Stable transgenic C9orf72 zebrafish model key aspects of the ALS/FTD phenotype and reveal novel pathological features

Abstract

A hexanucleotide repeat expansion (HRE) within the chromosome 9 open reading frame 72 (C9orf72) gene is the most prevalent cause of amyotrophic lateral sclerosis/fronto-temporal dementia (ALS/FTD). Current evidence suggests HREs induce neurodegeneration through accumulation of RNA foci and/or dipeptide repeat proteins (DPR). C9orf72 patients are known to have transactive response DNA binding protein 43 kDa (TDP-43) proteinopathy, but whether there is further cross over between C9orf72 pathology and the pathology of other ALS sub-types has yet to be revealed.To address this, we generated and characterised two zebrafish lines expressing C9orf72 HREs. We also characterised pathology in human C9orf72-ALS cases. In addition, we utilised a reporter construct that expresses DsRed under the control of a heat shock promoter, to screen for potential therapeutic compounds.Both zebrafish lines showed accumulation of RNA foci and DPR. Our C9-ALS/FTD zebrafish model is the first to recapitulate the motor deficits, cognitive impairment, muscle atrophy, motor neuron loss and mortality in early adulthood observed in human C9orf72-ALS/FTD. Furthermore, we identified that in zebrafish, human cell lines and human post-mortem tissue, C9orf72 expansions activate the heat shock response (HSR). Additionally, HSR activation correlated with disease progression in our C9-ALS/FTD zebrafish model. Lastly, we identified that the compound ivermectin, as well as riluzole, reduced HSR activation in both C9-ALS/FTD and SOD1 zebrafish models.Thus, our C9-ALS/FTD zebrafish model is a stable transgenic model which recapitulates key features of human C9orf72-ALS/FTD, and represents a powerful drug-discovery tool.Electronic supplementary materialThe online version of this article (10.1186/s40478-018-0629-7) contains supplementary material, which is available to authorized users.

Reduced C9orf72 function leads to defective synaptic vesicle release and neuromuscular dysfunction in zebrafish

“…The model presented here, importantly, display TDP-43 pathology and replicates haploinsu ciency as a major contributor to C9orf72 ALS rather than a full ablation of C9or72 loss-offunction model. Intriguingly, the motor phenotypes observed in C9-miR zebra sh are consistent with several other zebra sh ALS models, including zebra sh model expressing C9orf72-related repeat expansions or DPR 28,42,43 . However, the presence a reduced level of C9orf72 mRNA or protein in these models, as in ALS/FTD, was not examined in these studies.…”

Knock in of a hexanucleotide repeat expansion in the C9orf72 gene induces ALS in rats

“…It is thought that these RNAs may sequester RNA-binding proteins in RNA foci, which, when translated, result in accumulation of unnatural dipeptide repeat (DPR) proteins in the brain. [5][6][7][8][9] A number of transgenic animal models have been employed in studies, including drosophila, 10 zebra fish [11][12][13] and mice. [14][15][16][17] In the transgenic drosophila and zebra fish models, a gain-of-function of C9orf72 repeat expansion caused an accumulation of DPR proteins, or a combination of RNA foci and DPR proteins that was sufficient to promote neurodegeneration, motor neuron loss and muscle atrophy.…”

“…[14][15][16][17] In the transgenic drosophila and zebra fish models, a gain-of-function of C9orf72 repeat expansion caused an accumulation of DPR proteins, or a combination of RNA foci and DPR proteins that was sufficient to promote neurodegeneration, motor neuron loss and muscle atrophy. [10][11][12] However, the data from four reports on BAC transgenic mouse models were equivocal. RNA foci and repeat-associated non-ATG (RAN) proteins were found in all of them, but in two of the studies the mice did not develop the neurodegenerative or behavioral features of ALS/ FTD.…”

Simultaneous analysis of neuroactive compounds in zebrafish

“…25 Genetic and compound-induced disease models in zebrafish larvae have shown promising consistency with rodent models, even for complex diseases like ALS. 29,42 Zebrafish are also well-suited for phenotypic profiling, a quantitative, high-throughput approach to phenotype-first compound discovery. 34,39 Phenotypic profiles are quantitative readouts of the aggregate movement of many larvae on multiwell plates.…”