For example, even with DUX4 at barely detectible levels, FSHD myoblasts are highly sensitive to oxidative stress (20,43–45), and we have shown previously that PAX7 target gene repression is associated with up-regulation of HIF1α and an oversensitivity to oxidative stress (19,28). This evidence concerns the gene DUX4 and facioscapulohumeral muscular dystrophy.