The authors wish to thank Marianne Juhlin and AnnaKarin Oldén for their excellent technical support. We thank Andrew C. McCourt for the linguistic revision of this manuscript. This work was funded by grants from the Swedish Research Council; Torsten Söderberg Foundation and Swedish Parkinson Foundation (J.-Y. L.). S.H., O.C., T.A., L.R. and J.-Y. L are active and supported by BAGADILICO—Excellence in Parkinson and Huntington Research, and the Strategic Research Area Multipark (Multidisciplinary research in Parkinson’s disease at Lund University); L.B. and R.M. are supported by the Centre National de la Recherche Scientifique and Grants from the Agence Nationale de la Recherche (ANR-11-BSV8-021-01) and a ‘Coup d’Elan a la Recherche Francaise’ award from Fondation Bettencourt Schueller. Z.Y.W. and J.-Y.L. are supported by National Natural Science Foundation of China (81430025) and the Fundamental Research Funds for Central Universities of China (N130120002).

Conflict of interest

The authors declare no competing financial interests.