Fig. 3. The hinge territory is not specified in DNW discs. Wild-type (A-G) and DNW mutant (H-M) wing discs are shown. (A) In early wild-type discs, the spatial pattern of expression of ds-lacZ (red) and Wg (green) is complementary. At the periphery of the Wg domain, cells express ds-lacZ (red) at low levels, and Tsh expression (green; B) is excluded from those cells. At early third instar, ds-lacZ (red; C,D,E), Hth (green; C) and Zfh2 (green; E) are highly expressed in a ring of cells around the wing pouch where Tsh expression (green; D) is excluded. (F) In late third instar, a cross-section along the AP border (dotted line) shows a ring of cells abutting the Nub domain (green) that express ds-lacZ (red) at high levels (yellow arrow); (G) Tsh expression (red) is absent (yellow arrow). In DNW discs, early Wg expression is apparently normal but restricted to the A cells (H), and Ds expression is almost undetectable (I, compare with the control in 2E). (J,K) Only a narrow ring of cells that surround the wing pouch (Nub, red) express specific hinge markers, such as Hth (green; J), and ds-lacZ (green; K). By contrast, Tsh (L) is excluded from the two-cell wide ring (as in G), indicating that Wg activity is decreased. (M) Zfh2 is expressed in a broader ring around the wing pouch cells. (N) Schematic representation summarising the changes observed in DNW (ds^–/–) with respect to wild-type (wt) discs. Different stripes represent the spatial distribution of genes involved in the specification of territories along the PD axis. Low (light) and high (dark) levels of expression are indicated for each gene in different colours. A/P, anterior/posterior; P, proximal wing. Numbers 1 to 5 indicate the folds of a mature wing imaginal disc. RI, RII and RIII correspond to the three concentric rings around Nub domain.