(A) Indirect immunofluorescence of Ccdc181 in sections of adult mouse testis (a-c), in dissected tracheal cartilages (d-f) and in NIH 3T3 cells induced for primary cilia formation (g-i) was performed using polyclonal anti-Ccdc181 (red) and monoclonal anti-acetylated α-Tubulin (green) antibodies. Additionally, nuclei were stained with DAPI (blue) (c, f, i). Ccdc181 predominantly localizes to sperm flagella, with a more intense staining at the midpiece (a-c). In tracheal epithelial cells, Ccdc181 was observed to localize to the basal part of motile cilia (d-f). In contrast, in NIH 3T3 cells Ccdc181 staining was absent in non-motile primary cilia, but was diffusely distributed in the cytosol (g-i). (B) The distribution of the relative fluorescence intensities of Ccdc181 and acetylated α-Tubulin along a single tracheal cilium (a-c, c arrow) is shown. In contrast to acetylated α-Tubulin, Ccdc181 predominantly localizes to the basal part of the tracheal cilium. Scale bar: 5 μm.