Cby1 promotes Ahi1 recruitment to a ring-shaped domain at the centriole-cilium interface and facilitates proper cilium formation and function.
Bottom Line: Defects in centrosome and cilium function are associated with phenotypically related syndromes called ciliopathies.Superresolution microscopy using both three-dimensional SIM and STED reveals that Cby1 localizes to an ∼250-nm ring at the distal end of the mature centriole, in close proximity to Ofd1 and Ahi1, a component of the transition zone between centriole and cilium.This suggests that Cby1 is required for efficient recruitment of Ahi1, providing a possible molecular mechanism for the ciliogenesis defect in Cby1(-/-) cells.
Affiliation: Department of Biology, Stanford School of Medicine, Stanford University, Stanford, CA 94305.Show MeSH
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Mentions: To test directly whether loss of Cby1 compromises cilium formation, we examined primary cilium formation in mouse embryonic fibroblasts (MEFs) from Cby1+/+ and Cby1−/− embryos. Cells were induced to form a cilium by serum starvation and assayed over a 72-h time course. Cby1−/− MEFs exhibited a delay in primary cilia formation relative to wild type (Figure 2, A and B). After 24 h of serum starvation, >40% of Cby1+/+ MEFs had a cilium, whereas <5% of Cby1−/− MEFs had a cilium (Figure 2B). The fraction of Cby1−/− MEFs with a cilium increased over time of serum starvation, although it remained lower than that for Cby1+/+ MEFs (Figure 2B). Complementation of the Cby1−/− deletion with a human GFP-Cby1 construct (Figure 2, C and D) rescued the defect in primary cilium formation, assessed at 24 h of serum starvation. Unlike in previous RNAi experiments (Steere et al., 2012), these data demonstrate that Cby1 is not essential for forming a primary cilium but is important for facilitating the process.
Affiliation: Department of Biology, Stanford School of Medicine, Stanford University, Stanford, CA 94305.