Presynaptic imaging of the dopamine transporter (DAT) using [123I]N-w-fluoropropyl-2β-carbomethoxy-3β-(4-iodophenyl)nortropane (123I-FP-CIT) SPECT [10] differentiates individuals with PD from normal controls quite reliably and is commonly used for diagnostic purposes. The gene discussed is SLC6A3; the disease is Parkinson disease.