The midline protein regulates axon guidance by blocking the reiteration of neuroblast rows within the Drosophila ventral nerve cord.

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    • Source:
      Publisher: Public Library of Science Country of Publication: United States NLM ID: 101239074 Publication Model: Print-Electronic Cited Medium: Internet ISSN: 1553-7404 (Electronic) Linking ISSN: 15537390 NLM ISO Abbreviation: PLoS Genet Subsets: MEDLINE
    • Publication Information:
      Original Publication: San Francisco, CA : Public Library of Science, c2005-
    • Subject Terms:
    • Abstract:
      Guiding axon growth cones towards their targets is a fundamental process that occurs in a developing nervous system. Several major signaling systems are involved in axon-guidance, and disruption of these systems causes axon-guidance defects. However, the specific role of the environment in which axons navigate in regulating axon-guidance has not been examined in detail. In Drosophila, the ventral nerve cord is divided into segments, and half-segments and the precursor neuroblasts are formed in rows and columns in individual half-segments. The row-wise expression of segment-polarity genes within the neuroectoderm provides the initial row-wise identity to neuroblasts. Here, we show that in embryos mutant for the gene midline, which encodes a T-box DNA binding protein, row-2 neuroblasts and their neuroectoderm adopt a row-5 identity. This reiteration of row-5 ultimately creates a non-permissive zone or a barrier, which prevents the extension of interneuronal longitudinal tracts along their normal anterior-posterior path. While we do not know the nature of the barrier, the axon tracts either stall when they reach this region or project across the midline or towards the periphery along this zone. Previously, we had shown that midline ensures ancestry-dependent fate specification in a neuronal lineage. These results provide the molecular basis for the axon guidance defects in midline mutants and the significance of proper specification of the environment to axon-guidance. These results also reveal the importance of segmental polarity in guiding axons from one segment to the next, and a link between establishment of broad segmental identity and axon guidance.
      Competing Interests: The authors have declared that no competing interests exist.
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    • Grant Information:
      R01 GM080538 United States GM NIGMS NIH HHS
    • Accession Number:
      0 (Drosophila Proteins)
      0 (T-Box Domain Proteins)
      0 (mid protein, Drosophila)
    • Publication Date:
      Date Created: 20140104 Date Completed: 20140820 Latest Revision: 20211021
    • Publication Date:
      20240104
    • Accession Number:
      PMC3873230
    • Accession Number:
      10.1371/journal.pgen.1004050
    • Accession Number:
      24385932