Biochemical and histochemical analysis of tau species in older compound and Trp73 mutant mice. A: Fluorescent immunostaining of a 85 day-old compound Tg Trp73+/- plus TgAPP+/- mouse hemizygous for the TgCRND8 transgene array (i-iv) with tau antibodies AT8, CP13, PHF1 and MC1. Decreasing amounts of somatodendritic staining are present with AT8, CP13 and PHF1 antibodies, respectively. Thread-like staining is not seen. Staining with MC1 (iv) may correspond to detection of blood vessels and a similar pattern was apparent with an anti-Aβ antibody 6E10 applied to a TgTauP301L mouse lacking an APP transgene (not shown). Panel v shows a section, processed in parallel, from a TgTauP301L mouse. Note that the panels i-iv were overexposed compared to panel v to demonstrate intensity differences between pathological features and neuroanatomical structures: a tangle bearing neuron is shown in the granular layer of the dentate gyrus (horizontal arrow) and glial plaques in the subiculum and molecular layer (vertical arrows). B: Western blot analyses of phospho-specific tau species in insoluble protein fractions derived from animals at 270 days of age. Tau antibodies, AT8 and AT180, (rows 1-2, respectively), were used. C: Insoluble tau fractions of brain homogenates prepared from a Trp73+/- mouse at age 17 months were examined by western blotting with antibodies as labeled. D: Histochemical analyses with AT8 and CP13 antibodies of a Trp73+/- mouse at age 17 months did not reveal tau immunostaining. Positive controls are as per Figure 2A. An age-matched wt mouse is also shown for these analyses of paraffin-embedded tissue. 4 x and 10 x objective was used for hippocampus and cortex, respectively. Loading controls in B and C were as per Figure 1.