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Drosophila Neuronal Injury Follows a Temporal Sequence of Cellular Events Leading to Degeneration at the Neuromuscular Junction.

Lincoln BL, Alabsi SH, Frendo N, Freund R, Keller LC - J Exp Neurosci (2015)

Bottom Line: At the molecular level, neurodegeneration involves the activation of complex signaling pathways that drive the active destruction of neurons and their intracellular components.Our data provide insights into the early molecular events that occur during axonal and neuromuscular degeneration in a genetically tractable model organism.Importantly, the mechanisms that mediate neurodegeneration in flies are conserved in humans.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Sciences, Quinnipiac University, Hamden, CT, USA.

ABSTRACT
Neurodegenerative diseases affect millions of people worldwide, and as the global population ages, there is a critical need to improve our understanding of the molecular and cellular mechanisms that drive neurodegeneration. At the molecular level, neurodegeneration involves the activation of complex signaling pathways that drive the active destruction of neurons and their intracellular components. Here, we use an in vivo motor neuron injury assay to acutely induce neurodegeneration in order to follow the temporal order of events that occur following injury in Drosophila melanogaster. We find that sites of injury can be rapidly identified based on structural defects to the neuronal cytoskeleton that result in disrupted axonal transport. Additionally, the neuromuscular junction accumulates ubiquitinated proteins prior to the neurodegenerative events, occurring at 24 hours post injury. Our data provide insights into the early molecular events that occur during axonal and neuromuscular degeneration in a genetically tractable model organism. Importantly, the mechanisms that mediate neurodegeneration in flies are conserved in humans. Thus, these studies have implications for our understanding of the cellular and molecular events that occur in humans and will facilitate the identification of biomedically relevant targets for future treatments.

No MeSH data available.


Related in: MedlinePlus

Injury to motor neuron axons induces a significant increase in ubiquitinated proteins at the NMJ. (A) The NMJs at muscle 6/7 in uninjured third instar larvae show well-defined neuronal membranes stained with HRP (red, middle panel) and very few accumulations of ubiquitinated proteins stained with FK2 (green, bottom panel). (B) Approximately 12 hours after neuronal injury, animals appear to have disrupted neuronal membranes (red, middle panel) and accumulations of ubiquitinated proteins at the NMJs of muscle 6/7 (green, bottom panel). (C) The number of FK2-positive puncta at each NMJ of muscle 6/7 was significantly increased 12 hours postneuronal injury from 0.1923 (n = 13 NMJs) to 6.55 (n = 20 NMJs; P < 0.0001). Error bars represent SEM. Scale bar = 10 μm.
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f5-jen-suppl.2-2015-001: Injury to motor neuron axons induces a significant increase in ubiquitinated proteins at the NMJ. (A) The NMJs at muscle 6/7 in uninjured third instar larvae show well-defined neuronal membranes stained with HRP (red, middle panel) and very few accumulations of ubiquitinated proteins stained with FK2 (green, bottom panel). (B) Approximately 12 hours after neuronal injury, animals appear to have disrupted neuronal membranes (red, middle panel) and accumulations of ubiquitinated proteins at the NMJs of muscle 6/7 (green, bottom panel). (C) The number of FK2-positive puncta at each NMJ of muscle 6/7 was significantly increased 12 hours postneuronal injury from 0.1923 (n = 13 NMJs) to 6.55 (n = 20 NMJs; P < 0.0001). Error bars represent SEM. Scale bar = 10 μm.

Mentions: Ubiquitinated protein accumulations have long been known to be associated with neurodegenerative diseases.34 We sought to examine if neuronal injury of Drosophila motor neurons could induce increases in the amount of ubiquitinated proteins at the NMJ using an antibody (α-FK2) against both mono-and poly-ubiquitinated proteins. Quantification of numbers of FK2-positive puncta within the NMJ at muscle 6/7 revealed a significant increase 12 hours post injury. Uninjured larval NMJs contained an average of 0.19 puncta per synapse (n = 13 NMJs), whereas injured larvae had an average of 6.55 puncta per synapse (n = 20 NMJs; Fig. 5; P < 0.0001). These data are consistent with previous reports of autopsies from various human spinal cord traumas signifying that ubiquitin accumulations mark an early event in neuronal injury.33


Drosophila Neuronal Injury Follows a Temporal Sequence of Cellular Events Leading to Degeneration at the Neuromuscular Junction.

Lincoln BL, Alabsi SH, Frendo N, Freund R, Keller LC - J Exp Neurosci (2015)

Injury to motor neuron axons induces a significant increase in ubiquitinated proteins at the NMJ. (A) The NMJs at muscle 6/7 in uninjured third instar larvae show well-defined neuronal membranes stained with HRP (red, middle panel) and very few accumulations of ubiquitinated proteins stained with FK2 (green, bottom panel). (B) Approximately 12 hours after neuronal injury, animals appear to have disrupted neuronal membranes (red, middle panel) and accumulations of ubiquitinated proteins at the NMJs of muscle 6/7 (green, bottom panel). (C) The number of FK2-positive puncta at each NMJ of muscle 6/7 was significantly increased 12 hours postneuronal injury from 0.1923 (n = 13 NMJs) to 6.55 (n = 20 NMJs; P < 0.0001). Error bars represent SEM. Scale bar = 10 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

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f5-jen-suppl.2-2015-001: Injury to motor neuron axons induces a significant increase in ubiquitinated proteins at the NMJ. (A) The NMJs at muscle 6/7 in uninjured third instar larvae show well-defined neuronal membranes stained with HRP (red, middle panel) and very few accumulations of ubiquitinated proteins stained with FK2 (green, bottom panel). (B) Approximately 12 hours after neuronal injury, animals appear to have disrupted neuronal membranes (red, middle panel) and accumulations of ubiquitinated proteins at the NMJs of muscle 6/7 (green, bottom panel). (C) The number of FK2-positive puncta at each NMJ of muscle 6/7 was significantly increased 12 hours postneuronal injury from 0.1923 (n = 13 NMJs) to 6.55 (n = 20 NMJs; P < 0.0001). Error bars represent SEM. Scale bar = 10 μm.
Mentions: Ubiquitinated protein accumulations have long been known to be associated with neurodegenerative diseases.34 We sought to examine if neuronal injury of Drosophila motor neurons could induce increases in the amount of ubiquitinated proteins at the NMJ using an antibody (α-FK2) against both mono-and poly-ubiquitinated proteins. Quantification of numbers of FK2-positive puncta within the NMJ at muscle 6/7 revealed a significant increase 12 hours post injury. Uninjured larval NMJs contained an average of 0.19 puncta per synapse (n = 13 NMJs), whereas injured larvae had an average of 6.55 puncta per synapse (n = 20 NMJs; Fig. 5; P < 0.0001). These data are consistent with previous reports of autopsies from various human spinal cord traumas signifying that ubiquitin accumulations mark an early event in neuronal injury.33

Bottom Line: At the molecular level, neurodegeneration involves the activation of complex signaling pathways that drive the active destruction of neurons and their intracellular components.Our data provide insights into the early molecular events that occur during axonal and neuromuscular degeneration in a genetically tractable model organism.Importantly, the mechanisms that mediate neurodegeneration in flies are conserved in humans.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Sciences, Quinnipiac University, Hamden, CT, USA.

ABSTRACT
Neurodegenerative diseases affect millions of people worldwide, and as the global population ages, there is a critical need to improve our understanding of the molecular and cellular mechanisms that drive neurodegeneration. At the molecular level, neurodegeneration involves the activation of complex signaling pathways that drive the active destruction of neurons and their intracellular components. Here, we use an in vivo motor neuron injury assay to acutely induce neurodegeneration in order to follow the temporal order of events that occur following injury in Drosophila melanogaster. We find that sites of injury can be rapidly identified based on structural defects to the neuronal cytoskeleton that result in disrupted axonal transport. Additionally, the neuromuscular junction accumulates ubiquitinated proteins prior to the neurodegenerative events, occurring at 24 hours post injury. Our data provide insights into the early molecular events that occur during axonal and neuromuscular degeneration in a genetically tractable model organism. Importantly, the mechanisms that mediate neurodegeneration in flies are conserved in humans. Thus, these studies have implications for our understanding of the cellular and molecular events that occur in humans and will facilitate the identification of biomedically relevant targets for future treatments.

No MeSH data available.


Related in: MedlinePlus