title: Midline crossing by gustatory receptor neuron axons is regulated by fruitless, doublesex and the Roundabout receptors.
abstract: Although nervous system sexual dimorphisms are known in many species, relatively little is understood about the molecular mechanisms generating these dimorphisms. Recent findings in Drosophila provide the tools for dissecting how neurogenesis and neuronal differentiation are modulated by the Drosophila sex-determination regulatory genes to produce nervous system sexual dimorphisms. Here we report studies aimed at illuminating the basis of the sexual dimorphic axonal projection patterns of foreleg gustatory receptor neurons (GRNs): only in males do GRN axons project across the midline of the ventral nerve cord. We show that the sex determination genes fruitless (fru) and doublesex (dsx) both contribute to establishing this sexual dimorphism. Male-specific Fru (Fru(M)) acts in foreleg GRNs to promote midline crossing by their axons, whereas midline crossing is repressed in females by female-specific Dsx (Dsx(F)). In addition, midline crossing by these neurons might be promoted in males by male-specific Dsx (Dsx(M)). Finally, we (1) demonstrate that the roundabout (robo) paralogs also regulate midline crossing by these neurons, and (2) provide evidence that Fru(M) exerts its effect on midline crossing by directly or indirectly regulating Robo signaling.
authors.affiliation: Department of Biology, Stanford University, Stanford, CA 94305, USA. mellertd@janelia.hhmi.org
authors.forename: David J
authors.initials: DJ
authors.lastname: Mellert
authors.forename: Jon-Michael
authors.initials: JM
authors.lastname: Knapp
authors.forename: Devanand S
authors.initials: DS
authors.lastname: Manoli
authors.forename: Geoffrey W
authors.initials: GW
authors.lastname: Meissner
authors.forename: Bruce S
authors.initials: BS
authors.lastname: Baker
mesh_terms: D000818:Animals; D001369:Axons / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000201:enzymology / Q000378:metabolism*; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D018613:Microscopy, Confocal; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000378:metabolism*; D011971:Receptors, Immunologic / Q000235:genetics / Q000378:metabolism*; D012727:Sex Characteristics; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D000097905:Roundabout Proteins
chemical_list: D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D009419:Nerve Tissue Proteins; D011956:Receptors, Cell Surface; D011971:Receptors, Immunologic; D014157:Transcription Factors; D000097905:Roundabout Proteins; C070369:DSX protein, Drosophila; C103226:fru protein, Drosophila; C405956:gustatory receptor, Drosophila