Molecular Regulation of Synaptogenesis in Drosophila
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Dynamic regulation of the actin cytoskeleton is required for synapses to form and maintain their shape. The actin cytoskeleton is regulated by Rho GTPases in response to genetic and extracellular signals. Rho GTPases are regulated by guanine nucleotide exchange factors and GTPase activating proteins (GAPs). Syd-1 is a protein that has been identified as necessary for synapse formation in worms, with similar proteins in flies, and mice. Little is known about the molecular mechanism by which Syd-1 is acting. While genetic techniques are great tools for examining synapse development, they are limited by their inability to consider the molecular nature of the protein product. By studying the biochemical nature of synaptic proteins, we can begin to understand their function with a new level of clarity. Syd-1 has a predicted Rho GAP domain; however it is thought to be inactive. The activity of the fly protein, Dsyd-1, has never been examined although it has been speculated that it is inactive in all invertebrates. Recently the mouse version was reported to have Rho GAP activity. By performing GTPase activity assays on purified proteins, I found the GAP domain of Dsyd-1 increased the GTPase activity of Rac-1 and Cdc42 but not RhoA. Members of our lab found the activity of Dsyd-1 is necessary for proper synapse formation both at the Drosophila neuromuscular junction as well as in R7 neurons. In Caenorhabditis elegans, Syd-1 was found to interact with presynaptic protein RSY-1. Since RSY-1 is evolutionarily conserved, I tested whether or not RSY-1 has a similar effect on R neurons in Drosophila. I also isolated mRNA from R neurons and evaluated the possibility of analyzing mutant neurons using comparative transcriptomics. This dissertation includes previously unpublished coauthored material.