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Fig. 8. Transient transfection with Crk mutant reverses morphological changes induced by gastrin. A and B, CHO cells expressing CCKBR (CHO-CCKB) were grown on culture dishes, serum-starved for 18 h (2% FCS), and then incubated for 24 h in the absence (A) or in presence (B) of 10 nM gastrin. Cells were photographed on an inverted phase-contrast microscope. Bar (A and B), 50 µm. C-F, cells were seeded on coverslips and transiently transfected with the EYFP coding plasmid alone (C and D) or together with 1 µg of the dominant negative mutant of CrkII (E and F). After serum starvation, cells were incubated for 24 h in the absence (C) or presence (D-F) of 10 nM gastrin. Cells were fixed and analyzed for EYFP fluorescence (C and D). Proper expression of the mutant protein was verified by performing anti-CrkII immunofluorescence staining and analyzing CrkII-positive cells for EYFP fluorescence (E and F). Bar (C and D), 60 µm; bar (E and F), 120 µm. G, cells were transiently transfected with either 0 (control), 0.5, 1.0, or 1.5 µg of dominant negative mutant of CrkII-encoding plasmid (Crk-) together with 0.5 µg of EYFP-encoding plasmid and stimulated with 10 nM gastrin for 24 h. Cells were scored for the ability to generate long extensions as described in "Materials and Methods." Arrows point toward elongated cells in B and D and toward short cells in A, C, E, and F.