Dysregulation of axogenesis in the antennal nervous system of the embryonic grasshopper Schistocerca gregaria
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The antennal nervous system of the grasshopper Schistocerca gregaria features two parallel axon tracts each established early in embryogenesis by discrete pairs of pioneer neurons located at the antennal tip and whose growth cones contact so-called base pioneers en route to the brain. Here we present two antennal phenotypes in which a stereotypic dysregulation of axogenesis in a given tract is observed when only the base pioneer associated with that pathway is missing, consistent with a role for this cell type in guided axogenesis. Dysregulation involves defasciculation and aberrant navigation by pioneer axons resulting in a missing or depleted primordial antennal nerve to the brain. The dysregulated phenotypes reveal that axogenesis in each pathway is regulated independently. Previously unseen discrepancies in the navigational decisions made by pioneer neurons which derive sequentially from the same mother cell demonstrate that these progeny have separate identities. Possible mechanisms for the dysregulated phenotypes are considered.
KeywordsGrasshopper Embryo Antenna Pioneer neurons Axogenesis Dysregulation
We thank Dr. Tatjana Kleele for assistance with confocal imaging, Dr. Yu Liu for critical reading of an earlier manuscript, and two anonymous referees for their valuable insights. Both authors received financial support for this study from the Graduate School of Systemic Neuroscience, Biocenter, Ludwig-Maximilians-University of Munich.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no competing interests.
Human and animal rights
All experiments were performed in accordance with the guidelines for animal welfare as laid down by the Deutsche Forschungsgemeinschaft.
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