In addition to α-synuclein concentration, our data highlight relationships between the distribution of α-synuclein among PBS-, TrX- and SDS tissue fractions and synucleinopathy load following PFF inoculation, with higher baseline levels of TrX-soluble α-synuclein predisposing select brain regions to developing more severe synucleinopathy in PFF mice. This evidence concerns the gene SNCA and synucleinopathy.