The ciliary transition zone functions in cell adhesion but is dispensable for axoneme assembly in C. elegans.

Cilia are cellular projections that perform sensory and motile functions. A key ciliary subdomain is the transition zone, which lies between basal body and axoneme. Previous work in Caenorhabditis elegans identified two ciliopathy-associated protein complexes or modules that direct assembly of transition zone Y-links. Here, we identify C. elegans CEP290 as a component of a third module required to form an inner scaffolding structure called the central cylinder. Co-inhibition of all three modules completely disrupted transition zone structure. Surprisingly, axoneme assembly was only mildly perturbed. However, dendrite extension by retrograde migration was strongly impaired, revealing an unexpected role for the transition zone in cell adhesion.