Fig. 4. Phenotype of brk point mutants and CtBP and gro mutants. Third instar wing discs containing mutant clones, marked by the loss of a ubiquitous GFP transgene, and stained for omb (lacZ, anti-ßgal), Sal (antibody) and/or vg-QE (lacZ, anti-ßgal) expression. (A,B) brk^F124 clones show ectopic expression of Sal and omb within the wing pouch (arrow), and expansion of the vg-QE domain. (C) brk^F138 clones. (D) Detail from boxed area in C, showing a large clone in the posterior compartment. The edge of the normal Sal and omb domains are shown in red and blue, respectively, in part i, and in white in parts ii and iii (these are approximations). If this were a null mutant clone, Sal and omb would be expressed in all of the mutant cells in the wing pouch, and omb would extend outside of the pouch (see A). However, there is no ectopic omb expression in brk^F138 mutant cells, apart from possibly an expansion to one or two cells wider than normal (note, omb is on the same chromosome as brk, so that omb expression is upregulated in brk mutant cells within its endogenous domain because these cells are now homozygous for the omb enhancer trap). There is some ectopic Sal expression, but only in mutant cells within the endogenous omb domain (arrow in part ii) and not more laterally. (E) vg-QE expression is expanded laterally in some brk^F138 clones (arrow). (F-H) CtBP gro double mutant clones are similar to those of brk^F138, only showing ectopic Sal expression (F, arrow) immediately adjacent to the endogenous domain (when located in the omb domain, not shown). By contrast, Sal is not ectopically expressed in any CtBP single mutant clones (G), whereas there is an occasional, minor deregulation of Sal in gro clones (H, arrow).