MAPT and frontotemporal dementia: Tauopathies can be further subdivided into primary tauopathies, in which tau is the main pathology-inducing molecule, such as frontotemporal dementia (FTD) [9], and secondary tauopathies, in which tau pathology occurs together with amyloid-β (Aβ) deposition, as exemplified by Alzheimer’s disease (AD) [10].