1. MRC Protein Phosphorylation and Ubiquitylation Unit, College of Life Sciences, University of Dundee, Dow Street, Dundee DD1 5EH, Scotland, U.K.
2. Department of Neurosurgery, Massachusetts General Hospital, and Harvard Medical School, Boston, MA 02114, U.S.A.
3. Manton Center for Orphan Disease Research, Children's Hospital Boston, Boston, MA 02115, U.S.A.