The proliferation of microglia in prion disease is regulated by the activation of CSF1R and the transcription factors PU.1 and CCAAT/enhancer-binding protein alpha (C/EBPα, being this system also active in human variant CJD and Alzheimer’s disease (AD; Gómez-Nicola et al., 2013; Olmos-Alonso et al., 2016). This evidence concerns the gene SPI1 and Alzheimer disease.