BACE1 and Alzheimer disease: Previous methylome profiling studies, however, on purified neural cell populations [95] as well as in hundreds of bulk brain tissue samples [107,108,109] of AD patients, did not bring conclusive evidence to support epigenetic dysregulation in the gene body and/or the promoter regions of other key AD genes involved in the formation of neurofibrillary tangles (GSK3B, MAPT) and regulating the production of Aβ peptide (BACE1, PSEN1, PSEN2).