Conservation of Parkinson’s disease–associated genes inC. elegans. Genes associated with PD are listed in the oval along with orthologs (italics) in C. elegans. (As indicated by the question mark, α-synuclein represents the only PD-associated gene that does not have a strong ortholog.) A dopamine neuron schematizes known and predicted genes involved in dopamine biosynthesis and metabolism Red circles represent dopamine; blue cylinders represent dopamine transporter; heptahelical structures represent pre- and postsynaptic dopamine receptors. Protein locations are putative. AAAD, aromatic L-amino acid decarboxylase; MAO, monoamine oxidase; TH, tyrosine hydroxylase; VMAT [the activity of which is indicated by appearance of black circles (membranes of dopamine-containing synaptic vesicles)], vesicular monoamine transporter.