In vivo and in vitro studies have also reported that the direct infusion of CDNF proteins or CDNF-engineered vectors significantly protect and reverse the loss of DAergic neurons in PD models (Lindholm et al., 2007[17]; Mei and Niu, 2015[22]; Ren et al., 2013[32]). The gene discussed is CDNF; the disease is Parkinson disease.