November 7, 2011

Actin is that super achieving big man-or-woman on campus who seems to be involved in and excelling at everything. Even if you roll your eyes at actin’s achievements and wonder what actin ISN’T involved in, you’re secretly impressed and jealous. Today’s image is from a paper on axon guidance and the role of the actin regulators WAVE and WASP.

Like many developmental processes, the guidance and mobility of developing axons depends on a dynamic actin cytoskeleton. Because most neuronal networks are quite complex, the use of the fruit fly’s eye provides biologists with a genetically-tractable model for understanding axon growth and guidance. The fly’s eye is a compound eye—there are 750 individual eyes called ommatidia, each comprised of 8 light-sensitive photoreceptor neurons (R-cells). A recent study tests the roles of two actin nucleating regulators called WASP and WAVE in R-cell axon targeting. In this study, Stephan and colleagues found that a protein called Abi regulates WAVE by ensuring its membrane localization, where WAVE activates the Arp2/3 actin nucleating complex. While WAVE is required for R-cell axon guidance, WASP is not. The images above show R-cell axons (green) in flies with different genetic backgrounds. Wild-type flies (left) and
wasp mutants (right) have regular patterns and spacing of axons, while wave mutants (middle) have bundled or clumped axons with irregular spacing.

ResearchBlogging.orgStephan, R., Gohl, C., Fleige, A., Klambt, C., & Bogdan, S. (2011). Membrane-targeted WAVE mediates photoreceptor axon targeting in the absence of the WAVE complex in Drosophila Molecular Biology of the Cell, 22 (21), 4079-4092 DOI: 10.1091/mbc.E11-02-0121

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