1. Center for Human and Clinical Genetics, 2 Department of Medical Statistics and Bioinformatics, Leiden University Medical Center, 2300 RC Leiden, The Netherlands, 3 School of Biological Sciences, Royal Holloway – University of London, Egham, Surrey, TW20 0EX, UK and 4 Thérapie des Maladies du Muscle Strié, Institut de Myologie, UM76, Université Pierre et Marie Curie, INSERM-U974, CNRS-UMR7215, Paris, France