It has been known for a while that alpha-synuclein is important in Parkinson's disease, and here is insight into how the condition might spread within the brain once it gets started: "damaged alpha-synuclein proteins [can] spread in a 'prion-like' manner, an infection model previously described for diseases such as BSE (mad cow disease). ... This is a significant step forward in our understanding of the potential role of cell-to-cell transfer of alpha-synuclein in Parkinson's disease pathogenesis and we are very excited about the findings ... A previous observation that aggregated alpha-synuclein protein gradually appears in healthy young neurons transplanted to the brains of Parkinson's patients initially gave rise to the group's hypothesis of cell-to-cell protein transfer. The theory has now been tested in several cell culture experiments. ... We have now shown that alpha-synuclein not only can transfer from one cell to another, but also that the transferred protein can seed aggregation of alpha-synuclein in recipient cells as well. This could be an important mechanism for the spread of the pathology. ,... Transplant trials in mice [strengthened] the theory of cell-to-cell transfer ... Six months after Parkinson's disease model mice were transplanted with healthy dopamine neurons, we found that the new brain cells contained human alpha-synuclein, indicating cell-to-cell transfer from the host brain to the transplants."