MAPT and Parkinson disease: A PSEN1 mutation causes a Pick’s disease phenotype including FTD tau pathology without deposition of Aβ [145]; some MAPT single nucleotide polymorphisms have also been linked to sporadic Parkinson’s disease (PD, [146]); and retarded axonal extension in tau-deficient hippocampal neurons may be due to reduced MT transport by lack of tau-mediated regulation of motor protein activities [147].