Fig. 1
Chronic skin UV irradiation induced hippocampal memory deficit and transcriptomic changes associated with microglial function. A–D Experimental schedule of UV irradiation given 3 days a week for 6 weeks. After 5 weeks of UV irradiation, the object place recognition test was performed. B H&E staining. After 5 weeks of UV irradiation, the discrimination index was calculated as the difference between C, D the exploring time to novel place object (N) and familiar object (F), divided by the total time exploring both objects (discrimination index = (N − F)/(N + F).*P < 0.05 vs. control group. Each bar represents the mean ± SEM of each group. E–G Result of differentially expressed gene (DEG) analysis. E Volcano plot of UV-DEGs. Y axis refers to the adjusted p-values in − log10 scale. X axis refers to the mean expression ratio of UV-irradiated and control mice samples in log2 scale. The colors of the dots indicate the direction of regulation (red: up-regulation, blue: downregulation, gray: non-significant regulation). Adjusted p-values lower than 1.0 × 10–120 are displayed as 2.0 × 10–120 in the figure. Top 10 most downregulated DEGs are marked by larger points and labeled. F Functional annotations for UV-DEGs showing the top 15 significantly enriched gene ontology (GO) biological pathways. Top five UV-DEGs ranked by FDR overlapping with leading edge genes are shown, with letter colors indicating the direction of regulation (red: up-regulation, blue: downregulation). G Enrichment plot of microglia markers. X axis refers to the rank of genes in descending order of log2 fold change values. The vertical black lines on the X axis are the genes overlapping with the markers. The green line shows the cumulative enrichment score, calculated by walking down the gene list, where the score increases if a gene overlaps with the markers and decreases if a gene does not. The red dashed lines indicate the maximal and minimal scores. H Representative photographs of Iba-1+ cells in the hippocampal region. I The total number of Iba-1+ cells in the hippocampus were quantified in the graph. Each bar represents the mean ± SEM of each group. The asterisks denote a significant difference (**P < 0.01 vs. control group)