Adeno-associated virus serotype 2 (AAV-2) vector encoding the human NRTN gene (CERE120) was designed to deliver the NRTN gene to the putamen (± the substantia nigra) to protect or restore degenerating nigrostriatal dopaminergic neurons and to potentially provide clinical benefits in Parkinson’s disease (Kordower et al., 2006; Gasmi et al., 2007). Here, NRTN is linked to Parkinson disease.