; myocytes; mRNA translation; mRNA stability; post-transcriptional gene regulation; transcriptome
Project description:The aim of this study was evaluate the transcriptome changes in the comparison between triple negative tumors with increased SPARC expression and triple negative tumors with decreased SPARC expression according to Nagai et al., 2011 (Breast Cancer Res Treat (2011) 126:1–14) The results generated could be of particular interest to better define the prognostic impact of SPARC expression in triple negative breast tumors
Project description:To filter the up-regulated gene induced by miR-451a overexpression and in cetuximab resistant HNSCC cell. We employed whole genome microarray. The HNSCC cell CAL27 was used as a control sample. CAL27_CTX, the cetuximab resistant CAL27 was compared with CAL27. The miR-451a overexpressed CAL27_451a sample was compared with the CAL27_NC sample. CAL27_CTX and CAL27_451A samples were collected after 48h of cetuximab treatment. The microarray results were taken together with ChIRP-seq analysis and bioinformatics analysis for miR-451a binding and enhancer analysis to eventually find the nuclear acticating target of miR-451a