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C. Insinna, J. C. Besharse; The Homodimeric Kinesin, KIF17, Is Required for Photoreceptor Outer Segment Development. Invest. Ophthalmol. Vis. Sci. 2007;48(13):4658.
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Along the CC, intraflagellar transport (IFT) is thought to facilitate the bidirectional trafficking of phototransduction components. In the current IFT model proposed for photoreceptors, kinesin 2 and dynein 2 are the IFT motors transporting IFT proteins along the axoneme. Recently, studies in C. elegans suggest that another IFT kinesin, Osm-3, is required specifically in the extension of distal singlet microtubules and may also move cargo along sensory cilia. Since the axoneme in photoreceptors is known to terminate in microtubule singlets we tested the hypothesis that Kif17, the mammalian homologue of the C. elegans Osm3-kinesin, plays an important role in outer segment formation.
We used immunocytochemistry and immunoprecipitation techniques to examine Kif17 expression in developing zebrafish and adult mouse photoreceptors. We also created zebrafish embryos deficient in Kif17 by injection of an antisense morpholino targeted against Kif17, and examined morphant phenotypes using immunofluorescence as well as light and transmission electron microscopy.
Our data show that Kif17 is localized along the cilia in the OS of mouse and zebrafish photoreceptor cells. Furthermore, Kif17 coimmunoprecipitates with rhodopsin in mouse retinal extracts. Finally, Kif17 morphants fail to develop OS after 3 days.
Our analysis demonstrates failed outer segment formation in retinas deficient in Kif17 protein. This coupled with immunopreciptiation data suggest that Kif17 is required for both overall assembly of outer segments, perhaps, through extension of distal microtubule singlets and for trafficking of specific IFT cargo such as rhodopsin.
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