SLC6A3 and Parkinsonism: We therefore investigated whether the Mn-induced parkinsonism-like phenotype observed in Mn-exposed mutant embryos is due to a defect in dopaminergic signaling by measuring the expression of the dopamine transporter (dat) and tyrosine hydroxylase (th) in embryos with and without Mn exposure; both dat and th mRNA are commonly measured as molecular markers of dopaminergic neurons in zebrafish [39,40].