APOE (Hammond et al., 2019; Keren‐Shaul et al., 2017; Krasemann et al., 2017), APOC1(Hammond et al., 2019), and CTSD (Keren‐Shaul et al., 2017) were also signature genes in mouse models of neurodegenerative diseases (Keren‐Shaul et al., 2017; Krasemann et al., 2017) or aging (Hammond et al., 2019). This evidence concerns the gene CTSD and neurodegenerative disease.