Résumé :
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MicroRNAs (miRNAs) are key molecules in cell biology. Here, we used a genome-wide miRNA loss-of-function screen based on LNA antisense oligonucleotides in order to identify miRNAs that are essential for terminal differentiation of human skeletal muscle cells. As much as 77 miRNAs were scored as hits. Most of the hits were not detected as differentially expressed in expression screens. A variety of phenotypes were observed such as inhibition of differentiation, inhibition of differentiation with poor cell survival or, on the contrary, increased cell proliferation. We also observed, precocious differentiation and myotube hypertrophy. The vast majority of the hits were confirmed in a secondary screen and, most of them were validated by gain-of-function assays. In order to identify the cellular pathways on which hit miRNAs are impacting, we used a suppressor screen (concomitant knockdown of miRNA and target protein). This assay led the identification of novel controllers of muscle cell terminal differentiation and novel key cellular pathways, some of which are interconnected. Thus, our miRNA systematic knockdown combined with gene co-suppression assays proved to be a powerful tool to decipher the highly complex process of muscle cell differentiation.
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