MTHFD2 and myopathy: Upregulation of Methylenetetrahydrofolate dehydrogenase 2 (MTHFD2), an ATF4‐induced key enzyme of mitochondrial one carbon metabolism (Ben‐Sahra et al, 2016), was detected at the intermediate stage of myopathy and increased with age (23‐ and 38‐fold at 100 and 200 days, respectively, Fig 4D and E; Appendix Fig S4C and D).