The homeoprotein Msx1 plays a critical role in embryonic patterning, particularly to maintain myogenic progenitor cell fate. However, the mechanisms underlying Msx1-mediated inhibition of myogenesis remain largely unknown. Here, we show that Msx1 cooperates with the protein kinase C-related kinase 1 (Pkn1), a member of the protein kinase C-related kinase family, to prevent the terminal differentiation of myogenic precursor cells. In mouse C2C12 cells, Pkn1 knockout partly impaired Msx1-mediated inhibition of myogenic differentiation, indicating a role for Pkn1 in this process. Furthermore, we found that Pkn1 was required for Msx1 enrichment at the promoter of Myf5, a myogenic regulatory gene. In Pkn1 knockout cells, this reduced Msx1 enrichment at the Myf5 promoter coincided with attenuated repression of Myf5 transcription. Together with our observation that Msx1 and Pkn1 were associated in a protein complex, these findings strongly suggest that Msx1 cooperates with Pkn1 to down-regulate Myf5 and, therefore, prevent the differentiation of myogenic precursor cells. Collectively, our data provide key insights into the mechanisms underlying Msx1 function in the prevention of myogenic differentiation.

中文翻译：

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同源蛋白Msx1与Pkn1协同作用，以防止成肌前体细胞的终末分化。

同源蛋白Msx1在胚胎形成过程中起着至关重要的作用，特别是维持成肌祖细胞的命运。但是，Msx1介导的肌发生抑制的基本机制仍是未知之数。在这里，我们表明Msx1与蛋白激酶C相关激酶家族的成员蛋白激酶C相关激酶1（Pkn1）合作，以防止成肌前体细胞的终末分化。在小鼠C2C12细胞中，Pkn1敲除部分削弱了Msx1介导的肌原性分化抑制，表明Pkn1在此过程中发挥了作用。此外，我们发现Pkn1是Myf5（一种成肌调节基因）启动子上Msx1富集所必需的。在Pkn1基因敲除细胞中，这种在Myf5启动子处减少的Msx1富集与Myf5转录的减弱抑制相吻合。连同我们的观察结果，即Msx1和Pkn1在蛋白复合物中相关联，这些发现强烈表明Msx1与Pkn1协同下调Myf5，从而阻止了成肌前体细胞的分化。总的来说，我们的数据提供了对预防Msx1功能预防成肌分化的机制的关键见解。