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. 2024 Mar 6;20(4):2843–2860. doi: 10.1002/alz.13737

FIGURE 3.

FIGURE 3

Aggregation of pT217‐tau along microtubules in dendritic shafts. ImmunoEM demonstrates aggregation of pT217‐tau along dendritic microtubules in putative excitatory cells in “early” aged (18–24 years) macaque ERC layer II (A‐B) and pyramidal cells in “late” aged (26–31 years) macaque dlPFC layer III (C‐D). Ultrastructural examination revealed dense accumulation of pT217‐tau occurring in parallel microtubule bundles in horizontal dendrites. Red arrowheads point to pT217‐tau immunoreactivity. Profiles are pseudocolored for clarity. Scale bars, 200 nm. Quantitative analysis of pT217‐tau immunoEM localization in rhesus macaque “early” aged (18–24 years) ERC layer II circuits (E). The prevalence of pT217‐tau in various cellular subcompartments in layer II of the ERC neuropil, expressed as percentage of pT217‐tau profile (e.g., dendrite) per total pT217‐tau profiles. We analyzed a total of 1205 pT217‐tau immunopositive profiles in “early” aged (18–24 years) ERC layer II neuropil. pT217‐tau is primarily expressed in postsynaptic subcompartments in “early” aged (18–24 years) ERC layer II microcircuits, with foremost expression in dendritic shafts, and significant expression within dendritic spines. Quantitative analysis of pT217‐tau immunoEM localization in rhesus macaque in “late” aged (26–31 years) macaque dlPFC layer III (F). The prevalence of pT217‐tau in various cellular subcompartments in layer III of the dlPFC neuropil, expressed as percentage of pT217‐tau profile (e.g., dendritic shaft) per total pT217‐tau profiles. We analyzed a total of 1254 pT217‐tau immunopositive profiles in “late” aged (26–31 years) macaque dlPFC layer III. pT217‐tau is primarily expressed in postsynaptic subcompartments in dlPFC layer III microcircuits, with greatest expression in dendritic shafts, and significant expression within dendritic spines. For additional details regarding quantitative assessment and profile identification see Materials and Methods section. Nondetermined (N.D) are profiles that could not be unequivocally categorized. Den, dendrite; dlPFC, dorsolateral prefrontal cortex; ERC, entorhinal cortex; Mit, mitochondria; pT217‐tau, tau phosphorylated at threonine‐217