1. Department of Human Genetics; Leiden University Medical Center; Leiden The Netherlands
2. Neuromuscular Disease Unit; Department of Neurology; University of Rochester Medical Center; Rochester New York
3. Department of Neurology; University of Texas Southwestern Medical Center; Dallas Texas
4. Department of Clinical Genetics; Leiden University Medical Center; Leiden The Netherlands
5. University of Texas Health Science Center at San Antonio; Chromosome 18 Research Center; San Antonio Texas
6. Division of Human Biology; Fred Hutchinson Cancer Research Center; Seattle Washington