Transgenic mice expressing S129 phosphorylation mutations in α-synuclein

• We developed transgenic mice expressing only S129D or S129A human α-synuclein.
• Transgene expression and localization were normal and at endogenous levels.
• No gross abnormalities in behavior or motor defects indicating toxicity were seen.
• Mice had normal gut motility and no neurodegeneration or aggregation in the brain.
• Presynaptic vesicle localization was normal in phosphomutant mice.

Aggregated α-synuclein is a predominant constituent of Lewy bodies, the intracellular protein aggregates seen in Parkinson's disease. While most α-synuclein in the nervous system is unphosphorylated, the majority of α-synuclein in Lewy bodies is phosphorylated at serine 129 (S129). We developed transgenic mice expressing human SNCA with either a phosphomimic (S129D) or a non-phosphorylatable (S129A) mutation, on a mouse Snca knockout background. Transgenic lines with each mutation expressing the human α-synuclein protein at levels ranging from 0.3 to 1.9 fold of endogenous mouse protein were chosen to avoid toxic overexpression effects. We previously demonstrated an altered distribution of presynaptic vesicles in Snca knockout mice, as well as enhanced interaction between presynaptic cytoskeletal proteins and α-synuclein when phosphorylated at S129 or carrying an S129D mutation. We therefore examined α-synuclein's synaptic localization and the distribution of presynaptic vesicles in these mutants. In addition, we evaluated the transgenic lines for reduced colonic motility, an early marker of α-synuclein pathology, and α-synuclein aggregates. No abnormalities were detected in mice expressing either phosphorylation mutant protein as their only α-synuclein protein. These results suggest the S129A and S129D mutations have no obvious effect on α-synuclein function.