To investigate the effect of an accumulation of wild-type α-synuclein, we studied a transgenic mouse model of PD expressing human wild-type α-synuclein under the control of the mouse α-synuclein promoter, which is likely to lead to an expression pattern of the human α-synuclein that is similar to the pattern of endogenous mouse α-synuclein expression. The gene discussed is SNCA; the disease is Parkinson disease.