【Background】 Myogenesis occurs not only at the stage of embryonic development but also during muscle repair in adults. Recently discovered transmembrane protein Myomixer (Mymx) initiates myogenesis by executing cell-cell fusion, although the physiological significance of Mymx-dependent cell fusion on muscle cell differentiation is not yet clear. The current study aims to elucidate the role of Mymx on muscle cell gene expression to understand the physiological importance of cell-cell fusion on myogenesis.
【Material and Method】 C2C12 cells were used as in vitro myogenesis model of skeletal muscle cells. Mymx gene was knocked out in C2C12 cells (Mymx-KO) using CRISPR/Cas9. Mymx gene was rescued in Mymx-KO cells by retroviral gene transfer. Gene expression of Mymx-KO and rescued cells were analyzed by RNA-seq.
【Result】 We performed comparative transcriptome analysis to identify genes associated with Mymx mediated cell-cell fusion. For this, we compared Mymx-KO cells and Mymx-rescued cells. We found that the expression levels of genes related to myofibrils, EC coupling, and Ca²⁺ signaling were increased in Mymx-rescued cells after myogenic stimulation. Importantly, expression levels of myogenic transcription factors MyoD and myognenin were almost unaltered by the gene rescue of Mymx, suggesting that the Mymx-dependent gene expression is induced independently of these muscle-specific transcriptional regulators.
【Conclusion】 We found a novel linkage between Mymx expression and the expression of genes required for EC coupling.