MAP2 and Alzheimer disease: Conformationally altered tau, which could be detected by MC1 antibody in rat,26 is another critical intermediate state for pathological aggregation of tau protein seen only in AD but not healthy control brains.53 We observed MC1-positive immunofluorescence in MAP2 labeled hippocampus CA1 neurons in 22-month-old homozygous AppNL-G-F rats and 12-month-old 3× Tg-AD mice, but not WT control rats (Fig. 2i).