Fig. 6. Ectopic stimulation of the Emx2 enhancer through ectopic activation of Bmp and Wnt signalling. E11.5 mesencephalic tissue was electroporated with the indicated constructs and processed for immunohistochemistry (A,B) or stained for lacZ expression (C-F). (A) Electroporation of a GFP expression vector leads to robust GFP expression in dissected tissue. (B) Co-transfection of the GFP expression vector with a plasmid encoding a Myc-tagged Bmp receptor (ALK3 or Bmpr1a). Expression of both proteins, GFP and Myc-ALK3, is observed in the same cells (arrows). GFP expression was detected by its intrinsic green fluorescence while Myc-Alk3 protein expression was detected by immunofluorescent labelling with an anti-Myc antibody. (C) Electroporation of the reporter plasmid alone does not result in enhancer activity. Co-electroporation of the reporter gene construct together with either constitutive active ß-catenin (D) or activated ALK3 (E) leads to an induction of enhancer activity in few cells (arrowheads). The inserts shown in D,E represent higher magnifications of the boxed areas. (F) The Emx2 enhancer is heavily stimulated after activation of both Bmp and Wnt signalling.
