PINK1 and Parkinson disease: Because α-synuclein immunoreactive protein aggregates are pathognomonic for PD, and because genetic, biochemical in vitro and in vivo studies suggest α-synuclein oligomerization or aggregation is linked to the underlying mechanisms of neurodegeneration in PD, we focused our analysis of PINK1-/- rats on characterizing the pattern and age-dependence of α-synuclein immunoreactivity throughout the brain.