In addition, the transgene is constitutively expressed in most rodent models, including our rats, so they were able to develop compensatory mechanisms which potentially counteracted the toxic effects of mutated LRRK2. While LRRK2 mutations in familiar PD are constitutively expressed as well, the over-expression of mutated LRRK2 might trigger the compensatory effects. The gene discussed is LRRK2; the disease is Parkinson disease.