PUBLICATION

Loss-of-function of the ciliopathy protein Cc2d2a disorganizes the vesicle fusion machinery at the periciliary membrane and indirectly affects Rab8-trafficking in zebrafish photoreceptors

Authors
Ojeda Naharros, I., Gesemann, M., Mateos, J.M., Barmettler, G., Forbes, A., Ziegler, U., Neuhauss, S.C.F., Bachmann-Gagescu, R.
ID
ZDB-PUB-171228-3
Date
2017
Source
PLoS Genetics   13: e1007150 (Journal)
Registered Authors
Bachmann-Gagescu, Ruxandra, Forbes, Austin, Gesemann, Matthias, Neuhauss, Stephan
Keywords
none
MeSH Terms
  • Protein Transport
  • Membranes/metabolism
  • Animals
  • Zebrafish Proteins/genetics*
  • Zebrafish Proteins/metabolism*
  • Animals, Genetically Modified
  • rab GTP-Binding Proteins/genetics
  • rab GTP-Binding Proteins/metabolism*
  • Photoreceptor Cells, Vertebrate/metabolism
  • Zebrafish
  • Opsins/genetics
  • Opsins/metabolism
  • Humans
  • Cell Movement
  • Biological Transport
  • Vesicular Transport Proteins/genetics*
  • Vesicular Transport Proteins/metabolism*
  • Cilia/genetics
  • Cilia/metabolism
(all 19)
PubMed
29281629 Full text @ PLoS Genet.
Abstract
Ciliopathies are human disorders caused by dysfunction of primary cilia, ubiquitous organelles involved in transduction of environmental signals such as light sensation in photoreceptors. Concentration of signal detection proteins such as opsins in the ciliary membrane is achieved by RabGTPase-regulated polarized vesicle trafficking and by a selective barrier at the ciliary base, the transition zone (TZ). Dysfunction of the TZ protein CC2D2A causes Joubert/Meckel syndromes in humans and loss of ciliary protein localization in animal models, including opsins in retinal photoreceptors. The link between the TZ and upstream vesicle trafficking has been little explored to date. Moreover, the role of the small GTPase Rab8 in opsin-carrier vesicle (OCV) trafficking has been recently questioned in a mouse model. Using correlative light and electron microscopy and live imaging in zebrafish photoreceptors, we provide the first live characterization of Rab8-mediated trafficking in photoreceptors in vivo. Our results support a possibly redundant role for both Rab8a/b paralogs in OCV trafficking, based on co-localization of Rab8 and opsins in vesicular structures, and joint movement of Rab8-tagged particles with opsin. We further investigate the role of the TZ protein Cc2d2a in Rab8-mediated trafficking using cc2d2a zebrafish mutants and identify a requirement for Cc2d2a in the latest step of OCV trafficking, namely vesicle fusion. Progressive accumulation of opsin-containing vesicles in the apical portion of photoreceptors lacking Cc2d2a is caused by disorganization of the vesicle fusion machinery at the periciliary membrane with mislocalization and loss of the t-SNAREs SNAP25 and Syntaxin3 and of the exocyst component Exoc4. We further observe secondary defects on upstream Rab8-trafficking with cytoplasmic accumulation of Rab8. Taken together, our results support participation of Rab8 in OCV trafficking and identify a novel role for the TZ protein Cc2d2a in fusion of incoming ciliary-directed vesicles, through organization of the vesicle fusion machinery at the periciliary membrane.
Genes / Markers
Figures
Figure Gallery (17 images) / 2
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Expression
Phenotype
Fish Conditions Stage Phenotype Figure
cc2d2aw38/w38controlProtruding-mouth
cc2d2aw38/w38controlProtruding-mouth
cc2d2aw38/w38controlDay 4
cc2d2aw38/w38controlDay 4
cc2d2aw38/w38controlDay 4
cc2d2aw38/w38controlDay 4
cc2d2aw38/w38controlDay 4
cc2d2aw38/w38controlDay 5
cc2d2aw38/w38controlDay 5
cc2d2aw38/w38controlDay 5
1 - 10 of 19
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Mutations / Transgenics
Allele Construct Type Affected Genomic Region
a9
    		Complex
    tz288
      		Point Mutation
      w2
        		Point Mutation
        w38
          		Point Mutation
          zh401TgTransgenic Insertion
            zh402TgTransgenic Insertion
              zh403TgTransgenic Insertion
                zh404TgTransgenic Insertion
                  zh405TgTransgenic Insertion
                    1 - 9 of 9
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                    Human Disease / Model
                    No data available
                    Sequence Targeting Reagents
                    No data available
                    Fish
                    Fish
                    cc2d2aw38/w38
                    cc2d2aw38/w38; mitfaw2/w2; mpv17a9/a9; zh403Tg
                    ift88tz288/tz288
                    mitfaw2/w2; mpv17a9/a9; zh401Tg
                    mitfaw2/w2; mpv17a9/a9; zh401Tg; zh404Tg
                    mitfaw2/w2; mpv17a9/a9; zh402Tg
                    mitfaw2/w2; mpv17a9/a9; zh403Tg
                    mitfaw2/w2; mpv17a9/a9; zh404Tg
                    WT
                    1 - 9 of 9
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                    Antibodies
                    Orthology
                    Engineered Foreign Genes
                    Marker Marker Type Name
                    EGFPEFGEGFP
                    mCherryEFGmCherry
                    1 - 2 of 2
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                    Mapping
                    No data available
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                    Citation
                    Ojeda Naharros, I., Gesemann, M., Mateos, J.M., Barmettler, G., Forbes, A., Ziegler, U., Neuhauss, S.C.F., Bachmann-Gagescu, R. (2017) Loss-of-function of the ciliopathy protein Cc2d2a disorganizes the vesicle fusion machinery at the periciliary membrane and indirectly affects Rab8-trafficking in zebrafish photoreceptors. PLoS Genetics. 13:e1007150.