MED12 and acute lymphoblastic leukemia: We also identified two novel candidate driver genes on the X chromosome: a novel nonsense mutation in the deubiquitinating protease USP9X (p.Q117*) in male patient 194; and 3 novel mutations in MED12, a member of the Mediator complex involved in regulating RNA polymerase II-dependent transcription, were found in male patient 744 (splice site mutation g.chrX:70339329T>C) and female ETP-ALL patients 791 (missense mutation p.R1989H) and 879 (frameshift insertion p.V167fs).