MAPT and Alzheimer disease: Emerging synaptic targets: Synaptic loss assessed by PET using synaptic vesicle proteins 2A (SV2A) tracer [11C]UCB-J was recently reported in patients with primary tauopathies (Holland et al., 2020) and in AD (Coomans et al., 2021) where a link between tau [assessed by [18F]flortaucipir] and SV2A was detected.