SELENON and myopathy: As shown by ERO1-injected SEPN1 KO mice and the compound DKO mice fed on the medium dose of ascorbic acid, the pathological cause of SEPN1-related myopathies is not primarily due to the TGF-beta-dependent fibrosis (only seen in DKO mice fed on the low dose), but to a TGF-beta-dependent functional defect in muscle fibers that affects muscle strength.