Immuno-FISH for huTau mRNA (green) and phospho-tau (PHF1, red) shows obvious differences in the distribution of neurons in cortex layer II/III: 9-month-old rTg4510 mice had more neurons filled with NFT-like phosphorylated tau (PHF1+, red), and rTg4510-Mapt0/0 mice had significantly more huTau mRNA positive neurons (FISH+). rTg4510-Mapt0/0 mice had also more neurons still expressing both PHF1 and huTau mRNA (PHF1+ FISH+), suggesting a reduced neurotoxicity of P301Ltau expression in rTg4510-Mapt0/0 mice. Mean±SEM, n=3 sections per mouse, 3 mice/group. For all panels: two-tailed Student's T-test and one-way ANOVA with Bonferroni for multiple comparison, ns not significant, scale bars 100 μm. 