Non cell-autonomous mechanisms may contribute to tau pathology progression outside of the hippocampal formation.

<p>Frozen mouse brain sections (10 μm) were subjected to Immuno-FISH as described in the Materials and Methods. Human tau mRNA was labeled with a specific RNA probe (green), and human tau protein was visualized using Tau13 antibody (magenta). The nuclei were counterstained with Hoechst 33342. Z-stack images were taken using an LSM700 confocal microscope. Some cells were identified (white circles or ovals) in most brain regions along the entorhinal cortex-hippocampus circuit, parahippocampal regions and the cortex that were human tau protein positive but human tau mRNA negative. MEC, medial entorhinal cortex; LEC, lateral entorhinal cortex; DG, dentate gyrus; CA, Cornu ammonis; PaS, parasubiculum; PrS, presubiculum; Sub, subiculum; Prh, perirhinal cortex; AM, amygdala. Scale bar = 40 μm.