CEP290 regulates entry of Rab8a into the primary cilium and interacts with Rab8a in vivo. (A) RPE-1 cells transfected with control or CEP290 siRNAs, induced to quiescence, and stained with antibodies to glutamylated tubulin (GT335, green), Rab8a or polaris (red), and with DAPI (blue). A ciliated cell is shown in each case. Bar: 10 μM; insets: 2 μM. (B) A histogram quantifying the percentage of ciliated cells that were positive for Rab8a at the cilium. About 100 cells from the ciliated population of cells treated with control or CEP290 siRNA were scored, and the averages of four independent experiments were shown. Error bars represent +/- S.D. (C) Western blotting of CEP290 and Rab8a in RPE-1 cells treated with control or CEP290 siRNAs. α-tubulin was used as a loading control. (D) Western blotting of endogenous CEP290, CP110 and Rab8a after immunoprecipitation with anti-Flag (control), anti-CEP290, anti-CP110, or anti-Rab8a antibodies from growing or quiescent 3T3 cell extracts. IN, input.