1. Departments of Pediatrics, Obstetrics & Gynecology, and Laboratory Medicine, National University of Singapore and National University Hospital, Singapore 119074, Singapore
2. Johns Hopkins Singapore Pte. Ltd., Singapore 117610, Singapore
3. Department of Pediatrics and McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21287
4. MRC Molecular Haematology Unit, Institute of Molecular Medicine, Oxford OX3 9DU, United Kingdom