Fig. 3. EXT genes are required for Hh signaling. dpp-lacZ expression (gray on the left panel) and Ptc protein level (gray on the middle panel) in the wild-type and mutant wing discs. Some of mutant clones are marked by light-blue lines for clarification. (A) In the wild-type wing discs, dpp expression is induced by Hh that emanates from the posterior compartment and is detected as far as 15 cells away from the anterior-posterior boundary, and Ptc protein can be detected as far as five cells away. A schematic diagram is shown on the right panel. (B) In the botv⁴²³ clone (marked by the absence of GFP on the right panel), dpp (red in the right panel) and Ptc (blue in the right panel) levels are reduced (arrows), and cells located at the posterior part of the clone still respond to Hh signal. The reduction in dpp expression extends to the wild-type cells anterior to the mutant clone (arrowhead). (C) In the sotv³²⁶ mutant clone, Ptc protein and dpp expression levels are reduced slightly (arrow), indicating that Hh signaling is not severely impaired. (D,E) Loss of botv (D) or sotv (E) activity in the posterior compartment does not affect dpp level in anterior cells (arrow). However, Ptc protein level was sometimes slightly decreased in the anterior cells along the AP boundary (D,E).