Figure 1. Elements of the microtubule cytoskeleton within the cilium.

The axoneme consists of nine bundles of MTs that are anchored in the basal body. Free tubulin diffuses through the axoneme lumen [1] and accumulates at the ciliary base, transition zone, and cilium tip. Exchange of tubulin between cytoplasmic and ciliary pools regulates axoneme length [2]. IFT motors, kinesin and dynein, carry cargo along the axoneme in different directions. Microtubule-associated proteins localize along the cilium and at the basal body, including SAXO1 (green), MAP4 (orange), and septin family proteins (pink), which also associate with the membrane of the ciliary pocket.