Fig. 2. Apterous regulates msh expression. (A-D) msh expression in third instar wing discs using an msh antisense RNA probe. d, dorsal; v, ventral. (A) Wild-type. Levels of msh expression are low in the dorsal compartment of the wing pouch, except along the dorsal anterior wing margin where expression is higher. In addition, a small patch of msh expressing cells is observed in the ventral compartment (in the anterior mesopleura, arrow) and in the dorsal notum. (B) dpp-Gal4 UAS-apterous disc. dpp-Gal4 is expressed adjacent to the AP boundary in the anterior compartment. Ectopic expression of msh in the ventral compartment is indicated by a red star. The level is comparable to the low dorsal level. Note the difference between the ectopic msh expressing tissue and the normal ventral tissue adjacent to the anterior mesopleura (arrow). (C) apterous mutant disc. apugo is a null allele. Expression of msh is lost in the dorsal compartment, but not in the anterior mesopleura (arrow) and part of the notum. (D) Dlw1/+ disc. msh expression is lower in the dorsal wing pouch. In situ hybridizations to msh were done in parallel in A and D. (E) msh-lacZ expression in a wild-type late third instar wing disc visualized by anti-ß-gal (red). (F) msh-lacZ expression in a wing disc expressing dLMO under patchedGal4 control. patchedGal4 is expressed in anterior cells adjacent to the AP boundary and directs high levels of dLMO expression (green). Endogenous dLMO is expressed at moderate levels in dorsal cells and at low levels in ventral cells. (Right) Repression of msh-lacZ in the patchedGal4 domain is indicated by an arrow. A, anterior; P, posterior.