To investigate the regulation of microglial Tmem9 in C1q‐mediated synapse engulfment, we treated the BV2 cells with oAβ or LPS (Lipopolysaccharides) + oAβ to establish the AD model in vitro and co‐cultured these BV2 cells with HT22 neuronal cells (Figure S3A). Here, TMEM9 is linked to Alzheimer disease.