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J. Lin–Jones, B. Burnside; A GFP–retinal Fascin 2 Fusion Protein Colocalizes With Actin Filament Bundles of Rod Inner Segments and Calycal Processes in Transgenic Xenopus Tadpoles . Invest. Ophthalmol. Vis. Sci. 2005;46(13):3960.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Fascin 2 is an actin–filament crosslinker that is expressed exclusively in the retina. Human mutations in the fascin 2 gene result in autosomal dominant retinitis pigmentosa and macular degeneration, suggesting an important role for fascin 2 in the maintenance of functional photoreceptors. Previously, Saishin and coworkers immunolocalized bovine fascin 2 to photoreceptor inner and outer segments (IOVS 41:2087–2095, 2000). The purpose of our studies is to examine in more detail fascin 2 localization in photoreceptors. Methods: We have cloned fascin 2 from Xenopus and zebrafish retinal cDNA using PCR. Fascin 2 localization in photoreceptors was examined by using Xenopus fascin 2 tagged with green fluorescent protein in an expression vector containing a modified Xenopus rod opsin promoter to make transgenic tadpoles. Results: From zebrafish retinal cDNA, we cloned two fascin 2 genes that are 77% identical (86% similar) to each other and ∼62% identical (77% similar) to human fascin 2. Xenopus fascin 2 was also cloned from Xenopus retinal cDNA and is 65% identical (81% similar) to human fascin 2. Xenopus tadpoles expressing a GFP–tagged fascin 2 transgene displayed fluorescence in the rod inner segment, where it colocalized with inner segment actin filament bundles and calycal processes. Conclusions: Since fascins have been shown to crosslink actin filaments, the filament–bundle localization of fascin 2 suggests that fascin 2 plays an important role in maintaining the structural actin cytoskeleton of vertebrate photoreceptors. The finding that mutations in fascin–2 lead to retinitis pigmentosa further suggests that fascin 2 and the inner segment actin bundles play important roles in photoreceptor survival.
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