Abstract
Purpose: :
Intraflagellar transport (IFT) is thought to be essential for photoreceptor OS development. In multiple types of cilia and flagella the heterotrimeric Kif3 complex, a kinesin 2 family member, plays an essential role in anterograde IFT. Recently, we showed in zebrafish that an alternative anterograde kinesin, Kif17, associates with IFT proteins along the photoreceptor axoneme. A splice-blocking morpholino oligonucleotide targeted against Kif17 blocks OS development with little or no effect on other embryonic systems. In order to evaluate the relative importance of the two kinesins in photoreceptor OS development we have directly compared the phenotypes induced by morpholino knockdown of Kif17 and Kif3b.
Methods: :
We identified the Kif3b subunit of the Kif3 complex in the zebrafish genomic sequence by protein blast analysis, and injected a morpholino designed to inhibit the translation of Kif3b into one cell stage zebrafish embryos. The effects of the Kif3b morpholino were compared to those seen using the Kif17 morpholino. Western blots were performed to confirm that the morpholino depleted the targeted kinesin without effecting the other. Phenotypes were analyzed at the gross morphological and microscopic levels as well as with immunocytochemical staining on frozen sections.
Results: :
Kif17 morphants developed normally, exhibited ocular, kidney and heart structures, but at 3 dpf showed defective ROS formation with mis-targeted cone photopigment. In contrast, Kif3b morphants presented multiple phenotypes including polycystic kidneys, heart edemas, small body, and downward curvature of the tail. Nonetheless, they developed short cone OS with normal localization of their photopigment.
Keywords: photoreceptors • cytoskeleton • retinal degenerations: cell biology