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In vivo characterization of microglial engulfment of dying neurons in the zebrafish spinal cord.

Morsch M, Radford R, Lee A, Don EK, Badrock AP, Hall TE, Cole NJ, Chung R - Front Cell Neurosci (2015)

Bottom Line: In vivo imaging confirmed the motile nature of microglia within the uninjured spinal cord.This process of microglial engulfment is highly dynamic, involving the extension of processes toward the lesion site and consequently the ingestion of the dying neuron. 3D rendering analysis of time-lapse recordings revealed the formation of phagosome-like structures in the activated microglia located at the site of neuronal ablation.This real-time representation of microglial phagocytosis in the living zebrafish spinal cord provides novel opportunities to study the mechanisms of microglia-mediated neuronal clearance.

View Article: PubMed Central - PubMed

Affiliation: Motor Neuron Disease Research Group, Faculty of Medicine and Health Sciences, Macquarie University Sydney, NSW, Australia.

ABSTRACT
Microglia are specialized phagocytes in the vertebrate central nervous system (CNS). As the resident immune cells of the CNS they play an important role in the removal of dying neurons during both development and in several neuronal pathologies. Microglia have been shown to prevent the diffusion of damaging degradation products of dying neurons by engulfment and ingestion. Here we describe a live imaging approach that uses UV laser ablation to selectively stress and kill spinal neurons and visualize the clearance of neuronal remnants by microglia in the zebrafish spinal cord. In vivo imaging confirmed the motile nature of microglia within the uninjured spinal cord. However, selective neuronal ablation triggered rapid activation of microglia, leading to phagocytic uptake of neuronal debris by microglia within 20-30 min. This process of microglial engulfment is highly dynamic, involving the extension of processes toward the lesion site and consequently the ingestion of the dying neuron. 3D rendering analysis of time-lapse recordings revealed the formation of phagosome-like structures in the activated microglia located at the site of neuronal ablation. This real-time representation of microglial phagocytosis in the living zebrafish spinal cord provides novel opportunities to study the mechanisms of microglia-mediated neuronal clearance.

No MeSH data available.


Related in: MedlinePlus

Accumulation of the apoptotic marker AnnexinV within microglia. Upon ablation of a neuron in the spinal cord (A; arrowhead) the surrounding microglia moved toward the ablation site (B). After several minutes the fluorescently labeled marker AnnexinV lights up within the microglia (C; arrow). AnnexinV accumulation within the microglia increases over time (D), till the phagocytic debris gets transported away from the ablation site (E) and conceivably degraded resulting in disappearance of the fluorescence (F). Scale bars = 20 μm. Supplementary Video 3 shows the time-lapse video of this process.
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Figure 5: Accumulation of the apoptotic marker AnnexinV within microglia. Upon ablation of a neuron in the spinal cord (A; arrowhead) the surrounding microglia moved toward the ablation site (B). After several minutes the fluorescently labeled marker AnnexinV lights up within the microglia (C; arrow). AnnexinV accumulation within the microglia increases over time (D), till the phagocytic debris gets transported away from the ablation site (E) and conceivably degraded resulting in disappearance of the fluorescence (F). Scale bars = 20 μm. Supplementary Video 3 shows the time-lapse video of this process.

Mentions: To specifically visualize the engulfment of neuronal remnants from dying neurons, we used a triple labeled fish (islet1:GFP; mpeg1:mCherry; ubiq:secAnnexinV-mVenus) to visualize this process following our UV ablation approach. AnnexinV-mVenus accumulated in the phagocytic vesicles of the activated microglia after neuronal ablation (Figure 5). Over a time frame of approximately 2 hours, AnnexinV accumulated within the cytoplasm of the microglial cell and subsequently was transported away from the ablation site.


In vivo characterization of microglial engulfment of dying neurons in the zebrafish spinal cord.

Morsch M, Radford R, Lee A, Don EK, Badrock AP, Hall TE, Cole NJ, Chung R - Front Cell Neurosci (2015)

Accumulation of the apoptotic marker AnnexinV within microglia. Upon ablation of a neuron in the spinal cord (A; arrowhead) the surrounding microglia moved toward the ablation site (B). After several minutes the fluorescently labeled marker AnnexinV lights up within the microglia (C; arrow). AnnexinV accumulation within the microglia increases over time (D), till the phagocytic debris gets transported away from the ablation site (E) and conceivably degraded resulting in disappearance of the fluorescence (F). Scale bars = 20 μm. Supplementary Video 3 shows the time-lapse video of this process.
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Related In: Results  -  Collection

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Figure 5: Accumulation of the apoptotic marker AnnexinV within microglia. Upon ablation of a neuron in the spinal cord (A; arrowhead) the surrounding microglia moved toward the ablation site (B). After several minutes the fluorescently labeled marker AnnexinV lights up within the microglia (C; arrow). AnnexinV accumulation within the microglia increases over time (D), till the phagocytic debris gets transported away from the ablation site (E) and conceivably degraded resulting in disappearance of the fluorescence (F). Scale bars = 20 μm. Supplementary Video 3 shows the time-lapse video of this process.
Mentions: To specifically visualize the engulfment of neuronal remnants from dying neurons, we used a triple labeled fish (islet1:GFP; mpeg1:mCherry; ubiq:secAnnexinV-mVenus) to visualize this process following our UV ablation approach. AnnexinV-mVenus accumulated in the phagocytic vesicles of the activated microglia after neuronal ablation (Figure 5). Over a time frame of approximately 2 hours, AnnexinV accumulated within the cytoplasm of the microglial cell and subsequently was transported away from the ablation site.

Bottom Line: In vivo imaging confirmed the motile nature of microglia within the uninjured spinal cord.This process of microglial engulfment is highly dynamic, involving the extension of processes toward the lesion site and consequently the ingestion of the dying neuron. 3D rendering analysis of time-lapse recordings revealed the formation of phagosome-like structures in the activated microglia located at the site of neuronal ablation.This real-time representation of microglial phagocytosis in the living zebrafish spinal cord provides novel opportunities to study the mechanisms of microglia-mediated neuronal clearance.

View Article: PubMed Central - PubMed

Affiliation: Motor Neuron Disease Research Group, Faculty of Medicine and Health Sciences, Macquarie University Sydney, NSW, Australia.

ABSTRACT
Microglia are specialized phagocytes in the vertebrate central nervous system (CNS). As the resident immune cells of the CNS they play an important role in the removal of dying neurons during both development and in several neuronal pathologies. Microglia have been shown to prevent the diffusion of damaging degradation products of dying neurons by engulfment and ingestion. Here we describe a live imaging approach that uses UV laser ablation to selectively stress and kill spinal neurons and visualize the clearance of neuronal remnants by microglia in the zebrafish spinal cord. In vivo imaging confirmed the motile nature of microglia within the uninjured spinal cord. However, selective neuronal ablation triggered rapid activation of microglia, leading to phagocytic uptake of neuronal debris by microglia within 20-30 min. This process of microglial engulfment is highly dynamic, involving the extension of processes toward the lesion site and consequently the ingestion of the dying neuron. 3D rendering analysis of time-lapse recordings revealed the formation of phagosome-like structures in the activated microglia located at the site of neuronal ablation. This real-time representation of microglial phagocytosis in the living zebrafish spinal cord provides novel opportunities to study the mechanisms of microglia-mediated neuronal clearance.

No MeSH data available.


Related in: MedlinePlus