A motor endurance assay for zebrafish larvae: proof of principle in chemical and genetic models of neurological disease

Motor fatigability is an early feature of neurological disease, including amyotrophic lateral sclerosis (ALS), but motor endurance assays for zebrafish are largely restricted to juvenile or adult animals. Here, we developed a gravity-fed counter-current swimming assay to quantify motor endurance in 5-7 days post-fertilisation (dpf) zebrafish larvae, which supports the parallel testing of multiple larvae. We detected an increase in motor endurance induced by exposure to caffeine, and a reduction induced by the dopaminergic toxin 1-methyl-4-phenylpyridinium (MPP+). In these tests, motor endurance showed a greater dynamic range than spontaneous locomotion. Further, we generated and tested transgenic zebrafish larvae with neuron-restricted overexpression of human TDP43 (hTDP43), the major pathological protein in ALS patients. Zebrafish with neuronal hTDP43 expression showed ALS-relevant hTDP43 mislocalisation and significantly reduced motor endurance at 5 dpf. This method for motor endurance assessment in 5-7 dpf zebrafish is simple, sensitive, and enables the characterisation of motor fatigability in models of human neurological disease (TDP43-linked ALS and MPP+-induced parkinsonism).