While Cordero-Llana and others (109) suggested a synergistic neurorestorative effect of virally delivered CDNF and MANF on nigral dopamine neurons in a 6-OHDA model of PD, simultaneous deletion of endogenous CDNF and MANF did not result in loss of nigral dopamine neurons in aged mice (52). Here, MANF is linked to Parkinson disease.