CTSD and amyotrophic lateral sclerosis: Several of these genes were also associated with microglial activation and neurodegenerative disorders (CTSD, SPP1, CPM and APOE) (Fig. 6c,d) and interestingly with ALS–FTD (TREM2, OPTN, SQSTM1/p62 and GRN) (Fig. 5e,f).