Motor Neuron Abnormalities Correlate with Impaired Movement in Zebrafish that Express Mutant Superoxide Dismutase 1.

Katherine J Robinson,Claire G Winnick,Angela S Laird,Garth A Nicholson,Kristy C Yuan,Julie D Atkin,Hamideh Shahheydari,Madelaine C Tym,Alison L Hogan,Emily K Don,Maxinne Watchon,Nicholas J Cole,Caitlin W Lucas,Ian P Blair

doi:10.1089/zeb.2018.1588

Katherine J Robinson, Claire G Winnick + Show 12 more

Open Access

https://doi.org/10.1089/zeb.2018.1588

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Abstract

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by progressive loss of motor neurons. ALS can be modeled in zebrafish (Danio rerio) through the expression of human ALS-causing genes, such as superoxide dismutase 1 (SOD1). Overexpression of mutated human SOD1 protein causes aberrant branching and shortening of spinal motor axons. Despite this, the functional relevance of this axon morphology remains elusive. Our aim was to determine whether this motor axonopathy is correlated with impaired movement in mutant (MT) SOD1-expressing zebrafish. Transgenic zebrafish embryos that express blue fluorescent protein (mTagBFP) in motor neurons were injected with either wild-type (WT) or MT (A4V) human SOD1 messenger ribonucleic acid (mRNA). At 48 hours post-fertilization, larvae movement (distance traveled during behavioral testing) was examined, followed by quantification of motor axon length. Larvae injected with MT SOD1 mRNA had significantly shorter and more aberrantly branched motor axons (p < 0.002) and traveled a significantly shorter distance during behavioral testing (p < 0.001) when compared with WT SOD1 and noninjected larvae. Furthermore, there was a positive correlation between distance traveled and motor axon length (R2 = 0.357, p < 0.001). These data represent the first correlative investigation of motor axonopathies and impaired movement in SOD1-expressing zebrafish, confirming functional relevance and validating movement as a disease phenotype for the testing of disease treatments for ALS.

Highlights

Amyotrophic lateral sclerosis (ALS), known as motor neuron disease, is a fatal neurodegenerative disease characterized by progressive loss of motor neurons.[1]
Tukey post-hoc analysis revealed that larvae injected with MT superoxide dismutase 1 (SOD1) had significantly shorter axons than larvae injected with WT SOD1 (151.53 – 5.00 vs. 173.64 – 4.56; n = 37–44; p = 0.004) and noninjected larvae (188.34 – 4.78; n = 44; p < 0.001) (Fig. 1C)
Larvae injected with MT SOD1 had significantly more axons with aberrant branching than larvae injected with WT SOD1 (1.432 – 0.179 vs. 0.409 – 0.164; p < 0.001) or noninjected larvae (0.100 – 0.172, p < 0.001) (Fig. 1D)

Summary

Introduction

Amyotrophic lateral sclerosis (ALS), known as motor neuron disease, is a fatal neurodegenerative disease characterized by progressive loss of motor neurons.[1] Patients with ALS develop muscle atrophy and paralysis, originating in either the limbs or bulbar regions, and usually die within 3–5 years of diagnosis.[2] While most cases of ALS are considered sporadic, around 10% of ALS is inherited, known as familial ALS (FALS).[1] Several ALS-causing gene mutations have been identified, including mutations in the superoxide dismutase 1 (SOD1) gene (20% of FALS3), TDP43 gene (

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