Loss of parla Function Results in Inactivity, Olfactory Impairment, and Dopamine Neuron Loss in Zebrafish

Abstract

The presenilin-associated rhomboid-like (PARL) gene was found to contribute to mitochondrial morphology and function and was linked to familial Parkinson’s disease (PD). The PARL gene product is a mitochondrial intramembrane cleaving protease that acts on a number of mitochondrial proteins involved in mitochondrial morphology, apoptosis, and mitophagy. To date, functional and genetic studies of PARL have been mainly performed in mammals. However, little is known about PARL function and its role in dopaminergic (DA) neuron development in vertebrates. The zebrafish genome comprises two PARL paralogs: parla and parlb. Here, we established a loss-of-function mutation in parla via CRISPR/Cas9-mediated mutagenesis. We examined DA neuron numbers in the adult brain and expression of genes associated with DA neuron function in larvae and adults. We show that loss of parla function results in loss of DA neurons, mainly in the olfactory bulb. Changes in the levels of tyrosine hydroxylase transcripts supported this neuronal loss. Expression of fis1, a gene involved in mitochondrial fission, was increased in parla mutants. Finally, we showed that loss of parla function translates into impaired olfaction and altered locomotion parameters. These results suggest a role for parla in the development and/or maintenance of DA neuron function in zebrafish.

Cerebroventricular Microinjections of MPTP on Adult Zebrafish Induces Dopaminergic Neuronal Death, Mitochondrial Fragmentation, and Sensorimotor Impairments

“…MPP+ then exerts its effects on cells expressing th1 and dat, as shown through decreases in respective gene mRNA levels. The >50% dat expression remaining can be explained by the remaining dopaminergic neurons expressing dat as a means to recycle synaptic dopamine into the cytosol of dopaminergic neurons (Shimizu and Prasad, 1991;Giros et al, 1992;Sulzer et al, 2016;Merhi et al, 2021). Although we cannot rule out the possibility of a transient downregulation in dat/th1 expression that may contribute to the functional impairment and recovery of zebrafish behavior, the effect of MPTP on tom20 expressing dopaminergic neurons combined with the eGFP data are suggestive of neurodegeneration occurring.…”

Comparison of the effect of rotenone and 1‑methyl‑4‑phenyl‑1,2,3,6‑tetrahydropyridine on inducing chronic Parkinson's disease in mouse models

“…Genetic susceptibility and environmental exposures increase the risk of developing PD ( 7 , 8 ). As the majority of PD cases are sporadic, environmental factors may be also important ( 9 ). At present, there is no definitive cure, and the clinical diagnosis of PD is still based on the characteristic symptoms of motor dysfunction ( 10 ).…”

Regulation of heart rate following genetic deletion of the ß1 adrenergic receptor in larval zebrafish

“…A schematic step‐by‐step overview of the protocol used to generate the adrb1 −/− line is provided in Figure S1. Microinjections were performed in 1‐cell stage embryos as described previously 56 . The injection solution comprised of the following: 40 ng/μl for each sgRNA, 20 ng/μl Cas9 protein (New England BioLabs, Ipswich, MA, USA), and 0.1% Phenol Red (Sigma, Burlington, MA, USA).…”