MAPT and Alzheimer disease: Mutant tau molecules have been proven to cause neuronal death and dementia by blocking tau's ability to regulate microtubule instability.[37, 38, 39, 40, 41] In addition, in the brains of transgenic mice that overexpress mutant tau, as well as in the brains of humans with AD, mutant tau proteins are found to alter the functioning of nuclear pores involved in nucleocytoplasmic transport, which contributes to neurotoxicity.[29, 42]