The present findings following unilateral inoculation of sarkosyl-insoluble fractions of GGT into the hippocampus, together with the observations of previous studies, are consistent with the idea that tau can be transmitted trans-synaptically from one neuron to another neuron, and that this mechanism has implications in the progression of abnormal tau deposits in tauopathies [27, 49, 50, 79, 83, 106]. This evidence concerns the gene GGT1 and tauopathy.