Figure 1

ERG expression in differentiating EBs is endothelial-cell specific. (A) Quantitative RT-PCR of RNA derived from EBs at different stages of differentiation (days 0-10), showing temporal correlation in the expression of ERG (blue) and endothelial-specific VE-cadherin (purple). Copy numbers (normalized per 10,000 copies GAPDH) are shown for VE-cadherin (left) and ERG (right) Y-axis. (n = 3) (B) ERG expression in sorted cell populations. Q-RT-PCR analysis of RNA isolated from EB cells sorted for VEGF-R2 at day 3.5, and VE-cadherin and CD41 at day 4.5 are shown. ERG is present in the mesodermal/hemangioblast cells expressing VEGF-R2 at day 3.5. ERG is highly enriched in the VE-cadherin expression population, but is almost absent in the CD41⁺ cells at day 4.5. Error bars indicate means +/- S.D. (n = 3)(C) Flow cytometry analysis of ERG expression in EBs at different time points of ES cell differentiation. The increasing percentage of cells expressing ERG over time is shown by the shifting cell population (green) along the x-axis, compared to the ERG negative cells, shown in red. (D) Flow cytometry analysis of ERG expression in relation to other cell-lineage specific markers: hematopoietic (CD41 and Ter119), and endothelial (VE-cadherin) in day 8.5 EBs. Cell population expressing ERG was labeled with green fluorescent marker (FITC) and migrated along the x-axis.