PRMT5 links lipid metabolism to contractile function of skeletal muscles

The skeletal muscle plays a key role in systemic energy homeostasis besides its canonical contractile function, but what couples these functions is poorly defined. Protein Arginine MethylTransferase 5 (PRMT5) is a well-known oncoprotein but also expressed in healthy tissues with unclear physiological functions. As adult muscles express high levels ofPrmt5, we generated myocyte-specificPrmt5knockout (Prmt5^MKO) mice. We observed reduced muscle mass, oxidative capacity, force production and exercise performance inPrmt5^MKOmice. The motor deficiency is associated with scarce lipid droplets in myofibers due to defects in lipid biosynthesis and degradation. First,Prmt5^MKOreduced demethylation and stability of Sterol Regulatory Element-Binding Transcription Factor 1a (SREBP1a), a master regulator ofde novolipogenesis. Second,Prmt5^MKOimpaired the repressive H4R3Me2s (histone H4 arginine-3 symmetric demethylation) at thePnpla2gene, elevating the level of its encoded protein ATGL, the rate-limiting enzyme catalyzing lipolysis. Accordingly, myocyte-specific double knockout ofPnpla2andPrmt5normalized muscle mass and function. Together, our findings delineate a physiological function of PRMT5 in linking lipid metabolism to contractile function of myofibers.