[1] Whitehead Inst Biomed Res, Cambridge, MA 02142 USA
[2] Childrens Hosp Boston, Div Hematol Oncol, Boston, MA USA
[3] Singapore Massachusetts Inst Technol, Singapore, Singapore
[4] ASTAR, Genome Inst Singapore, Singapore, Singapore
[5] Lund Univ, Dept Mol Med & Gene Therapy, Lund, Sweden
[6] MIT, Dept Biol, Cambridge, MA USA
[7] MIT, Dept Biol Engn, Cambridge, MA 02139 USA