C9orf72 and amyotrophic lateral sclerosis: GSK3β is a negative regulator of the VAPB-PTPIP51 interaction and its activation has been linked to disruption of ER-mitochondria tethering and signaling by ALS mutant TDP43, FUS, and C9orf72 in experimental models (Stoica et al., 2014; Stoica et al., 2016; Gomez-Suaga et al., 2022).