Required for high-level Shh responses in the developing neural tube. Together with cdk20, controls the structure of the primary cilium by coordinating assembly of the ciliary membrane and axoneme, allowing gli2 to be properly activated in response to SHH signaling. Interacts with cdk20, which promotes cdk20 stability and function. Fish are viable during embryogenesis and early larval stages, but exhibit curvature of the body axis and hydrocephalus, and curled cilia in distal kidney tubules. The Rab-GAP TBC domain appears to be inactive, probably due to a lack of the essential Arg and Gln in the catalytic finger motifs.