Down-regulation of caveolin (Cav)-1 promotes ciliogenesis. A, B) WI-38 (A) and IMR-90 (B) human diploid fibroblasts were infected with a lentivirus carrying caveolin-1 shRNA. Infection with a lentivirus carrying scrambled (Scr) shRNA was used as the control. Cells were cultured for 10 d, and cell lysates were collected for immunoblot analysis with antibody probes specific for caveolin-1 and p21. Immunoblot with anti-β-actin IgGs was performed to show equal loading. C, D) Caveolin-1 expression was down-regulated by shRNA in WI-38 and IMR-90 fibroblasts, as described in A and B. After 10 d, primary cilia formation was quantified by immunofluorescence staining with an antibody probe specific for acetylated α-tubulin. Quantification of ciliogenesis (C) and representative images (D) are shown. E, F) Caveolin-1 expression was down-regulated in WI-38 human diploid fibroblasts by caveolin-1 siRNA. Transfection of WI-38 cells with scrambled siRNA was performed as the control. After 10 d, caveolin-1, p21 and β-actin protein expression was determined by immunoblot analysis (E), whereas primary cilia formation was quantified by immunofluorescence staining with anti-acetylated α-tubulin IgGs (F). Values are means ± sem. *P < 0.001 (Student’s t test).