May 2004
Volume 45, Issue 13
Free
ARVO Annual Meeting Abstract  |   May 2004
Gamma–Tubulin Immunolocalization at Microtubules in Diverse Cytoskeletal Systems in the Outer Segments of Rods and Cones
Author Affiliations & Notes
  • M.S. Eckmiller
    Vogt Brain Research Institute, Heinrich Heine University of Düsseldorf, Düsseldorf, Germany
  • Footnotes
    Commercial Relationships  M.S. Eckmiller, None.
  • Footnotes
    Support  FAUN–Stiftung/Nürnberg
Investigative Ophthalmology & Visual Science May 2004, Vol.45, 3640. doi:
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      M.S. Eckmiller; Gamma–Tubulin Immunolocalization at Microtubules in Diverse Cytoskeletal Systems in the Outer Segments of Rods and Cones . Invest. Ophthalmol. Vis. Sci. 2004;45(13):3640.

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Abstract

Abstract: : Purpose: To identify additional molecular components of the microtubule–based cytoskeletal systems within photoreceptor outer segments (OS) in a vertebrate retina with rods having multiple incisures, because accumulating evidence suggests that disturbances of the photoreceptor cytoskeleton can mediate hereditary degenerations of the human retina. Methods: Photoreceptor cells and OS dissociated from retinas of Xenopus toads were treated to indirect immunofluorescence with antibodies to gamma–tubulin or appropriate controls, and examined by fluorescence microscopy. Results: In rod and cone OS, immunoreactivity to gamma–tubulin occurred as a continuous streak of fluorescence along the ciliary axoneme. In rod OS, gamma–tubulin immunoreactivity also occurred as regularly–spaced punctae of fluorescence along longitudinal lines coinciding with the multiple incisures. There was no significant fluorescence in OS on control preparations. Thus, specific immunoreactivity to gamma–tubulin occurred in the OS of amphibian rods and cones at locations containing microtubules. The pattern of immunoreactivity to gamma–tubulin along microtubules at the axoneme and at the multiple incisures was diverse, consistent with the diverse features of these OS cytoskeletal systems in the rods and cones of both amphibian and human retinas. Conclusions: These findings identify gamma–tubulin as a novel component of all the microtubule–based cytoskeletal systems in the OS of photoreceptors. In other vertebrate cells, gamma–tubulin is a component of microtubule organizing centers and is required for the assembly of alpha/beta–tubulin heterodimers into microtubules. In previous studies gamma–tubulin was found in the inner segment of photoreceptors, at the centrioles/basal body of the connecting cilium. The present study demonstrates that gamma–tubulin also occurs in the OS of photoreceptors, in association with microtubules. This association suggests that at these locations in OS the microtubules are capable of assembling new components and growing, or else the gamma–tubulin performs a previously undescribed function, such as in the assembly or organization of multimolecular phototransductive signalling complexes. These findings may be clinically relevant, for example the association of gamma–tubulin with cytoskeletal systems that are diverse in the OS of rods and cones may help to clarify the different phenotypes of human pathologies (such as retinitis pigmentosa and macular degeneration) that can be mediated by disturbances in photoreceptor OS cytoskeletons.

Keywords: retinal degenerations: cell biology • photoreceptors • cytoskeleton 
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