1. Columbia University, Department of Neurology, New York, NY U.S.A.
2. University Medical Center Groningen, University of Groningen, Department of Cell Biology, Groningen, The Netherlands
3. Current address: Erasmus MC – Sophia Children's Hospital, Department of Pediatric Surgery, Rotterdam, The Netherlands
4. Columbia University, Department of Pathology and Cell Biology, New York, NY U.S.A.