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Published March 20, 2001 | Supplemental Material
Journal Article Open

A gain-of-function screen for genes controlling motor axon guidance and synaptogenesis in Drosophila


Background: The neuromuscular system of the Drosophila larva contains a small number of identified motor neurons that make genetically defined synaptic connections with muscle fibers. We drove high-level expression of genes in these motor neurons by crossing 2293 GAL4-driven EP element lines with known insertion site sequences to lines containing a pan-neuronal GAL4 source and UAS-green fluorescent protein elements. This allowed visualization of every synapse in the neuromuscular system in live larvae. Results: We identified 114 EPs that generate axon guidance and/or synaptogenesis phenotypes in F1 EP x driver larvae. Analysis of genomic regions adjacent to these EPs defined 76 genes that exhibit neuromuscular gain-of-function phenotypes. Forty-one of these (known genes) have published mutant alleles; the other 35 (new genes) have not yet been characterized genetically. To assess the roles of the known genes, we surveyed published data on their phenotypes and expression patterns. We also examined loss-of-function mutants ourselves, identifying new guidance and synaptogenesis phenotypes for eight genes. At least three quarters of the known genes are important for nervous system development and/or function in wild-type flies. Conclusions: Known genes, new genes, and a set of previously analyzed genes with phenotypes in the Adh region display similar patterns of homology to sequences in other species and have equivalent EST representations. We infer from these results that most new genes will also have nervous system loss-of-function phenotypes. The proteins encoded by the 76 identified genes include GTPase regulators, vesicle trafficking proteins, kinases, and RNA binding proteins.

Additional Information

© 2001 Elsevier Science Ltd. Received 11 January 2001, Revised 8 February 2001, Accepted 8 February 2001, Available online 5 April 2001. We thank Violana Nesterova for excellent technical assistance; Cyrus Papan for creating the volume-rendered views of Figure 2; Erik Griffin for screening some of the X chromosome lines; Haig Keshishian for instruction in larval dissection and staining methods; Haig Keshishian and Barry Dickson for the UAS-GFP line; Marc Halfon for the UAS-2×-EGFP line; Todd Laverty (UC Berkeley) and Tom Kidd and Jason Melendez (Exelixis) for EP lines; Steve Crews, Inge The, Ken Howard, James DeZazzo, and the Bloomington Stock Center for mutant lines; Guochun Liao, Nomi Harris, and Sima Misra (BDGP) for information about EP flanking sequences and general assistance with databases; the BDGP, Flybase, and Celera Genomics, without whom this work would not have been possible; and Aloisia Schmid, Benno Schindelholz, Nina Sherwood, and Anna Salazar (Zinn group) for helpful discussions and comments on the manuscript. See http://www.caltech.edu/~zinn/ for further information on motor axons. R.K. was supported by an NRSA postdoctoral fellowship from the NIH. This work was supported by NIH grant NS28182 to K.Z.

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