Fig. 1. Effect of different mutants of Cos2 on dpp-lacZ expression. (A,B) dpp-lacZ reporter expression at the AP boundary in wild-type third instar larval discs. Nuclear ß-galactosidase is immunofluorescently labeled (red). Area in A (white box) is shown at higher magnification in B. (C,D) Overexpression of cos2GFP using the 71B Gal4 driver (green) represses dpp-lacZ expression (red) at the AP boundary. (E,F) A small FLP-out clone expressing Motor-GFP (green) in the anterior compartment ectopically expresses dpp-lacZ (red) in a cell-autonomous manner. A region of normal dpp-lacZ expression at the AP boundary is shown (arrowhead). (G,H) An anterior FLP-out clone of cells expressing Neck-GFP (green) ectopically expresses dpp-lacZ (red) in a cell-autonomous manner. (I,J) Cos2C-GFP expression (green) driven by 71B Gal4 represses dpp-lacZ expression (red) at the AP boundary. (K,L) A large FLP-out clone expressing S182N-GFP derepresses dpp-lacZ expression within the clone (red) in a cell-autonomous manner. Box in K indicates the area that is shown at higher magnification in L. The normal expression of dpp-lacZ at the AP boundary is shown in K (yellow arrowhead). Overgrowth of anterior tissue caused by the clone is indicated (white arrow). A posterior clone, which does not ectopically express dpp-lacZ or produce overgrowth of tissue, is also indicated (blue arrowhead). Because not all nuclei in the disc lie in the same optical plane, there appear to be variations in dpp-lacZ staining in different parts of the disc. Correcting this by focusing on small local areas of the disc confirms that dpp-lacZ is expressed at uniform, high levels throughout S182N-expressing clones (data not shown). (M,N) A FLP-out clone expressing S182T-GFP at the AP boundary (green) that interrupts the normal region of dpp-lacZ expression represses dpp-lacZ expression (red) in a cell-autonomous manner. Box in M indicates the area that is shown at higher magnification in N. (O) A chart summarizing the effects each mutation has on dpp-lacZ expression in either the anterior compartment of the disc or at the AP boundary where dpp-lacZ is normally expressed. +++ indicates high uniform levels of derepression or repression. Also shown are schematic drawings of the putative Cos2 homodimer with appropriate alterations to reflect each mutation or deletion. Results were the same for each construct and its C-terminally fused GFP counterpart except for Motor, for which Motor-GFP expressing flip-out clones could not be generated. For this and all other figures, wing discs are oriented such that anterior is leftwards and dorsal is downwards.