1. Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT 06536-0812.
2. Clinical Genetics Center, University Hospital, Nijmegen, Netherlands.
3. INSERM Unité 192, Hôpital Necker-Enfants Malades, Paris, France.
4. Department of Pathology, University of Helsinki, Helsinki, Finland.
5. Department of Human Genetics, University Hospital, Ghent, Belgium.
6. Biocenter and Department of Biochemistry, University of Oulu, Oulu, Finland.