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

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.

Novel pre-clinical model for CDKL5 Deficiency Disorder

“…At this age, cdkl5 -/mutant zebrafish displayed reduced swimming however, we did not detect any defects in muscle formation or patterning during early muscle development. Defects in motor neuron axon length and branching have been shown, in zebrafish models of Motor Neuron Disease, to correlate with shorter swimming distances [24]. This supports the idea that the defects in swimming performance of cdkl5 -/mutant zebrafish may be caused by impaired motor neuron outputs.…”

Genetic compensation in a stable slc25a46 mutant zebrafish: A case for using F0 CRISPR mutagenesis to study phenotypes caused by inherited disease

“…Images from three separate experiments were blindly evaluated for qualitative inclusion into either "normal" group or "disrupted" group. The normal group was assigned to images with stereotypical motor axons shaped into normal hooks as on the images of uninjected controls [60]. The affected group was assigned to images with any number of disrupted motoneuron axons, such as axonal projections crossing into a nearby segment, truncated axons with projections not reaching back up to form the hook shape or aberrant hooks missing stereotypical branching pattern [60,61].…”

Automated in vivo drug screen in zebrafish identifies synapse-stabilising drugs with relevance to spinal muscular atrophy

“…Moreover, by extending the capacity of automatic imaging to earlier developmental stages (28-30 hpf), the VAST system could be used in future studies that have primary motor axon growth as read-out. A wide range of zebrafish models could be suitable for our automated system, such as the established gene-disruption models of C9orf72, TDP43 and SOD1 ( Lissouba et al, 2018 ; Robinson et al, 2019 ) for ALS, and the neurexin mutants for SMA ( Koh et al, 2020 ). Furthermore, motor axon aberrations in neuroserpin mutants could be used to screen for neurodegenerative disorders ( Han et al, 2021 ).…”