Loss of GBA in zebrafish leads to dopaminergic neurodegeneration, but overexpression of α-synuclein does not further worsen degeneration

Parkinson's disease is a neurodegenerative disorder that causes motor and nonmotor symptoms due to the loss of dopaminergic nerves and is characterized by the presence of Lewy bodies, which are mainly composed of α-synuclein. Glucosylceramidase beta (GBA), which is a causative gene of autosomal recessive Gaucher disease, is also known to be a risk gene for Parkinson's disease. In this study, we tried to detect synergistic effects of α-synuclein accumulation and gba depletion on dopaminergic neurodegeneration in zebrafish.We generated a transgenic line of zebrafish overexpressing the A53T α-synuclein and gba mutant fish, and analyzed pathologies of α-synuclein aggregation and neurodegeneration.Zebrafish overexpressing the A53T α-synuclein did not exhibit α-synuclein aggregate formation. After the loss of gba function in this mutant α-synuclein transgenic line, we observed the marked presence of α-synuclein aggregates. Loss of gba function in zebrafish resulted in dopaminergic and noradrenergic neurodegeneration but this level of neurodegeneration was not exacerbated by overexpression of mutant α-synuclein.These results indicate that loss of gba function was sufficient to generate a neurodegenerative phenotype in zebrafish regardless of the expression of α-synuclein.