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Fig. 5 | Acta Neuropathologica Communications

Fig. 5

From: Hippocampal tau oligomerization early in tau pathology coincides with a transient alteration of mitochondrial homeostasis and DNA repair in a mouse model of tauopathy

Fig. 5

Increased levels of BER activity, 8-oxo-G base lesion, and OGG1 DNA glycosylase in CA1 neurons in 6-mo Tg mice. Biochemical analysis of BER activity in CA1 extracts from 6-mo Tg and Wt mice. a AP-site incision activity. Recombinant APE1 protein was used as a positive control. b Uracil removal activity. Purified recombinant UNG was used as a positive control. c 8-oxo-dG removal activity. Formamidopyrimidine DNA glycosylase (FPG) was used as a positive control. d Polβ nucleotide incorporation activity. e Quantifications of A-D, data are presented as mean ± SEM (*P < 0.05). WB analysis of CA1 extracts from 6-mo Wt (n = 5) and Tg (n = 6) mice (f), and hippocampus extracts from 12-mo Wt (n = 5) and Tg (n = 5) mice (g) for OGG1. Actin was used as a loading control. Quantification results are shown in the graph below. Data are presented as mean ± SEM (***P < 0.001). h Representative images of sagittal CA1 sections from 6-mo Wt and Tg mice. The sections were co-labeled with AT8 and anti-OGG1 antibodies (n = 3 for each mouse strain). The immunofluorescence signals were analyzed by laser scanning confocal microscopy (z projection). DAPI staining was used to visualize nuclei. Representative nuclei are delimitated by white dashed lines. The scale bars represent 20 μm. The cellular and nuclear OGG1 fluorescence intensity was quantified within CA1 cells (cells: Wt, n = 18; Tg, n = 18)(nuclei: Wt, n = 68; Tg, n = 116). Graph shows the mean of cellular or nuclear fluorescence per mouse category. Data are presented as mean ± SEM (**P < 0.01). i Possible mitochondrial localization of OGG1 was determined by labeling sagittal CA1 sections from 6-mo Wt and Tg mice with anti-VDAC1 and anti-OGG1 antibodies (n = 3 for each mouse strain). Immunofluorescence labeling was analyzed using laser scanning confocal microscopy (single confocal section). DAPI staining was used to visualize nuclei. The scale bars represent 20 μm. Representative nuclei are delimitated by white dashed lines. The scale bars represent 10 μm. j Overlay of VDAC1 and OGG1 Immunofluorescence signals. The scale bars represent 20 μm. k Representative images of sagittal CA1 sections from 6-mo Wt and Tg mice hippocampi (n = 3 for each mouse strain). The sections were labeled with the 8-oxo-G antibody after RNAse pretreatment as described before [84] to selectively target oxidative DNA lesions (8-oxo-G). 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 nuclear 8-oxo-G fluorescence signals was quantified within CA1 cells from 6-mo Wt and Tg hippocampi (nuclei: 6-mo Wt, n = 98; 6-mo Tg, n = 343). Graph shows the mean of cellular or nuclear fluorescence per mouse category. Data are presented as mean ± SEM (***P < 0.001). S, substrate; P, repair product

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