Parkin deficiency delays the appearance of motor dysfunction in hA30Pα -syn mice in a dose-dependent manner. Motor functions were assessed with the extension reflex (A, B), the rotarod (C) and footprint (D) tests. For each test and for each genotype, the mean performance scores are presented as a function of age (n = 11–14 per genotype); the curves correspond to the weight-adjusted models used for the statistical comparisons. (E) The penetrance of the phenotype was calculated as the age at which the animals were unable to perform the rotarod test (Kaplan-Meier analysis). *; **: different from hA30Pα-syn+/+ mice with p < 0.01; p < 0.0001; #; ##: different from parkin-/-; hA30Pα-syn+/+ mice, with p < 0.05; p < 0.0001.