Fig. 6

Cytoplasmic and mitochondrial accumulation of Polβ in 6-mo Tg mice hippocampal neurons. a Representative images of sagittal CA1 sections from 6-mo Wt and Tg mice hippocampi (n = 3 for each phenotype). The sections were co-labeled with anti-phospho-tau (AT8), and Polβ antibodies (n = 3 for each mouse category). Immunofluorescence signals were analyzed using laser scanning confocal microscopy (z projection). Nuclei were detected with DAPI staining. Representative nuclei are delimitated by white dashed lines. The scale bars represent 20 μm.. The intensity of the cellular and nuclear Polβ fluorescence signals was quantified within CA1 cells from 6-mo Wt and Tg hippocampi (cells: Wt, n = 64; Tg, n = 47; nuclei: Wt, n = 142; Tg, n = 88). Graph shows the mean of cellular or nuclear fluorescence per mouse category. Data are presented as mean ± SEM (*P < 0.05; **P < 0.01). The intensity of the cellular and nuclear Polβ fluorescence signals was separately quantified within CA1 cells from 6-mo Tg hippocampi with either high (High Ptau) or low phospho-tau (Low Ptau) levels (cells: Low Ptau n = 53, High PTau n = 27; nuclei Tg: Low Ptau n = 37, High PTau n = 47). Data are presented as mean ± SEM (*P < 0.05; **P < 0.01). The cut off value of fluorescence between high and low phospho-tau levels has been arbitrary chosen based on visual evaluation of the cytoplasmic phospho-tau labeling. b Mitochondrial localization of Polβ was assessed by labeling sagittal CA1 sections from 6-mo Wt and Tg mice with VDAC1 and Polβ antibodies (n = 3 for each mouse strain). Immunofluorescence signals were analyzed by laser scanning confocal microscopy (single confocal section). The scale bars represent 10 μm. Representative nuclei are delimitated by white dashed lines. White arrows point VDAC1 and Polβ co-localization. c Overlays of immunofluorescence labeling of VDAC1 and Polβ. d Representative immunoelectron microscopy images of CA1 sections from 6-mo Tg and Wt mice hippocampus. The sections were labeled with Polβ antibodies (n = 3 for each mouse strain). The scale bars represent 100 nm. Red arrows point Polβ localization. e Representative images of frontal cortex sections from human control (Ctr) and Braak VI Alzheimer frontal cortex (AD). The sections were labeled with the tau oligomer antibody, TOC1, and anti-Polβ antibody (n = 3 for each category). Immunofluorescence signals were analyzed by laser scanning confocal microscopy (z projection). Nuclei were detected with DAPI staining. Representative nuclei are delimitated by white dashed lines. The scale bars represent 20 μm. f Immunofluorescence labeling of the same sections with antibodies against Polβ and VDAC1 demonstrates mitochondrial localization of Polβ. Immunofluorescence signals were analyzed by laser scanning confocal microscopy (single confocal section). Nuclei were detected with DAPI staining. Representative nuclei are delimitated by white dashed lines. The scale bars represent 20 μm. White arrows point VDAC1 and Polβ localization