title: Linking cell fate, trajectory choice, and target selection: genetic analysis of Sema-2b in olfactory axon targeting.
abstract: Neural circuit assembly requires selection of specific cell fates, axonal trajectories, and synaptic targets. By analyzing the function of a secreted semaphorin, Sema-2b, in Drosophila olfactory receptor neuron (ORN) development, we identified multiple molecular and cellular mechanisms that link these events. Notch signaling limits Sema-2b expression to ventromedial ORN classes, within which Sema-2b cell-autonomously sensitizes ORN axons to external semaphorins. Central-brain-derived Sema-2a and Sema-2b attract Sema-2b-expressing axons to the ventromedial trajectory. In addition, Sema-2b/PlexB-mediated axon-axon interactions consolidate this trajectory choice and promote ventromedial axon-bundle formation. Selecting the correct developmental trajectory is ultimately essential for proper target choice. These findings demonstrate that Sema-2b couples ORN axon guidance to postsynaptic target neuron dendrite patterning well before the final target selection phase, and exemplify how a single guidance molecule can drive consecutive stages of neural circuit assembly with the help of sophisticated spatial and temporal regulation.
authors.affiliation: Howard Hughes Medical Institute and Department of Biology, Stanford University, Stanford, CA 94305, USA.
authors.forename: William J
authors.initials: WJ
authors.lastname: Joo
authors.forename: Lora B
authors.initials: LB
authors.lastname: Sweeney
authors.forename: Liang
authors.initials: L
authors.lastname: Liang
authors.forename: Liqun
authors.initials: L
authors.lastname: Luo
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D001369:Axons / Q000502:physiology*; D004330:Drosophila; D029721:Drosophila Proteins / Q000235:genetics* / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D020439:Growth Cones / Q000502:physiology; D019581:Neuropil / Q000166:cytology* / Q000378:metabolism; D009830:Olfactory Bulb / Q000166:cytology / Q000378:metabolism; D009833:Olfactory Pathways / Q000166:cytology*; D018034:Olfactory Receptor Neurons / Q000254:growth & development* / Q000378:metabolism; D021382:Protein Sorting Signals; D039961:Semaphorins / Q000235:genetics* / Q000378:metabolism
chemical_list: D029721:Drosophila Proteins; D021382:Protein Sorting Signals; D039961:Semaphorins