Localization of phosphorylated α-synuclein in a subset of presynaptic terminals in A53T-BAC-SNCA mice. A–D, TEM images of pre-embedding immunogold-labeled samples from A53T-BAC-SNCA mice at 1 (A), 3 (B), 6 (C), and 22 (D) months. Note that the immunogold particles, indicating phosphorylated α-synuclein, were predominantly localized to presynaptic terminals. Immunogold particles were often seen in clusters. E, A low-magnification image from an A53T-BAC-SNCA mouse at 3 months of age demonstrates that a subset of large presynaptic terminals was immunopositive for phosphorylated α-synuclein. s: spine; T: presynaptic terminals with immunoreactivity for phosphorylated α-synuclein; t: presynaptic terminals lacking immunoreactivity for phosphorylated α-synuclein. Scale bars: 500 nm.