To define whether the reduced size of the Sam68−/− fibers is accompanied by features of atrophy (Bonaldo & Sandri, 2013), we analyzed the expression levels of two atrophy-related genes: the ubiquitin ligases Fbxo32 (MAFbx/atrogin-1) and Trim63 (muscle RING-finger 1, MuRF1). This evidence concerns the gene TRIM63 and Atrophy.