Fig. 1
5-HT6 regulated the length of primary cilia in APP/PS1 mice. (a) Overexpression of 5-HT6 induced elongation and branched primary cilia in hippocampal neurons. 5-HT6 (green) and ARL13B (purple) indicated primary cilia. DAPI indicated nuclei. (b) Overexpression of 5-HT6 increased the length and branching numbers of primary cilia. Cilia length, **p < 0.01 (t test); number of branches, **p < 0.01 (Mann–Whitney U test). (c) Knocking down 5-HT6 decreased the length of primary cilia in hippocampal neurons. (d) Length of primary cilia was reduced by siRNA against 5-HT6. Cilia length, **p < 0.01 (Mann–Whitney U test). The branching number of primary cilia was unchanged (remaining at 1) after exposure to siRNA against 5-HT6. Number of branches, p = 0.62 (t test). (e) Primary cilia elongated gradually with increasing 5-HT6 transfection. 5-HT6 (green) indicated primary cilia. (f) Cilia length increased with upregulated 5-HT6. All groups were compared with the control group, which was transfected with no vectors. 0.5 μg, ***p < 0.001; 1 μg, ***p < 0.001; 2 μg, ***p < 0.001 (Kruskal–Wallis test, p < 0.001). (g) Primary cilia length increased as the 5-HT concentration increased. 5-HT6 (green) and ARL13B (red) were markers of primary cilia. MAP2 (purple) served as a neuronal marker. (h) Ciliary length was elongated by 5-HT in a gradual and concentration-dependent manner. All groups were compared with the control group to which was applied 0 nM 5-HT. 2 nM, **p < 0.01; 200 nM, ***p < 0.001 (one-way ANOVA, F 2,121 = 220.6, p < 0.001). (i) siRNA against 5-HT6 decreased the primary ciliary length of hippocampal neurons in APP/PS1 mice. AC3 (red) indicated primary cilia. (j) Knocking down 5-HT6 reduced the ciliary length of hippocampal neuron in APP/PS1 and WT mice. All groups were compared with the group exposed to scrambled siRNA. siRNA versus Scramble in WT, *p < 0.05; siRNA versus Scramble in APP/PS1, **p < 0.01 (two-way ANOVA: interaction, F 1,195 = 224.8, p < 0.001; treatment, F 1,195 = 417.6, p < 0.001; gene, F 1,195 = 389.6, p < 0.001). Scale bars, 10 μm. All data presented as mean ± SEM (≥3 independent experiments). 5-HT6, serotonin 6 receptor, DAPI 4',6-diamidino-2-phenylindole, EGFP enhanced green fluorescent protein