EphB4 deficiency affects mesoderm gene expression during EB differentiation. RT-PCR of EBs at different time points. ES cells from EphB4^+/–1 and EphB4^–/–1 were induced for differentiation. RNA samples were harvested at day 1, 3, 4, 5, 7, and 9 of differentiated EBs and analyzed by RT-PCR. Size of each RT-PCR product is shown in Table 1. None of the samples showed genomic DNA amplification (not shown).