Involvement of miR-129-5p in the regulation of CD200R1 expression.A, in silico analysis using TargetScan and RNAhybrid predicted the two putative miR-129-5p binding sites (277–297 bases and 321–338 bases) in the 3′UTR of mouse CD200R1 mRNA. B, in vitro arsenic exposure increased the level of miR-129-5p in neonatal microglia (n = 3); (C) similar increase was observed in ex vivo microglia following in vivo arsenic exposure (n = 3 mice/group). D, in vitro transfection of pre-miR-129 for 72 h reduced the expression of CD200R1 (n = 3); (E) whereas anti-miR-129 transfection increased the expression of CD200R1 (n = 3); (F) Microglia were treated with arsenic followed by anti-miR-129 transfection showed reversal effect of arsenic on CD200R1 expression (n = 3). G, in silico analysis also predicted two putative miR-129-5p binding sites (1607–1634 bases and 2047–2072 bases) in the 3′UTR of human CD200R1 mRNA. Reduction in CD200R1 expression was observed in CHME3 cells following (H) in vitro transfection of pre-miR-129 (n = 4) and (I) in vitro arsenic exposure for 72 h (n = 4). J, immunostaining of human CD200R1 showed reduced immunoreactivity following pre-miR-129 and arsenic treatment. Scale bar: 15 μm for uncropped images and 5 μm for the cropped images. K, in vitro arsenic exposure increased the level of miR-129-5p in CHME3 cells. “n” denotes the number of independent study for in vitro experiments. Bar graphs represent mean ± SEM. “p” denotes the level of significance in comparison to control; ∗p < 0.05, ∗∗p < 0.01, ∗∗∗p < 0.001; ns, nonsignificant.