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Axon-Schwann cell interactions during peripheral nerve regeneration in zebrafish larvae.

Ceci ML, Mardones-Krsulovic C, Sánchez M, Valdivia LE, Allende ML - Neural Dev (2014)

Bottom Line: Furthermore, Schwann cells are required for directional extension and fasciculation of the regenerating nerve.We provide evidence that these cells and regrowing axons are mutually dependant during early stages of nerve regeneration in the pLL.The accessibility of the pLL nerve and the availability of transgenic lines that label this structure and their synaptic targets provides an outstanding in vivo model to study the different events associated with axonal extension, target reinnervation, and the complex cellular interactions between glial cells and injured axons during nerve regeneration.

View Article: PubMed Central - HTML - PubMed

Affiliation: FONDAP Center for Genome Regulation, Facultad de Ciencias, Universidad de Chile, Casilla 653, Santiago, Chile. allende@uchile.cl.

ABSTRACT

Background: Peripheral nerve injuries can severely affect the way that animals perceive signals from the surrounding environment. While damage to peripheral axons generally has a better outcome than injuries to central nervous system axons, it is currently unknown how neurons re-establish their target innervations to recover function after injury, and how accessory cells contribute to this task. Here we use a simple technique to create reproducible and localized injury in the posterior lateral line (pLL) nerve of zebrafish and follow the fate of both neurons and Schwann cells.

Results: Using pLL single axon labeling by transient transgene expression, as well as transplantation of glial precursor cells in zebrafish larvae, we individualize different components in this system and characterize their cellular behaviors during the regenerative process. Neurectomy is followed by loss of Schwann cell differentiation markers that is reverted after nerve regrowth. We show that reinnervation of lateral line hair cells in neuromasts during pLL nerve regeneration is a highly dynamic process with promiscuous yet non-random target recognition. Furthermore, Schwann cells are required for directional extension and fasciculation of the regenerating nerve. We provide evidence that these cells and regrowing axons are mutually dependant during early stages of nerve regeneration in the pLL. The role of ErbB signaling in this context is also explored.

Conclusion: The accessibility of the pLL nerve and the availability of transgenic lines that label this structure and their synaptic targets provides an outstanding in vivo model to study the different events associated with axonal extension, target reinnervation, and the complex cellular interactions between glial cells and injured axons during nerve regeneration.

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Impairment of Schwann cell migration following treatment with AG1478. (A) Normal distribution of Schwann cells in a 3 dpf control foxD3:GFP larva. (B) Total absence of Schwann cells in 3 dpf foxD3:GFP/Cxcr4:mCherry larvae treated with 5 μM AG1478 from 10 to 58 hpf (in this double transgenic, neuromasts are labeled in red fluorescence and Schwann cells in green). The supernumerary neuromasts that form in the absence of glial cells are indicated by arrowheads. (C) Partial absence of Schwann cells in 3 dpf foxD3:GFP larvae treated with 3.5 μM AG1478 from 24 to 58 hpf. With this treatement the Schwann cells migrate as far as the posterior end of the trunk (±two somites), but not into the tail at 3 dpf. Scale: A-C: 100 μm.
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Figure 7: Impairment of Schwann cell migration following treatment with AG1478. (A) Normal distribution of Schwann cells in a 3 dpf control foxD3:GFP larva. (B) Total absence of Schwann cells in 3 dpf foxD3:GFP/Cxcr4:mCherry larvae treated with 5 μM AG1478 from 10 to 58 hpf (in this double transgenic, neuromasts are labeled in red fluorescence and Schwann cells in green). The supernumerary neuromasts that form in the absence of glial cells are indicated by arrowheads. (C) Partial absence of Schwann cells in 3 dpf foxD3:GFP larvae treated with 3.5 μM AG1478 from 24 to 58 hpf. With this treatement the Schwann cells migrate as far as the posterior end of the trunk (±two somites), but not into the tail at 3 dpf. Scale: A-C: 100 μm.

Mentions: First, we interfered with migration of Schwann cell precursors during their development by incubating larvae with AG1478. This drug effectively depletes peripheral nerves of Schwann cells if administered prior to the beginning of their migration along the growing pLL nerve[61]. Incubation of embryos between 10 hpf and 58 hpf with 5 μM AG1478 completely eliminated all Schwann cells, as expected (Figure 7A). We confirmed that Schwann cells were effectively absent by the appearance of supernumerary neuromasts, as has been reported[38] (Figure 7B, arrowheads). Additionally, incubation of the larvae with 3.5 μM AG1478 between 24 hpf and 58 hpf, allowed normal development of Schwann cells as far as the posterior trunk but prevented their development in the tail (Figure 7C). Twelve hours before neurectomy, we washed out the inhibitor in order to avoid any interference of the drug on pLL nerve regeneration.


Axon-Schwann cell interactions during peripheral nerve regeneration in zebrafish larvae.

Ceci ML, Mardones-Krsulovic C, Sánchez M, Valdivia LE, Allende ML - Neural Dev (2014)

Impairment of Schwann cell migration following treatment with AG1478. (A) Normal distribution of Schwann cells in a 3 dpf control foxD3:GFP larva. (B) Total absence of Schwann cells in 3 dpf foxD3:GFP/Cxcr4:mCherry larvae treated with 5 μM AG1478 from 10 to 58 hpf (in this double transgenic, neuromasts are labeled in red fluorescence and Schwann cells in green). The supernumerary neuromasts that form in the absence of glial cells are indicated by arrowheads. (C) Partial absence of Schwann cells in 3 dpf foxD3:GFP larvae treated with 3.5 μM AG1478 from 24 to 58 hpf. With this treatement the Schwann cells migrate as far as the posterior end of the trunk (±two somites), but not into the tail at 3 dpf. Scale: A-C: 100 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4214607&req=5

Figure 7: Impairment of Schwann cell migration following treatment with AG1478. (A) Normal distribution of Schwann cells in a 3 dpf control foxD3:GFP larva. (B) Total absence of Schwann cells in 3 dpf foxD3:GFP/Cxcr4:mCherry larvae treated with 5 μM AG1478 from 10 to 58 hpf (in this double transgenic, neuromasts are labeled in red fluorescence and Schwann cells in green). The supernumerary neuromasts that form in the absence of glial cells are indicated by arrowheads. (C) Partial absence of Schwann cells in 3 dpf foxD3:GFP larvae treated with 3.5 μM AG1478 from 24 to 58 hpf. With this treatement the Schwann cells migrate as far as the posterior end of the trunk (±two somites), but not into the tail at 3 dpf. Scale: A-C: 100 μm.
Mentions: First, we interfered with migration of Schwann cell precursors during their development by incubating larvae with AG1478. This drug effectively depletes peripheral nerves of Schwann cells if administered prior to the beginning of their migration along the growing pLL nerve[61]. Incubation of embryos between 10 hpf and 58 hpf with 5 μM AG1478 completely eliminated all Schwann cells, as expected (Figure 7A). We confirmed that Schwann cells were effectively absent by the appearance of supernumerary neuromasts, as has been reported[38] (Figure 7B, arrowheads). Additionally, incubation of the larvae with 3.5 μM AG1478 between 24 hpf and 58 hpf, allowed normal development of Schwann cells as far as the posterior trunk but prevented their development in the tail (Figure 7C). Twelve hours before neurectomy, we washed out the inhibitor in order to avoid any interference of the drug on pLL nerve regeneration.

Bottom Line: Furthermore, Schwann cells are required for directional extension and fasciculation of the regenerating nerve.We provide evidence that these cells and regrowing axons are mutually dependant during early stages of nerve regeneration in the pLL.The accessibility of the pLL nerve and the availability of transgenic lines that label this structure and their synaptic targets provides an outstanding in vivo model to study the different events associated with axonal extension, target reinnervation, and the complex cellular interactions between glial cells and injured axons during nerve regeneration.

View Article: PubMed Central - HTML - PubMed

Affiliation: FONDAP Center for Genome Regulation, Facultad de Ciencias, Universidad de Chile, Casilla 653, Santiago, Chile. allende@uchile.cl.

ABSTRACT

Background: Peripheral nerve injuries can severely affect the way that animals perceive signals from the surrounding environment. While damage to peripheral axons generally has a better outcome than injuries to central nervous system axons, it is currently unknown how neurons re-establish their target innervations to recover function after injury, and how accessory cells contribute to this task. Here we use a simple technique to create reproducible and localized injury in the posterior lateral line (pLL) nerve of zebrafish and follow the fate of both neurons and Schwann cells.

Results: Using pLL single axon labeling by transient transgene expression, as well as transplantation of glial precursor cells in zebrafish larvae, we individualize different components in this system and characterize their cellular behaviors during the regenerative process. Neurectomy is followed by loss of Schwann cell differentiation markers that is reverted after nerve regrowth. We show that reinnervation of lateral line hair cells in neuromasts during pLL nerve regeneration is a highly dynamic process with promiscuous yet non-random target recognition. Furthermore, Schwann cells are required for directional extension and fasciculation of the regenerating nerve. We provide evidence that these cells and regrowing axons are mutually dependant during early stages of nerve regeneration in the pLL. The role of ErbB signaling in this context is also explored.

Conclusion: The accessibility of the pLL nerve and the availability of transgenic lines that label this structure and their synaptic targets provides an outstanding in vivo model to study the different events associated with axonal extension, target reinnervation, and the complex cellular interactions between glial cells and injured axons during nerve regeneration.

Show MeSH
Related in: MedlinePlus