Fig. 4. hh and dpp activity are required for squamous morphogenesis in the wing PE. In each panel, confocal sections from top to bottom are of the PE (A-F) and disc cross-section (A'-F'). Red arrows in A-F indicate cross-section levels in A'-F'. Red lines indicate region of squamous cells in A'-C',F'. AP compartment boundary (yellow lines) in the PE (A-F). (A,A') Control disc from larvae heterozygous for wg^IL (wg^IL/CyO y⁺). (B,B') Discs that lack wg activity (wg^IL/wg^IL) are small yet form squamous PE cells and columnar DP cells (B') (n=22 discs). (C,C') Control disc from larvae heterozygous for hh^ts2 (hh^ts2/TM6B). (D,D') In the absence of hh function (hh^ts2/hh^ts2), discs lack squamous PE cells, while DP cells become columnar (D') (n=46 discs). (E,E') Discs from hh^ts2 larvae that overexpress cyclin-D-Cdk4 are larger than discs from hh^ts2/hh^ts2 larvae yet squamous cells do not form (E') (n=26 discs). (F,F') Discs from hh^ts2 larvae that overexpress dpp restores squamous morphogenesis in the PE (F') (n=34 discs). (G,G',H,H',I-K) Ubx>dad wing discs have aberrant squamous morphogenesis. Panels from top to bottom are confocal sections in plane of DP and disc cross-section. Red arrows in G,H indicate cross-section levels in G',H'. Red lines indicate region of squamous cells in H'. (G') A PE that consists entirely of cuboidal-shaped cells and (H') a PE with limited squamous cells apposed to clefted folds in the DP. (I-K) Cross-sections of Ubx<dad wing discs, shows that the AP compartment boundary in the PE (red and yellow arrowheads) fails to shift in the absence of squamous morphogenesis (compare with Fig. 3C). (I) -Spectrin staining. (K) En expression. (J) Overlap of I,K. Scale bar: 50 µm.