Disruption of kinesin II function using a dominant negative-acting transgene in Xenopus laevis rods results in photoreceptor degeneration.

PURPOSE: Kinesin II is a motor protein that moves on microtubules and whose importance in ciliary and flagellar transport has been well documented. In the current study, the role of kinesin II in rod photoreceptors was examined by expressing a dominant negative-acting transgene that disrupts kinesin II function in Xenopus laevis rods of transgenic tadpoles.
METHODS: A previously characterized dominant negative-acting kinesin II transgene tagged with enhanced green fluorescent protein (EGFP) driven by the Xenopus rod opsin promoter was used to make Xenopus transgenic tadpoles to disrupt kinesin II function specifically in rod photoreceptors. Transgenic tadpole retinas were examined to ascertain transgene expression pattern and morphologic phenotype. Rod-to-cone ratios were determined in experimental and control retinas.
RESULTS: Visualized by its EGFP tag, the kinesin II transgene was expressed in rods in a mosaic pattern in the retina. Subcellular localization of transgenic kinesin II was similar to that of endogenous kinesin II subunit photoreceptor expression-that is, it was localized to the connecting cilium, inner segment, and synapse. However, in kinesin II transgene-expressing animals, fluorescence was transient. Ocular fluorescence was lost 6 days after its first detection. The disappearance of fluorescence was due to degeneration of rods expressing the transgene. Retinas of 7- to 9-day old kinesin II transgenic tadpoles had significantly fewer rods than did control retinas.
CONCLUSIONS: The observation that rod degeneration is produced by expression of a dominant negative-acting kinesin II transgene in Xenopus rods is consistent with previous studies in mice, suggesting that kinesin II function is required for photoreceptor survival.