Fig. 2. Apc1 inactivation induces an ectopic dorsal rim area (DRA) fate. Pupal retinas were stained with antibodies against Homothorax (Hth; green), Elav (blue; marking all photoreceptors) and β-gal (magenta). A svp-lacZ insertion allows demarcation of the dorsoventral equator (indicated by a solid white line in B, D and F). In all panels, dorsal is oriented to the top. (A,B) In wild-type pupal retinas, hth is expressed in all inner photoreceptors in the DRA, as well as in some pigment cells and the head capsule surrounding the retina. Hth expression (dashed white line in B) is restricted to one or two rows of ommatidia at the dorsal edge of the retina, and extends up to, or one ommatidial cluster above, the equator (B). (C-F) In Apc1^Q8 mutant retinas, hth is expressed throughout the dorsal half of the retina, extending up to the equator or to one row above the equator (C,D: 20 hours APF; E,F: 30 hours APF).