PET and SPECT analysis of nigrostriatal dopamine neuron terminal markers in PD patients showed a progressive loss of DAT and vesicular monoamine transporter 2 (VMAT2) and diminished 3,4-Dihydroxyphenylacetic acid (DOPAC) activity using [18F]-fluorodopa PET, as well as normal or increased levels of D2 receptor in the striatum [95,119,122,123]. The gene discussed is SLC6A3; the disease is Parkinson disease.