C9orf72 ALS/FTD iPSC-MG can be used in a 2- or 3-dimensional co-culture system or can be transplanted in vivo into mouse models to further assess the microglial contribution to neuronal dysfunction and degeneration in C9orf72 ALS/FTD (Abud et al., 2017; Xu et al., 2020). Here, C9orf72 is linked to frontotemporal dementia.