Fig. 4

Trem2 deletion enhances interneuronal tau transduction. A Schematic representation of a microglia-mediated interneuronal tau transduction system using a microfluidic 3-chamber culture system (left); a representative 3-chamber culture setup is shown (right). WT murine neurons are cultured in first and 3rd layers (Layers 1 and 3) (tubulin, red), and WT or Trem2 KO microglia (Iba1, purple) are cultured in the intermediary chamber (Layer 2). AAV-P301L tau is transduced in the first layer, and effects of microglia in intermediary Layer 2 are determined on transmission of tau into neuronal Layer 3 by staining for human tau. B Neurons are exposed to 1 × 10¹⁰ VP/ml AAV-P301L tau in Layer 1, and transduction of P301L tau from Layer 1 into Layers 2 (microglia) and 3 (neurons) is quantified following transduction in the presence of WT or Trem2 KO microglia, or without microglia in intermediary Layer 2 as indicated. Fluorescence imaging was used to characterize neuronal processes (tubulin, red), recombinant tau (h-tau, green), and microglia (Iba1). C Fluorescence intensity of human tau, tubulin, and neuronal numbers quantified in Layers 1 and 3, and quantification of microglia (Iba1) and Iba1/tau overlap in Layer 2. Graph depicts mean ± SE of 3 independent experiments (individual plots), averaged from 3 replicates per experiment. Statistical significance was determined by One-way ANOVA, with Tukey’s multiple comparison (*p < 0.05, **p < 0.01, ***p < 0.001)