YFP-expressing layer V neurons are free of hyperphosphorylated tau. a-a” Immunohistochemical labeling of human tau (antibody HT7, magenta, a) in the somatosensory cortex of a 4-month-old P301S Tau x YFP-H mouse. One cell filled with densely accumulated somatodendritic tau is marked by an asterix. YFP-expressing layer V pyramidal neurons (green, a’) bearing the tau transgene show white cytosol labeling on the merged image (a”; inset). b-b” Staining of hyperphosphorylated tau (antibody AT8, magenta, b) in the somatosensory cortex of a 4-month-old P301S Tau x YFP-H mouse revealed only very few YFP-expressing layer V neurons (green; b’) to contain AT8-positive tau (white cell in b”). c-d Pie charts of the fractions of YFP-expressing (YFP+) layer V neurons containing (AT8+) or lacking (AT8-) AT8-positive hyperphosphorylated tau in 4- (c) and 6-month-old (d) P301S Tau mice. Presented are means ± SD of 5–6 mice per group; 1983–2433 cells in 0.32-0.39 mm3 tissue. a-a” and b-b” show maximum intensity projections of 50 μm z-stacks. Scale bars: 50 μm; inset: 30 μm.