title: Drosophila semaphorin2b is required for the axon guidance of a subset of embryonic neurons.
abstract: BACKGROUND
  The process of axon guidance is important in establishing functional neural circuits. The differential expression of cell-autonomous axon guidance factors is crucial for allowing axons of different neurons to take unique trajectories in response to spatially and temporally restricted cell non-autonomous axon guidance factors. A key motivation in the field is to provide adequate explanations for axon behavior with respect to the differential expression of these factors.
  
  
  RESULTS
  We report the characterization of a predicted secreted semaphorin family member, semaphorin2b (Sema-2b) in Drosophila embryonic axon guidance. Misexpression of Sema-2b in neurons causes highly penetrant axon guidance phenotypes in specific longitudinal and motoneuron pathways; however, expression of Sema-2b in muscles traversed by these motoneurons has no effect on axon guidance. In Sema-2b loss-of-function embryos, specific motoneuron and interneuron axon pathways display guidance defects. Specific visualization of the neurons that normally express Sema-2b reveals that this neuronal cohort is strongly affected by Sema-2b loss-of-function alleles.
  
  
  CONCLUSIONS
  While secreted semaphorins have been implicated as cell non-autonomous chemorepellants in a variety of contexts, here we report previously undescribed Sema-2b loss-of-function and misexpression phenotypes that are consistent with a cell-autonomous role for Sema-2b.
authors.affiliation: Department of Cell Biology and Program in Neuroscience, Harvard Medical School, Boston, Massachusetts 02115, USA.
authors.forename: Mark M
authors.initials: MM
authors.lastname: Emerson
authors.forename: Jennifer B
authors.initials: JB
authors.lastname: Long
authors.forename: David
authors.initials: D
authors.lastname: Van Vactor
mesh_terms: D000818:Animals; D001369:Axons / Q000378:metabolism; D004330:Drosophila / Q000196:embryology* / Q000378:metabolism*; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental / Q000235:genetics / Q000502:physiology; D009474:Neurons / Q000166:cytology* / Q000378:metabolism*; D039961:Semaphorins / Q000235:genetics / Q000378:metabolism*
chemical_list: D029721:Drosophila Proteins; D039961:Semaphorins