MAPT and Alzheimer disease: Supporting that tau can spread from neuron to neuron trans-synaptically in humans, tau seeding activity was observed in brain regions composed of axons and synaptic fractions (DeVos et al. 2018), and oligomeric tau labeled with conformation-specific antibodies has been identified in presynaptic and postsynaptic terminals in AD brains even in regions that do not have extensive tangle pathology (Colom-Cadena et al. 2023).