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. 2010 Sep 17;285(48):37704–37715. doi: 10.1074/jbc.M110.140517

FIGURE 2.

FIGURE 2.

Fusion and cytoplasmic mixing of HEK and CHO cells upon expression of FGFRL1. A, CHO-PgsA cells were transfected with a tetracycline inducible eGFP expression construct, which is only active in the presence of the TetOn transactivator protein and doxycycline. The cells were trypsinized and seeded together with either HEK-TetOn-RL1ΔC, HEK-TetOn-RL1WT cells (express FGFRL1ΔC and FGFRL1 wild type, respectively, in the presence of doxycycline) or with regular HEK-TetOn cells. Doxycycline at 1000 ng/ml was added to all dishes. Note that both HEK-TetOn-RL1 cell lines fused with the CHO cells, leading to the diffusion of the TetOn transactivator from the HEK-TetON-RL1 cells into the syncytial cytoplasm. This activated the expression of eGFP in the large, syncytial cells. No fusion and no activation of eGFP expression was observed with the regular HEK-TetOn cells that served as controls. The image showing the fused FGFRL1 wild-type-expressing cells was taken at a higher magnification. Bar, 100 μm. B, higher powered magnification of a large, syncytial cell consisting of eGFP (green)-transfected CHO and FGFRL1ΔC (red)-expressing HEK-TetOn cells. Note that some FGFRL1-expressing HEK-TetOn cells (red) appear to be attracted by the syncytial cell. Bar, 20 μm.