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Updated: May 13, 2025
Locomotor Assessment of 6-Hydroxydopamine-induced Adult Zebrafish-based Parkinson's Disease Model
Published on: December 28, 2021
A zebrafish model of acmsd deficiency does not support a prominent role for ACMSD in Parkinson's disease
Emma Fargher1,2, Marcus Keatinge1,2,3, Oluwaseyi Pearce1,2
1Sheffield Institute for Translational Neuroscience (SITraN), University of Sheffield, Sheffield, UK.
Abstract:
Single nucleotide polymorphisms adjacent to the α-amino-β-carboxymuconate-ε-semialdehyde decarboxylase (ACMSD) gene have been associated with Parkinson's disease (PD) in genome-wide association studies (GWAS). However, its biological validation as a PD risk gene has been hampered by the lack of available models. Using CRISPR/Cas9, we generated a zebrafish model of acmsd deficiency with marked increase in quinolinic acid. Despite this, acmsd-/- zebrafish were viable, fertile, morphologically normal and demonstrated no abnormalities in spontaneous movement. In contrast to the postulated pro-immune pathomechanism linking ACMSD to PD, microglial cells and expression of the proinflammatory cytokines cxcl8, il-1β, and mmp9 were similar between acmsd-/- and controls. The number of ascending dopaminergic neurons, and their susceptibility to MPP+, was also indistinguishable. An upregulation of kynurenine aminotransferase activity was identified in acmsd-/- zebrafish which may explain the absence of neurodegenerative phenotypes. Our study highlights the importance of biological validation for putative GWAS hits in suitable model systems.
Insights
Genetic variations near the ACMSD gene are linked to Parkinson's disease (PD). However, a new zebrafish model shows ACMSD deficiency does not cause PD-like neurodegeneration, suggesting other factors are involved.
Area of Science:
- Neuroscience
- Genetics
- Biochemistry
Background:
- Genome-wide association studies (GWAS) identified single nucleotide polymorphisms near the alpha-amino-beta-carboxymuconate-epsilon-semialdehyde decarboxylase (ACMSD) gene associated with Parkinson's disease (PD).
- Biological validation of ACMSD as a PD risk gene is limited due to a lack of suitable model systems.
Purpose of the Study:
- To generate and characterize a zebrafish model of ACMSD deficiency to investigate its role in Parkinson's disease pathogenesis.
- To assess neuroinflammation, dopaminergic neuron integrity, and susceptibility to neurotoxins in acmsd-deficient zebrafish.
Main Methods:
- CRISPR/Cas9 gene editing was used to create acmsd knockout zebrafish (acmsd-/-).
- Phenotypic analysis included assessment of viability, morphology, spontaneous movement, microglial cell counts, pro-inflammatory cytokine expression (cxcl8, il-1β, mmp9), dopaminergic neuron counts, and MPP+ susceptibility.
- Biochemical assays were performed to measure kynurenine aminotransferase activity.
Main Results:
- acmsd-/- zebrafish were viable and morphologically normal with no movement abnormalities.
- No significant differences were observed in microglial cell populations or pro-inflammatory cytokine expression between acmsd-/- and control zebrafish.
- Dopaminergic neuron numbers and susceptibility to MPP+ neurotoxin were indistinguishable between groups.
- Upregulated kynurenine aminotransferase activity was detected in acmsd-/- zebrafish.
Conclusions:
- ACMSD deficiency in zebrafish does not recapitulate key pathological features of Parkinson's disease, challenging the postulated pro-immune pathway.
- Upregulated kynurenine aminotransferase activity may compensate for ACMSD loss, preventing neurodegenerative phenotypes.
- This study underscores the necessity of biological validation in appropriate model systems for genetic associations identified through GWAS.
