APP and Alzheimer disease: Thus, DNA methylation studies at specific gene locus in postmortem brains (mixed-cell populations) [102,103] or analyzed by epigenome-wide association studies (EWAS) on sorted neuronal and non-neuronal (mostly glia) nuclei [95], revealed that reduced CpG methylation on the APP gene promoter in both neurons and glial cells in sporadic cases of AD accompanies increased APP gene expression (see Figure 4A).