Focus on Molecules: Rootletin
Section snippets
Structure
Rootletin (accession number NP_742120) is a large coiled coil protein initially identified as a structural component of the ciliary rootlet (Yang et al., 2002). Its formal designation (ciliary rootlet coiled-coil, rootletin), as listed in most databases, reflects these two known aspects of the protein. The murine rootletin comprises 2009 amino acid residues and has a calculated molecular weight of about 220 kDa. The C-terminal three quarters of rootletin sequence are predicted to form an
Function
As its name implies, the primary function of rootletin is to serve as a constituent of the rootlet. Over-expression of recombinant rootletin in cell culture leads to the formation of rootlets that are morphologically similar to those of native tissues. No co-polymers of rootletin have been found by immunoprecipitation studies. Targeted disruption of rootletin gene in mice abolished the formation of ciliary rootlets (Yang et al., 2005). These data indicate that rootletin is the major, and likely
Disease involvement
No human disease has been formally linked to rootletin at this time. Given the fact that rootletin is essential for photoreceptor maintenance in the mouse, it is a possibility that genetic defects in rootletin may be a cause of human retinal degeneration, in either simplex or syndromic forms. Based on all available data, the corresponding human retinal degeneration may be one of late onset, may present with systemic manifestations of a ciliary defect, and may be sensitive to environmental
Future studies
While our understanding of rootletin function has come a long way since its discovery three years ago, many questions remain. We do not yet know, first and foremost, whether rootletin is a causative gene for human retinal degeneration and/or other disease conditions. Second, it remains to be demonstrated if and to what extent rootletin is involved in intracellular trafficking. Third, whether rootletin has a role in centriolar function such as cohesion and replication needs to be explored.
References (3)
- Yang, J., Li, T., 2005. The ciliary rootlet interacts with kinesin light chains and may provide a scaffold for...
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Insights into photoreceptor ciliogenesis revealed by animal models
2019, Progress in Retinal and Eye ResearchCitation Excerpt :The photoreceptor ciliary rootlet originates at the basal body and extends to the synaptic terminal. It is composed of rootletin (2009 amino acids, isoform 1), a 220-kD protein with multiple coiled-coil domains identified first in retina (Fig. 8B) (Yang and Li, 2006; Yang et al., 2002). Rootlets are homopolymeric rootletin protofilaments bundled into variably-shaped thick filaments that connect the basal body and daughter centriole and support the slender photoreceptor cell body (Yang et al., 2002).
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