Interestingly, HO-1−/− mice have been shown to be similarly sensitive to MPTP as wild-type littermates [146], although the previous studies showed ample evidence for neuroprotective activities of HO-1, e.g., adenoviral overexpression of HO-1 increased significantly the survival rate of dopaminergic neurons in the rat model of PD [148]. The gene discussed is HMOX1; the disease is Parkinson disease.