The locomotor dysfunction was also shown to be a result of DA neuron degeneration driven by mutations in some PD-related genes such as parkin and LRRK2. Previous studies on the Drosophila PD model showed that a mutation in parkin or the overexpression of parkin mutant gene caused the degeneration of DA neurons, specifically in the PPL1 cluster20,26. The gene discussed is LRRK2; the disease is Parkinson disease.