Various PD-associated abnormalities, including neurite outgrowth abnormalities, DA neuron death induced by the addition of 6-hydroxydopamine, tau and α-synuclein deposition, and gene expression changes in DA neurons, have been observed in DA neurons derived from iPS cells prepared from a patient with a LRRK2 gene mutation (G2019S mutation) and in isogenic control iPS cells in which the G2019S mutation was introduced. The gene discussed is SNCA; the disease is Parkinson disease.