PPP1R15A and neurodegenerative disease: Although GADD34 plays various roles without UPR signaling in some cells, such as cytokine production in dendritic cells, inhibition of apoptosis in liver cancer cells, and the response to chronic oxidative stress in neurodegenerative diseases (Clavarino et al, 2012; Goh et al, 2018; Song et al, 2019), the specific role of GADD34 in skeletal muscle has not been revealed.