MAPT and early-onset autosomal dominant Alzheimer disease: For Alzheimer’s disease, the idea of a possible transmission of tau from the locus coeruleus to the transentorhinal cortex via neuron-to-neuron transmission and transsynaptic transport has been proposed after the observation of pretangles within noradrenergic coeruleus projection neurons in the absence of any pathology in the medial temporal lobe [176, 177].