MAPT and Alzheimer disease: R134d, a polyclonal antibodyraised against the longest human tau isoform, tau441 (Tatebayashi et al., 1999), detected smear bands in AD O-tau and ADbrain lysate but not in control brain lysates, confirming thetruncation and SDS- and β-mercaptoethanol-resistanthigh-molecular weight of AD O-tau (Figure 1B).