Rootletin (ROLT)

Rootletin is a protein encoded by the CROCC gene.The ciliary rootlet, first recognized over a century ago, is a prominent structure originating from the basal body at the proximal end of a cilium. Despite being the largest cytoskeleton, its structural composition has remained unknown.

Rootletin forms parallel in register homodimers and elongated higher order polymers mediated by the tail domain alone. The head domain may be required for targeting to the basal body and binding to a kinesin light chain. In retinal photoreceptors where rootlets appear particularly robust, rootlets extend from the basal bodies to the synaptic terminals and anchor ER membranes along their length. Thus, rootletin is the long-sought structural component of the ciliary rootlet.