However, since C9orf72 knockout mice failed to display an ALS/FTD-related motor neuron disease phenotype (Lagier-Tourenne et al., 2013; Koppers et al., 2015; Atanasio et al., 2016; McCauley et al., 2020), this option is rather unlikely. This evidence concerns the gene C9orf72 and frontotemporal dementia.