Linkage analysis in mouse PD models have identified several QTLs linked to midbrain neurodegeneration [23,33,34]: we recently performed linkage analysis in an F2 intercross between C57Bl/6N and Swiss-OF1-En1+/− mice, identifying multiple QTLs linked to susceptibility of mice to midbrain neurodegeneration and striatal fiber dysfunction [23]. Here, EN1 is linked to Parkinson disease.