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Cell biology in neuroscience: Architects in neural circuit design: glia control neuron numbers and connectivity.

Corty MM, Freeman MR - J. Cell Biol. (2013)

Bottom Line: Glia serve many important functions in the mature nervous system.In addition, these diverse cells have emerged as essential participants in nearly all aspects of neural development.Recent findings illustrate the importance of glial cells in shaping the nervous system by controlling the number and connectivity of neurons.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Neurobiology, University of Massachusetts Medical School, Howard Hughes Medical Institute, Worcester, MA 01605.

ABSTRACT
Glia serve many important functions in the mature nervous system. In addition, these diverse cells have emerged as essential participants in nearly all aspects of neural development. Improved techniques to study neurons in the absence of glia, and to visualize and manipulate glia in vivo, have greatly expanded our knowledge of glial biology and neuron-glia interactions during development. Exciting studies in the last decade have begun to identify the cellular and molecular mechanisms by which glia exert control over neuronal circuit formation. Recent findings illustrate the importance of glial cells in shaping the nervous system by controlling the number and connectivity of neurons.

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Developmental pruning of mushroom body γ-neuron axons requires glia. (A) Before metamorphosis, cortex and astrocyte-like glia secrete the TGF-β ligand Myoglianin, which acts through γ-neuron baboon receptors to up-regulate expression of the ecdysone receptor EcR-B1. This makes γ-neurons competent to respond to the ecdysone pulse that will initiate pruning. (B) As metamorphosis begins, glia infiltrate the mushroom body neuropil. This infiltration is dependent on the glial cell surface receptor Draper. Arrival of glia coincides with axon blebbing and fragmentation, but it remains uncertain whether glia actively promote this fragmentation. (C) Glia are required for clearance of axonal debris. Recognition and phagocytosis of the debris is also mediated by the glial cell surface receptor Draper.
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fig2: Developmental pruning of mushroom body γ-neuron axons requires glia. (A) Before metamorphosis, cortex and astrocyte-like glia secrete the TGF-β ligand Myoglianin, which acts through γ-neuron baboon receptors to up-regulate expression of the ecdysone receptor EcR-B1. This makes γ-neurons competent to respond to the ecdysone pulse that will initiate pruning. (B) As metamorphosis begins, glia infiltrate the mushroom body neuropil. This infiltration is dependent on the glial cell surface receptor Draper. Arrival of glia coincides with axon blebbing and fragmentation, but it remains uncertain whether glia actively promote this fragmentation. (C) Glia are required for clearance of axonal debris. Recognition and phagocytosis of the debris is also mediated by the glial cell surface receptor Draper.

Mentions: In Drosophila, axon pruning during metamorphosis is important for the remodeling required to form mature adult circuits. Mushroom body γ-neurons prune their larval axons during early metamorphosis, followed by formation of new adult-specific connections as metamorphosis continues (Fig. 2; Lee et al., 1999). In addition to many cell-autonomous requirements for proper axon pruning, there are multiple essential roles for neighboring glia in mediating axon removal in this circuit. Initiation of pruning is triggered by a pulse of the molting hormone ecdysone just before metamorphosis (Lee et al., 2000). γ-Neuron responsiveness to this critical signal is controlled by surrounding cortex and astrocyte-like glia, which express the TGF-β ligand Myoglianin (Myo) during late larval stages (Awasaki et al., 2011). Glial-derived Myo must activate TGF-β signaling within γ-neurons to up-regulate expression of the ecdysone receptor B1 isoform (EcR-B1) so that γ-neurons can receive the hormonal signal that will trigger pruning (Zheng et al., 2003; Awasaki et al., 2011). Myo therefore represents perhaps the first glial-derived factor required for neurons to become competent to prune their axons (Fig. 2 A).


Cell biology in neuroscience: Architects in neural circuit design: glia control neuron numbers and connectivity.

Corty MM, Freeman MR - J. Cell Biol. (2013)

Developmental pruning of mushroom body γ-neuron axons requires glia. (A) Before metamorphosis, cortex and astrocyte-like glia secrete the TGF-β ligand Myoglianin, which acts through γ-neuron baboon receptors to up-regulate expression of the ecdysone receptor EcR-B1. This makes γ-neurons competent to respond to the ecdysone pulse that will initiate pruning. (B) As metamorphosis begins, glia infiltrate the mushroom body neuropil. This infiltration is dependent on the glial cell surface receptor Draper. Arrival of glia coincides with axon blebbing and fragmentation, but it remains uncertain whether glia actively promote this fragmentation. (C) Glia are required for clearance of axonal debris. Recognition and phagocytosis of the debris is also mediated by the glial cell surface receptor Draper.
© Copyright Policy - openaccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC3824021&req=5

fig2: Developmental pruning of mushroom body γ-neuron axons requires glia. (A) Before metamorphosis, cortex and astrocyte-like glia secrete the TGF-β ligand Myoglianin, which acts through γ-neuron baboon receptors to up-regulate expression of the ecdysone receptor EcR-B1. This makes γ-neurons competent to respond to the ecdysone pulse that will initiate pruning. (B) As metamorphosis begins, glia infiltrate the mushroom body neuropil. This infiltration is dependent on the glial cell surface receptor Draper. Arrival of glia coincides with axon blebbing and fragmentation, but it remains uncertain whether glia actively promote this fragmentation. (C) Glia are required for clearance of axonal debris. Recognition and phagocytosis of the debris is also mediated by the glial cell surface receptor Draper.
Mentions: In Drosophila, axon pruning during metamorphosis is important for the remodeling required to form mature adult circuits. Mushroom body γ-neurons prune their larval axons during early metamorphosis, followed by formation of new adult-specific connections as metamorphosis continues (Fig. 2; Lee et al., 1999). In addition to many cell-autonomous requirements for proper axon pruning, there are multiple essential roles for neighboring glia in mediating axon removal in this circuit. Initiation of pruning is triggered by a pulse of the molting hormone ecdysone just before metamorphosis (Lee et al., 2000). γ-Neuron responsiveness to this critical signal is controlled by surrounding cortex and astrocyte-like glia, which express the TGF-β ligand Myoglianin (Myo) during late larval stages (Awasaki et al., 2011). Glial-derived Myo must activate TGF-β signaling within γ-neurons to up-regulate expression of the ecdysone receptor B1 isoform (EcR-B1) so that γ-neurons can receive the hormonal signal that will trigger pruning (Zheng et al., 2003; Awasaki et al., 2011). Myo therefore represents perhaps the first glial-derived factor required for neurons to become competent to prune their axons (Fig. 2 A).

Bottom Line: Glia serve many important functions in the mature nervous system.In addition, these diverse cells have emerged as essential participants in nearly all aspects of neural development.Recent findings illustrate the importance of glial cells in shaping the nervous system by controlling the number and connectivity of neurons.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Neurobiology, University of Massachusetts Medical School, Howard Hughes Medical Institute, Worcester, MA 01605.

ABSTRACT
Glia serve many important functions in the mature nervous system. In addition, these diverse cells have emerged as essential participants in nearly all aspects of neural development. Improved techniques to study neurons in the absence of glia, and to visualize and manipulate glia in vivo, have greatly expanded our knowledge of glial biology and neuron-glia interactions during development. Exciting studies in the last decade have begun to identify the cellular and molecular mechanisms by which glia exert control over neuronal circuit formation. Recent findings illustrate the importance of glial cells in shaping the nervous system by controlling the number and connectivity of neurons.

Show MeSH
Related in: MedlinePlus