MAPT and tauopathy: In a mouse model of tauopathy overexpressing a human Tau mutant known to be associated with frontotemporal dementia (R406W), constitutively active 5-HT7 receptors physically associated with Cdk5 induce hyperphosphorylation of Tau and the formation of highly bundled Tau structures48, suggesting that the 5-HT7 receptor–Cdk5 signaling pathway may be a new target in tauopathies.