The reference OMIM entry for this protein is 615776

Ciliary rootlet coiled-coil protein; crocc
Rootletin
Kiaa0445

DESCRIPTION

The ciliary rootlet is a large cytoskeletal component of ciliated cells. In photoreceptors, the ciliary rootlet originates from the proximal ends of basal bodies and spans the length of the cell. CROCC, or rootletin, is the major structural component of the ciliary rootlet. CROCC also forms the linker between paired centrioles in nonciliated cells (summary by Yang et al., 2006).

CLONING

By sequencing clones from a size-fractionated human brain cDNA library, Ishikawa et al. (1997) obtained a partial CROCC clone, which they designated KIAA0445. The deduced protein shares significant similarity with Onchocerca volvulus major antigen. PCR analysis revealed variable CROCC expression in all human tissues examined. Yang et al. (2002) cloned full-length mouse Crocc, which they called rootletin. The deduced 2,009-amino acid protein has a calculated molecular mass of 227 kD. The protein was predicted to fold into an N-terminal globular domain followed by an extended coiled-coil rod domain. Rootletin shares significant structural similarity with the centrosomal protein Cnap1 (CEP2; 609689). Western blot analysis detected rootletin at an apparent molecular mass of 220 kD, with highest expression in mouse retina, followed by brain, trachea, and kidney. Immunohistochemical analysis detected rootletin in all major ciliated epithelia, with prominent expression in tissues with highly developed rootlets. In retina, rootletin staining mirrored the rootlet, which extended from the basal body to synaptic terminals and anchored the endoplasmic reticulum along its length. In cells that do not develop cilia, rootletin localized to tiny speckles that overlapped with centrioles, and centriole staining disappeared at anaphase. Immunoelectron microscopy of mouse retina detected rootletin as protofilaments of approximately 10 nm diameter, although the shapes and dimensions of the bundles were highly variable. Bahe et al. (2005) cloned full-length human rootletin. Western blot analysis detected rootletin at an apparent molecular mass of 228 kD in purified centrosomes isolated from human U2OS cells. Immunofluorescence microscopy revealed rootletin as thin fibers protruding away from the 2 centrioles.

GENE FUNCTION

By expression in COS cells, Yang et al. (2002) found that mouse rootletin was sufficient to induce rootlet formation. Rootletin formed parallel homodimers and elongated higher order polymers. Domain analysis revealed that the globular N-terminal domain localized to the microtubule organizing center, but was dispensable for formation of filaments. The isolated rod domain of rootletin remained competent in filament elongation. Yeast 2-hybrid analysis of a mouse retina cDNA library revealed that the N-terminal head domain of rootletin interacted with kinesin light chain-3 (KLC3; 601334). Bahe et al. (2005) found that overexpression of human rootletin in U2OS cells resulted in formation of filaments that emanated from centrosomes at low expression levels but filled the cytoplasm at higher levels. Coexpression of fluorescence-tagged centrosomal proteins NEK2 (604043) or CNAP1 resulted in their recruitment to rootletin filaments. In vitro kinase assays revealed that NEK2 phosphorylated rootletin, likely at several sites. Depletion of rootletin via small interfering RNA caused centrosome splitting, but it did not alter association of CNAP1 with centrioles. In contrast, depletion of CNAP1 loosened the association of root ... More on the omim web site

Subscribe to this protein entry history

June 30, 2020: Protein entry updated
Automatic update: OMIM entry 615776 was added.

Oct. 19, 2018: Additional information
Initial protein addition to the database. This entry was referenced in Bryk and co-workers. (2017).