Fig. 1. GFP-tagged Inv is detected at the base of primary cilium. (A) GFP-tagged Inv localization in vivo. GFP-tagged Inv (Inv-GFP) signal is detected at the tubule lumen from isolated renal tubules of Inv-GFP mice. Primary cilia were visualized by anti-acetylated -tubulin antibody (ac-tubulin; red). Merged picture of the boxed area is also shown. Inv-GFP signal is not present along the entire length of the primary cilium (arrowheads). Scale bar: 5 µm. (B) Visualization of primary cilia and Inv-GFP fluorescence from the top view (right) and from the side view (left) in living cells. Primary cilia of mouse renal epithelial cells derived from Inv-GFP mice were observed by Nomarski differential interference contrast (DIC). Primary cilia in a living cell can be seen as a dot when viewed from the top (arrowheads). The Inv-GFP signal is predominantly detected at the base of the primary cilium. Corresponding successive z-axis confocal images of both primary cilia and Inv-GFP fluorescence are available in supplementary material Movie 1. From the side view the Inv-GFP signal is also observed at the base of the primary cilium (white arrowheads). Scale bars: 5 µm. (C) Immunocytochemistry further confirms Inv-GFP localization. The primary cilium was detected with anti-acetylated -tubulin antibody (ac-tubulin; red), and the basal body and/or centrosome was detected with the anti--tubulin antibody (red). The Inv-GFP signal is predominantly detected at the base of the primary cilium, excluding the basal-body area. Localization of polycystin-2 (red) only partially overlaps with the Inv-GFP signal. Scale bars: 10 µm. Line scans of the fluorescent signal from `<sup>*</sup>' to `^**' of the inserted images are shown on the right. A.U., arbitrary units.