A gain-of-function screen for genes that influence axon guidance identifies the NF-kappaB protein dorsal and reveals a requirement for the kinase Pelle in Drosophila photoreceptor axon targeting.
To identify novel regulators of nervous system development, we used the GAL4-UAS misexpression system in Drosophila to screen for genes that influence axon guidance in developing embryos. We mobilized the Gene Search (GS) P element and identified 42 lines with insertions in unique loci, including leak/roundabout2, which encodes an axon guidance receptor and confirms the utility of our screen. The genes we identified encode proteins of diverse classes, some acting near the cell surface and others in the cytoplasm or nucleus. We found that one GS line drove misexpression of the NF-kappaB transcription factor Dorsal, causing motor axons to bypass their correct termination sites. In the developing visual system, Dorsal misexpression also caused photoreceptor axons to reach incorrect positions within the optic lobe. This mistargeting occurred without observable changes of cell fate and correlated with localization of ectopic Dorsal in distal axons. We found that Dorsal and its inhibitor Cactus are expressed in photoreceptors, though neither was required for axon targeting. However, mutation analyses of genes known to act upstream of Dorsal revealed a requirement for the interleukin receptor-associated kinase family kinase Pelle for layer-specific targeting of photoreceptor axons, validating our screen as a means to identify new molecular determinants of nervous system development in vivo.
Mindorff
Elizabeth N
EN
Graduate Program in Neurological Sciences, McGill University, Montreal, Quebec, Canada.
O'Keefe
David D
DD
Labbé
Alain
A
Yang
Jennie Ping
JP
Ou
Yimiao
Y
Yoshikawa
Shingo
S
van Meyel
Donald J
DJ
D000818:Animals; D001369:Axons / Q000378:metabolism* / Q000648:ultrastructure; D001483:Base Sequence; D017931:DNA Primers / Q000235:genetics; D029721:Drosophila Proteins / Q000235:genetics* / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000196:embryology / Q000235:genetics* / Q000378:metabolism*; D005260:Female; D017344:Genes, Insect; D008297:Male; D009046:Motor Neurons / Q000166:cytology / Q000378:metabolism; D009154:Mutation; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism*; D010641:Phenotype; D010750:Phosphoproteins / Q000235:genetics* / Q000378:metabolism*; D017956:Photoreceptor Cells, Invertebrate / Q000196:embryology / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000235:genetics* / Q000378:metabolism*; D015398:Signal Transduction / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism*
D017931:DNA Primers; D029721:Drosophila Proteins; D016328:NF-kappa B; D009687:Nuclear Proteins; D010750:Phosphoproteins; D014157:Transcription Factors; C062236:dl protein, Drosophila; C079896:pll protein, Drosophila; D017346:Protein Serine-Threonine Kinases