MAPT and semantic dementia: To investigate the interaction of LRRK2 and tau in a mammalian system, we used transgenic mice expressing FTDP-17-associated P301L mutant human tau in the forebrain via a calcium/calmodulin-dependent protein kinase II reverse transactivator (CAMKIIα-tTA) transgene [48] crossed to wild-type LRRK2 bacterial artificial chromosome (BAC) transgenic mice.