A kinome-wide siRNA screen identifies MARK4 as positive regulator of ciliogenesis. (A) Screen flowchart. (B) Kinases positively regulating ciliogenesis. Functional notes are obtained from the Entrez Gene database. Asterisks indicate kinases presented in the ciliome database. (C) RPE1 cells, treated with nontargeting (control) or MARK4 siRNA, were serum starved for 48 h and stained for IFT88, polyglutamylated tubulin, and DNA (DAPI). The left images show merged images. Regions within the white boxes are shown at higher magnification on the right. (D) Percentages of ciliated cells. polyglu. tub., polyglutamylated tubulin; acetyl., acetylated; detyr., detyrosinated. (E) Total cell extracts of control and MARK4-depleted RPE1 cells were analyzed by immunoblotting. Actin served as a loading control. (F) NIH 3T3 cells treated with control or MARK4 siRNA were serum starved for 24 h and stained for polyglutamylated and γ-tubulin and DNA. Insets show higher magnification of the centrosome region. (G) Percentages of ciliated cells determined using polyglutamylated tubulin. (H) Same as in E, except using extracts of NIH 3T3 cells. The asterisk indicates an unspecific band. Data are means ± SD of three independent experiments.