1. Department of Physiology (P.R., H.L., L.S., P.P., M.P.) University of Helsinki, FIN-00290 Helsinki, Finland
2. Turku Center for Disease Modeling (P.R., L.S., P.P., M.P.) University of Helsinki, FIN-00290 Helsinki, Finland
3. Institute of Biomedicine, Department of Biochemistry and Food Chemistry (M.K., J.-P.S.) University of Helsinki, FIN-00290 Helsinki, Finland
4. Laboratory of Electron Microscopy (L.S.), University of Turku, FIN-20520 Turku, Finland;
5. Department of Medical Biochemistry and Developmental Biology (K.S.), Institute of Biomedicine, University of Helsinki, FIN-00290 Helsinki, Finland