Immature sca-1⁺/c-kit⁺/Gr-1^- hematopoietic cells from Tpo^-/- mice display reduced VEGF-A–specific mRNA levels. Whole bone marrow cells were prepared from control C57BL/6 and Tpo^-/-mice. The cells were pooled (experiment 1: n = 4 C57BL/6, n = 4 Tpo^-/- mice; experiment 2: n = 4 C57BL/6, n = 5 Tpo^-/-mice) and Sca-1⁺/c-kit⁺/Gr-1^- cells were collected. Immediately after the collection, mRNA was prepared for real-time PCR analysis. Each column represents an average of VEGF-A mRNA levels normalized to a GAPDH internal control ± SD of 2 experiments (▪, C57BL/6; ▨, Tpo^-/-).