MAPT and multiple system atrophy: It is possible that unknown factors, such as post-translational modifications of α-synuclein and/or non-proteinaceous cofactors, are required for formation of the JOS, Lewy and MSA folds. Similar to what has been done for tau [21], it will be important to develop conditions that permit the assembly of recombinant α-synuclein into filaments with identical structures to those from human brains.