GENETIC DISSECTION--SYNAPTIC TRANSMISSION IN DROSOPHILA

神经系统功能的一个重要过程是突触

One process that is important for nervous system function is synaptic transmission, the process by which neurons communicate with each other and with target muscle cells. Neuronal ion channels play key roles in controlling this process. A more complete understanding of the mechanisms by which synaptic transmission can be regulated requires identification of the ion channel structural and regulatory components. However many of these components have as yet resisted molecular characterization. The long-term objective of this work is to use genetic methodology in Drosophila to identify and characterize these components. With genetic methodology, the genes that regulate synaptic transmission are identified by mutation. Because any gene can be mutated, any protein can be identified by mutation regardless of abundance, homology to previously characterized proteins or even prior knowledge of existence. Thus this approach provides a unique way identifying novel classes of functionally important molecules not accessible by other means. Once identified, the roles of these genes in controlling synaptic transmission are determined with electrophysiological assays, and finally the genes are cloned and sequenced which enables the encoded products to be studied at the molecular level. I previously identified mutations in three new genes that interact behaviorally with Shaker, the structural gene for the A type potassium channel. Electrophysiological analysis of these new mutants has shown that each exhibits aberrant synaptic transmission at the larval neuromuscular junction as a result of aberrant excitability of the motor neuron. In the present application, further functional and molecular characterization of these three genes is proposed. The phenotypes of flies lacking each gene, as well as overexpressing each gene, will be determined. Possible synergistic interactions among the genes will be tested by construction and analysis of double mutants. Effects of each gene on nerve terminal structure and electrophysiological properties will be determined. To facilitate cloning of these genes, mutagenesis with P-elements and X-rays will be performed. Isolation and sequence analysis of cDNAs from these genes will provide clues as to the function of the gene products and provide material for further studies. These genes might encode ion channel subunits or regulatory molecules such as protein kinases, G-proteins, or calcium binding proteins. Because such genes are well conserved in evolution, human homologues of these genes will likely exist and might be involved in hereditable disorders of the nervous or neuromuscular system. In addition, because potassium and calcium channel functions are required for non-neural processes such as the control of blood pressure, insulin release and the activation of T-lymphocytes, these human homologues might be defective in hereditable disorders of these processes as well. Therefore I expect that the study of ion channel structure and regulation in Drosophila will have general medical significance. In the future, this genetic approach will be used further to identify and analyze additional components that control the important process of synaptic transmission.