(A) Representative images of tip cells from Myh9 WT and Myh9 EC-KO mouse retinas labeled for pPax Y118 (blue), activated ITGB1 (aITGB1, green), and CD31 (red). (Scale bar, 10 µm.) Red arrowheads point to sites enriched in aITGB1 and pPAX at the base of filopodia in Myh9 WT tip cells, which is absent or more homogenously distributed along dactylopodia of Myh9 EC-KO tip cells. (Scale bar, 20 µm.) (B) Box plot of pPax fluorescence in tip cells from Myh9 WT (n = 9 retinas) and Myh9 EC-KO (n = 8 retinas) mouse retinas. P value from unpaired Student’s t test. (C) Representative images of HUVECs expressing CAAX-Venus at the cell membrane in DMSO, BBS, CK666, and BBS + CK666 conditions. HUVECs are labeled for aITGB1 (red), cell membrane (CAAX-Venus, green), and nuclei (DAPI, gray). (Scale bar, 10 µm.) (D) Box plots of pPax fluorescence intensity and aITGB1 fluorescence intensity in HUVECs expressing CAAX-Venus at the cell membrane in DMSO (n = 20 cells), BBS (n = 15 cells), CK666 (n = 24 cells), and BBS + CK666 (n = 13 cells) conditions. P values from one-way ANOVA. (E) Western blot analysis of levels of active GTP-bound Rac1 and total Rac1 in DMSO- or BBS-treated HUVECs. (F) Representative images of HUVECs expressing CAAX-Venus at the cell membrane in NSC23766 and NSC23766 + BBS conditions. HUVECs are labeled for aITGB1 (red), cell membrane (CAAX-Venus, green), and nuclei (DAPI, gray). (Scale bar, 10 µm.) (G) Box plot of filopodia number in DMSO (n = 21 cells), BBS (n = 20 cells), NSC23766 (n = 18 cells), and NSC23766 + BBS (n = 20 cells). P values from one-way ANOVA. (H) Representative images of HUVECs expressing CAAX-Venus at the cell membrane in siArhgef7 HUVECs treated with DMSO or BBS. HUVECs are labeled for aITGB1 (red), cell membrane (CAAX-Venus, green), and nuclei (DAPI, gray). (Scale bar, 10 µm.) (I) Box plot of filopodia number in siControl and siArhgef7 HUVECs treated with DMSO (n = 6 cells in siControl and 10 in siArhgef7) or BBS (n = 10 cells in siControl and 11 in siArhgef7). P values from one-way ANOVA.