Ectopic expression of IRE1 or its downstream effector Xbp1s, as well as pharmacological activation of IRE1 using IXA4, significantly reduces poly(GR) protein levels in a Drosophila disease model, mammalian cell lines, fibroblasts derived from patients with C9orf72-ALS, and a C9orf72 transgenic mouse model. Here, C9orf72 is linked to amyotrophic lateral sclerosis.