Analyses of the candidate mutations in BaF3 cells. (A) JAK2M535I does not induce the growth of BaF3 cells in the absence of IL-3. (B) JAK3A573V induces IL-3–independent growth of BaF3 cells. The growth of JAK3V722I cells is observed at later time points. (C) Expression of MPLT487A results in IL-3–independent growth of BaF3 cells. MPLT487A induces IL-3–independent growth of BaF3 cells slightly later than MPLW515L does; MPLT487V is not able to induce growth in these conditions. Two independent experiments, each in triplicate, were performed, and the mean plus or minus SD of 1 representative experiment is shown.