Open Sesame: How Transition Fibers and the Transition Zone Control Ciliary Composition

Garcia-Gonzalo, Francesc R.; Reiter, Jeremy F.

doi:10.1101/cshperspect.a028134

Cited by 232 publications

(240 citation statements)

References 188 publications

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“…At least four complementary mechanisms have evolved to achieve this specialization: a soluble protein gate reminiscent of a molecular sieve, a membrane diffusion barrier at the TZ, a molecular motordriven intraflagellar transport (IFT) system, and a lipidated protein intraflagellar targeting (LIFT) system (reviewed in [5,44,63]). …”

Section: Box 1 Outstanding Questionsmentioning

confidence: 99%

“…There are different ways to establish a membrane diffusion barrier [5]. What about the soluble protein gate?…”

Section: Box 1 Outstanding Questionsmentioning

confidence: 99%

“…The distal appendages (transition fibers) connect to the membrane at the ciliary base. Immediately distal to the basal body is the transition zone (TZ), characterized by 'Ylinks' which make axoneme-to-membrane connections [5]. Together, the transition fibers and TZ are thought to make up a ciliary gate which maintains the protein and membrane composition-hence, specialization-of the ciliary compartment ( Figure 2).…”

Section: Introductionmentioning

confidence: 99%

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Gates for soluble and membrane proteins, and two trafficking systems (IFT and LIFT), establish a dynamic ciliary signaling compartment

Jensen

Leroux

2017

Current Opinion in Cell Biology

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Section: Box 1 Outstanding Questionsmentioning

confidence: 99%

“…There are different ways to establish a membrane diffusion barrier [5]. What about the soluble protein gate?…”

Section: Box 1 Outstanding Questionsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Gates for soluble and membrane proteins, and two trafficking systems (IFT and LIFT), establish a dynamic ciliary signaling compartment

Jensen

Leroux

2017

Current Opinion in Cell Biology

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“…The transition zone is believed to serve as a gatekeeper to selectively allow only ciliary proteins to enter the cilia, thus controlling the protein composition in cilia (Garcia-Gonzalo and Reiter, 2017). How ciliary proteins are selectively transported into cilia remains poorly understood.…”

Section: Introductionmentioning

confidence: 99%

Three Tctn proteins are functionally conserved in the regulation of neural tube patterning and Gli3 processing but not ciliogenesis and Hedgehog signaling in the mouse

Wang

Meng

et al. 2017

Developmental Biology

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Tctn1, Tctn2, and Tctn3 are membrane proteins that localize at the transition zone of primary cilia. Tctn1 and Tctn2 mutations have been reported in both humans and mice, but Tctn3 mutations have been reported only in humans. It is also not clear whether the three Tctn proteins are functionally conserved with respect to ciliogenesis and Hedgehog (Hh) signaling. In the present study, we report that loss of Tctn3 gene function in mice results in a decrease in ciliogenesis and Hh signaling. Consistent with this, Tctn3 mutant mice exhibit holoprosencephaly and randomized heart looping and lack the floor plate in the neural tube, the phenotypes similar to those of Tctn1 and Tctn2 mutants. We also show that overexpression of Tctn3, but not Tctn1 or Tctn2, can rescue ciliogenesis in Tctn3 mutant cells. Similarly, replacement of Tctn3 with Tctn1 or Tctn2 in the Tctn3 gene locus results in reduced ciliogenesis and Hh signaling, holoprosencephaly, and randomized heart looping. Surprisingly, however, the neural tube patterning and the proteolytic processing of Gli3 (a transcription regulator for Hh signaling) into a repressor, both of which are usually impaired in ciliary gene mutants, are normal. These results suggest that Tctn1, Tctn2, and Tctn3 are functionally divergent with respect to their role in ciliogenesis and Hh signaling but conserved in neural tube patterning and Gli3 processing.

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“…Immediately distal to the distal appendages is a subcompartment of the cilium called the transition zone [47]. The transition zone is named for the most proximal region in which the triplet microtubules that comprise the basal body have transitioned into the doublet microtubules of the ciliary axoneme.…”

Section: Different Subdomains Of the Cilium Have Distinct Membranesmentioning

confidence: 99%

How the Ciliary Membrane Is Organized Inside-Out to Communicate Outside-In

2018

Self Cite

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Cilia, organelles that move to execute functions like fertilization and signal to execute functions like photoreception and embryonic patterning, are composed of a core of nine-fold doublet microtubules overlain by a membrane. Distinct types of cilia display distinct membrane morphologies, ranging from simple domed cylinders to the highly ornate invaginations and membrane disks of photoreceptor outer segments. Critical for the ability of cilia to signal, both the protein and the lipid compositions of ciliary membranes are different from those of other cellular membranes. This specialization presents a unique challenge for the cell as, unlike membrane-bounded organelles, the ciliary membrane is contiguous with the surrounding plasma membrane. This distinct ciliary membrane is generated in concert with multiple membrane remodeling events that comprise the process of ciliogenesis. Once the cilium is formed, control of ciliary membrane composition relies on discrete molecular machines, including a barrier to membrane proteins entering the cilium at a specialized region of the base of the cilium called the transition zone and a trafficking adaptor that controls G protein-coupled receptor (GPCR) localization to the cilium called the BBSome. The ciliary membrane can be further remodeled by the removal of membrane proteins by the release of ciliary extracellular vesicles that may function in intercellular communication, removal of unneeded proteins or ciliary disassembly. Here, we review the structures and transport mechanisms that control ciliary membrane composition, and discuss how membrane specialization enables the cilium to function as the antenna of the cell.

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Open Sesame: How Transition Fibers and the Transition Zone Control Ciliary Composition

Cited by 232 publications

References 188 publications

Gates for soluble and membrane proteins, and two trafficking systems (IFT and LIFT), establish a dynamic ciliary signaling compartment

Gates for soluble and membrane proteins, and two trafficking systems (IFT and LIFT), establish a dynamic ciliary signaling compartment

Three Tctn proteins are functionally conserved in the regulation of neural tube patterning and Gli3 processing but not ciliogenesis and Hedgehog signaling in the mouse

How the Ciliary Membrane Is Organized Inside-Out to Communicate Outside-In

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