Figure 1. JAK2^V617F-mutant ECs have increased cell proliferation and angiogenesis in vitro compared to JAK2^WT ECs.

(A) As determined by RT-PCR, human JAK2^V617F was expressed in ECs from Tie2/FF1 mice, but not in ECs from control mice. Human erythroleukemia (HEL) cells were used as the positive control. (B) JAK2^V617F ECs proliferated more than JAK2^WT EC (2.0-fold, p = 0.031). Results of 2 independent experiments (with triplicate in each experiments) are shown here. (C) JAK2^WT and JAK2^V617F ECs (6×10⁴) were seeded in Matrigel matrix. EC tube formation was observed after an 8-hour incubation. A representative picture is shown. Magnification: 100×. (D) Quantification of tube formation was performed on images taken at 40× magnification by counting the number of nodes (or branch points), loops, and tubes in 4 non-overlapping fields. Results are expressed as the mean ± SEM (n=4). Data are from one of two independent experiments that gave similar results. (E) The tubular structures formed by the JAK2^V617F ECs in vitro were more stable than the JAK2^WT ECs after 24-hour incubation.