MAPT and early-onset autosomal dominant Alzheimer disease: Using a transgenic mouse that conditionally expresses tau in the area of the brain where Alzheimer’s disease pathology first arises—the entorhinal cortex—researchers have shown that tau appears to spread between synaptically connected brain regions, suggesting a potential role of the synapse in pathological tau transport (de Calignon et al., 2012; Liu et al., 2012).