MAPT and Alzheimer disease: Tau is one of the main proteins involved in AD, and the phosphorylated epitopes of the nuclear tau appear to have a central role in aging and at the onset of AD, possibly due to its specific location in the nucleus where it may regulate the transcriptional activity of the nucleolus, as recently described in both human neurons from CA1 region of the hippocampus, and human neuroblastoma SK-N-BE cell line [17,20,22], following several other data on nuclear tau interaction with chromatin [15,16,18,26].