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B. D. Perkins, B. Krock; Retrograde Intraflagellar Transport by Dynein Motors Is Not Essential for Photoreceptor Development or Arresting Translocation. Invest. Ophthalmol. Vis. Sci. 2009;50(13):2720.
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The formation and maintenance of cilia requires Intraflagellar Transport (IFT). Kinesin motors direct anterograde IFT and are essential for opsin trafficking to the photoreceptor outer segment. Whether photoreceptors require retrograde IFT movment by cytoplasmic dynein 1b has remained unexplored. The purpose of this study is to understand the role of retrograde IFT in photoreceptor cell biology, specifically that of arrestin translocation, through compromising cytoplasmic dynein-2 function
Antisense morpholino oligonucleotides designed against the dynein heavy chain (HC), light intermediate chain (LIC) and intermediate chain (IC) were used to knockdown target gene expression in zebrafish. These ‘morphants’ were then subjected to ultrastructural and immunohistochemical analyses of photoreceptors and other ciliated tissues. Additionally, we assayed the light-induced retrograde translocation of arrestin using a monoclonal arrestin antibody
Ultrastructural analysis of the dynein morphants revealed that HC morphants had shortened outer segments, while LIC and IC morphants appeared ultrastructurally normal. Opsins were not mislocalized in the dynein morphants. We observed robust light dependent translocation of visual arrestin in larval zebrafish photoreceptors consistent with previous studies in other systems. Additionally, this process was not compromised in dynein morphants. In contrast, the ciliated cells of the pronephros and nasal epithelium were severely affected in animals with compromised dynein function.
Retrograde IFT by dynein motors is not essential for early photoreceptor development or survival, and that it does not mediate the light-dependent retrograde translocation of visual arrestin. We cannot exclude the possibility that long-term photoreceptor survival requires retrograde IFT. This is the first description of light dependent translocation of arrestin in zebrafish. These results present the intriguing prospect of employing forward genetics in zebrafish to understanding the mechanisms underlying arrestin translocation. Additionally, our analysis of other ciliated cells show that retrograde IFT does play an important role in cilia maintenance in non-photoreceptor cells in the zebrafish.
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