[1] Hosp Sick Children, Toronto, ON M5G 1X8, Canada
[2] UCL, London WC1E 6BT, England
[3] Univ Penn, Philadelphia, PA 19104 USA
[4] Harvard Univ, Sch Med, Boston, MA USA
[5] Queens Univ, Kingston, ON K7L 3N6, Canada
[6] Ctr Thalassemia, Athens, Greece