1. Haematology Department, University College London, London, United Kingdom;
2. Institute of Pharmaceutical Science, King’s College London, London, United Kingdom;
3. MRC Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, University of Oxford, Oxford, United Kingdom;
4. Paediatrics Department, Boston Children's Hospital, Boston, MA; and
5. Haematology Department, Hammersmith Hospital, Imperial College London, London, United Kingdom