MAPT and Alzheimer disease: Furthermore, co-immunostaining of SUMO1 with HT7 (total tau) or AT180 (pT231) antibodies revealed a robust colocalization of SUMO1 with tau species in the hippocampi of AD patients (Fig. 11M-P), which is in agreement with the immunoprecipitation data and supports the presence of aberrantly upregulated tau SUMOylation in AD.