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Mol Neurodegener. 2019 Jul 10;14(1):27. doi: 10.1186/s13024-019-0327-3.

Dynactin1 depletion leads to neuromuscular synapse instability and functional abnormalities.

Author information

1
Institut Curie, PSL Research University, INSERM U934, CNRS UMR3215, Sorbonne Université, F-75005, Paris, France.
2
Present Address: VIB-KU Leuven, Center for Brain & Disease Research, Leuven, Belgium.
3
Sorbonne Université, Inserm, CNRS, AP-HP, Institut du Cerveau et de la Moelle Épinière, ICM, F-75013, Paris, France.
4
Present Address: Zuckerman Mind Brain Behavior Institute, Columbia University, New York, USA.
5
Present Address: Center for Integrative Genomics, University of Lausanne, Lausanne, Switzerland.
6
Sorbonne Université, Inserm, CNRS, AP-HP, Institut du Cerveau et de la Moelle Épinière, ICM, F-75013, Paris, France. claire.wyart@icm-institute.org.
7
Institut Curie, PSL Research University, INSERM U934, CNRS UMR3215, Sorbonne Université, F-75005, Paris, France. filippo.del-bene@curie.fr.

Abstract

BACKGROUND:

Dynactin subunit 1 is the largest subunit of the dynactin complex, an activator of the molecular motor protein complex dynein. Reduced levels of DCTN1 mRNA and protein have been found in sporadic amyotrophic lateral sclerosis (ALS) patients, and mutations have been associated with disease, but the role of this protein in disease pathogenesis is still unknown.

METHODS:

We characterized a Dynactin1a depletion model in the zebrafish embryo and combined in vivo molecular analysis of primary motor neuron development with live in vivo axonal transport assays in single cells to investigate ALS-related defects. To probe neuromuscular junction (NMJ) function and organization we performed paired motor neuron-muscle electrophysiological recordings and GCaMP calcium imaging in live, intact larvae, and the synapse structure was investigated by electron microscopy.

RESULTS:

Here we show that Dynactin1a depletion is sufficient to induce defects in the development of spinal cord motor neurons and in the function of the NMJ. We observe synapse instability, impaired growth of primary motor neurons, and higher failure rates of action potentials at the NMJ. In addition, the embryos display locomotion defects consistent with NMJ dysfunction. Rescue of the observed phenotype by overexpression of wild-type human DCTN1-GFP indicates a cell-autonomous mechanism. Synaptic accumulation of DCTN1-GFP, as well as ultrastructural analysis of NMJ synapses exhibiting wider synaptic clefts, support a local role for Dynactin1a in synaptic function. Furthermore, live in vivo analysis of axonal transport and cytoskeleton dynamics in primary motor neurons show that the phenotype reported here is independent of modulation of these processes.

CONCLUSIONS:

Our study reveals a novel role for Dynactin1 in ALS pathogenesis, where it acts cell-autonomously to promote motor neuron synapse stability independently of dynein-mediated axonal transport.

KEYWORDS:

Amyotrophic lateral sclerosis; Axonal transport; Dynactin1; Neuromuscular junction; Zebrafish

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