Zebrafish as an Animal Model for Movement Disorders Alec Rich Tyler Tharp Shabaka Johns

Why Zebra Fish? They are vertebrates and therefore more closely related to humans than other genetic model organisms Short generation time (3 months) Breed prodigiously (Hundreds of offspring per female per week) Embryos develop externally and can be readily manipulated genetically Patterning, pathfinding and connectivity in the CNS of the zebrafish have all been deciphered and correlate with the human CNS Zebrafish mutations phenocopy many human disorders and the genome sequence of zebrafish is near completion

How does it work? Micro-injection of antisense morpholino oligonucleotides into zebrafish embryos at the single cell stage can be used to suppress the translation of a particular gene during early development It allows the selection and subsequent breeding of zebrafish carrying a mutation in a particular gene of interest by genotyping the progeny of N-ethyl-N-nitrosourea mutagenized fish

Disadvantages The main disadvantage of the morpholino technique, is that they lose their efficacy after day 5 of the development

The dopaminergic nervous system in zebrafish DA neurons are first detected between 18 and 19 h post- fertilization in a cluster of cells in the posterior tuberculum of the ventral diencephalon. These neurons represent the DA system ascending to the striatum, comparable with the nigrostriatal system in humans

Past experiments Mutant zebrafish strains have been very useful in improving our understanding of the molecular pathways Zebra Fish have improved our understanding of three major signaling pathways in the development of DA neurons. - Sonic hedgehog - Fibroblast growth factor 8 - Nodal pathways

Zebrafish and Parkinson's Systemic injection of MPTP or 6-hydroxydopamine caused DA and noradrenaline concentrations in brain tissue to significantly decrease without a change of tyrosine hydroxylase or caspase 3 protein levels. The swimming velocity and total distance moved decreased after exposure to both neurotoxins Motor behavior can also be altered by administration of the pesticides rotenone and paraquat in both larval and adult zebrafish

Zebrafish and the quest for disease-modifying therapy Zebrafish have proven to be a great model for rapid molecule screening. Pros: They don’t develop an blood brain barrier until 5dpf Easily farmed and much more cost efficient for early testing of molecules\ Cons: Not a single positive hit from a zf drug screening has even entered phase 1 clinical trial Drugs that have a significant affect on DA neurons in zf may not have the same affect on DA neurons in humans

Future Prospects Zebrafish: relatively new model Cannot be sure yet whether it is going to contribute successful research or not Working on developing genome lines with similar PD and neurodegenerative features to raise and test. Rodents: Been using mice since 1960 Run into multiple failures do to the blood brain barrier No model has shown true success, only shortcomings. There is a desperate need for new aproaches