Regulation of axon arborization pattern in the developing chick ciliary ganglion: Possible involvement of caspase 3

Hidetaka Katow, Teppei Kanaya, Tomohisa Ogawa, Ryo Egawa, Hiromu Yawo

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    1 Citation (Scopus)

    Abstract

    During a certain critical period in the development of the central and peripheral nervous systems, axonal branches and synapses are massively reorganized to form mature connections. In this process, neurons search their appropriate targets, expanding and/or retracting their axons. Recent work suggested that the caspase superfamily regulates the axon morphology. Here, we tested the hypothesis that caspase 3, which is one of the major executioners in apoptotic cell death, is involved in regulating the axon arborization. The embryonic chicken ciliary ganglion was used as a model system of synapse reorganization. A dominant negative mutant of caspase-3 precursor (C3DN) was made and overexpressed in presynaptic neurons in the midbrain to interfere with the intrinsic caspase-3 activity using an in ovo electroporation method. The axon arborization pattern was 3-dimensionally and quantitatively analyzed in the ciliary ganglion. The overexpression of C3DN significantly reduced the number of branching points, the branch order and the complexity index, whereas it significantly elongated the terminal branches at E6. It also increased the internodal distance significantly at E8. But, these effects were negligible at E10 or later. During E6–8, there appeared to be a dynamic balance in the axon arborization pattern between the “targeting” mode, which is accompanied by elongation of terminal branches and the pruning of collateral branches, and the “pathfinding” mode, which is accompanied by the retraction of terminal branches and the sprouting of new collateral branches. The local and transient activation of caspase 3 could direct the balance towards the pathfinding mode.

    Original languageEnglish
    Pages (from-to)115-128
    Number of pages14
    JournalDevelopment Growth and Differentiation
    Volume59
    Issue number3
    DOIs
    Publication statusPublished - 2017 Apr

    Keywords

    • axon growth
    • axon remodeling
    • caspase
    • electroporation
    • vertebrate embryo

    ASJC Scopus subject areas

    • Developmental Biology
    • Cell Biology

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