C2cd3 is critical for centriolar distal appendage assembly and ciliary vesicle docking in mammals

Abstract

The primary cilium plays critical roles in vertebrate development and physiology, but the mechanisms underlying its biogenesis remain poorly understood. We investigated the molecular function of C2 calcium-dependent domain containing 3 (C2cd3), an essential regulator of primary cilium biogenesis. We show that C2cd3 is localized to the centriolar satellites in a microtubule-and Pcm1-dependent manner; however, C2cd3 is dispensable for centriolar satellite integrity. C2cd3 is also localized to the distal ends of both mother and daughter centrioles and is required for the recruitment of five centriolar distal appendage proteins: Sclt1, Ccdc41, Cep89, Fbf1, and Cep164. Furthermore, loss of C2cd3 results in failure in the recruitment of Ttbk2 to the ciliary basal body as well as the removal of Cp110 from the ciliary basal body, two critical steps in initiating ciliogenesis. C2cd3 is also required for recruiting the intraflagellar transport proteins Ift88 and Ift52 to the mother centriole. Consistent with a role in distal appendage assembly, C2cd3 is essential for ciliary vesicle docking to the mother centriole. Our results suggest that C2cd3 regulates cilium biogenesis by promoting the assembly of centriolar distal appendages critical for docking ciliary vesicles and recruiting other essential ciliogenic proteins.

WDR8 is a centriolar satellite and centriole-associated protein that promotes ciliary vesicle docking during ciliogenesis

“…Failure in vesicle docking to distal ends of centrioles has been previously reported for components of distal appendages, such as Cep164 and Cep123, that serve as adaptors for the binding of vesicles to the distal ends (Schmidt et al, 2012;Sillibourne et al, 2013;Tanos et al, 2013;Burke et al, 2014;Joo et al, 2013;Ye et al, 2014). Our data show that WDR8 or Cep135 knockdown does not decrease the centriolar levels of Cep164 or Cep123.…”

“…Distal appendage proteins, including Cep164 and Cep123 (also known as Cep89), have been reported to be indispensable for this initial step of ciliary membrane biogenesis (Schmidt et al, 2012;Tanos et al, 2013;Joo et al, 2013;Sillibourne et al, 2013;Burke et al, 2014;Ye et al, 2014). Moreover, a cascade of small GTPases regulates vesicle docking and fusion at the mother centriole.…”

Intraflagellar transport protein IFT52 recruits IFT46 to the basal body and flagella

“…Some factors such as BBS7, BBS8, C2cd3, CCDC41, OFD1, Rsg1 and TTBK2 affect the recruitment of certain IFT subunits to the basal body (Blacque et al, 2004;Brooks and Wallingford, 2013;Goetz et al, 2012;Joo et al, 2013;Ye et al, 2014), but their functions are unspecific (Toriyama et al, 2016). Recently, ciliogenesis and planar polarity effectors (CPLANEs), including Jbts17, Intu, Fuz, Wdpcp and Rsg1, have been shown to recruit peripheral IFT-A proteins to basal bodies (Brooks and Wallingford, 2012;Toriyama et al, 2016).…”

Centrin 2 Is Required for Mouse Olfactory Ciliary Trafficking and Development of Ependymal Cilia Planar Polarity

“…The basal body at the ciliary base appears to be critical for both entry of the signaling protein and establishment of planar polarity (Marshall, 2008b). The basal body distal appendage, or "transitional fiber", together with the ciliary transition zone, may compromise a "gate" for ciliary entry (Williams et al, 2011;Wei et al, 2013;Ye et al, 2014), whereas the subdistal appendage, or "basal foot", determines polarity, with its absence in mice causing uncoordinated ciliary beating (Kunimoto et al, 2012).…”