Background: Parkinson’s disease (PD) is the most common neurodegenerative motor disorder, which is currently incurable. Mutations in many genes have been demonstrated to be the primary risk factors associated with the familial or idiopathic PD; however, the mechanisms underlying these genetic mutations resulting in parkinsonism remains unclear. Phospholipase A2 group VI (PLA2G6) has been shown to regulate lipid metabolism and homeostasis in the nervous system. Previous studies have shown that point mutations in PLA2G6 might be the risk factors associated with the young–onset of dystonia–parkinsonism type 14 (PARK14). However, limited information is available regarding its pathogenic role and the mechanism underlying its function.
Methods: To study the role of PLA2G6 mutations in zebrafish PARK14 models, we injected different mutation constructs of human PLA2G6 genes and zebrafish pla2g6 deletion constructs in the zebrafish larvae. We analyzed the locomotion behavior, performed immunohistochemistry to examine the formation of dopaminergic neurons, and identified the defective metabolites affected by PLA2G6 mutations through metabolomics analysis.
Results: Injection of human PLA2G6 mutations and zebrafish pla2g6 deletion constructs induced symptoms such as motility defects and reduced number of dopaminergic neurons, and these symptoms resembled those observed in PARK14. These phenotypes could be rescued by treatment with L-dopa. Furthermore, the injection of two PLA2G6 mutation constructs, D331Y and T572I, led to a decrease in the phospholipase activity of PLA2G6 and its lipid metabolites, indicating that these two mutations are the loss-of-function mutations. We further performed metabolomics analysis to identify which lipids are majorly affected by the overexpression of PLA2G6 and PLA2G6 mutants. We found that injecting D331Y or T572I mutation constructs led to higher phospholipid and lower DHA levels.
Conclusions: D331Y and T572I injections in zebrafish were sufficient to create a PD phenotypes. In addition, D331Y and T572I are loss of function mutations and cause defective phospholipase activity and reduced the level of DHA. These results have helped us elucidate the role of PLA2G6 mutations in PARK14 and further led to a deeper understanding of the molecular mechanisms underlying PD. The results of this study may also facilitate the development of therapeutic strategies for PD.