The tilt series of transmission electron microscopy (TEM) samples were made from 24 hr serum-starved mouse embryonic fibroblasts (MEFs). Reconstructed tomograms are color-coded to highlight the ciliary membrane (brown), ciliary sheath (orange), ciliary pocket (yellow), basal body (purple), Golgi (green), electron-dense-coated vesicles (magenta), and vesicles lacking electron cloud (cyan). (A) Z-projections from 600 nm TEM serial tomograms of WT MEFs show a track of electron-dense vesicles between the Golgi and cilia (Figure 6—video 1). Arrows point at the path of vesicles between the Golgi and cilia. The image in the left panel is segmented in the right panel. (B) Z-projections from 300 nm tomograms from WT MEFs show electron-dense-coated vesicles close to the cilia base and along the length of the cilium (Figure 6—video 2). Arrows point at coated vesicles near the cilium. (C) Z-projections from 600 nm serial tomogram from Wdr35-/- MEFs have a massive accumulation of vesicles in a 2 µm radius of the cilia base (cyan), and these vesicles lack a visible coat, or electron-dense cloud on them (Figure 6—video 3). The length of cilia is drastically reduced, the ciliary membrane is wavy, and axoneme microtubules are broken in the mutant. (B, C) On left is the same Z-projection in the upper panel segmented in the lower panel, and on the right is another Z-projection from the same tomogram. Asterisk shows a coatless vesicle that fails to fuse with the ciliary sheath (see lower-left panel, C). Scale bars = 1 µm.