(d) Ba/F3 cells expressing either FOXO3(A3)-ER or FOXO4(A3)-ER were stimulated with 4-OHT in the presence of mIL-3. Relative mRNA levels of glutamine synthetase were analysed using quantitative rtPCR. Data are represented as mean ±  s.e.m. values normalized for B2M (n=3). **P0.01. 