Fig. 1. dx is indispensable for the normal activation of N signaling at the DV boundary. (A) Wild-type adult wing. (B) Adult wing of dx²⁴/Y, a hypomorphic loss-of-function mutant of dx, showing recessive distal wing-blade notching (arrowhead). (C,E) Wg expression in the wild-type third-instar wing disc, detected in a narrow stripe along the DV boundary by an anti-Wg antibody (green). E is a higher magnification of C. (D,F) Wg expression (green) in the dx²⁴/Y third-instar wing disc, showing a reduction in the Wg protein at the intersection of the AP and DV boundaries that corresponds to the distal tip of the wing (black and white arrowhead in B,D,F). F is a higher magnification of D. (G,I) Cut expression in the wild-type third-instar wing disc, detected in a narrow stripe along the DV boundary by an anti-Cut antibody (green). I is a higher magnification of G. (H,J) Cut expression (green) in the dx²⁴/Y third-instar wing disc, showing an interruption at the intersection of the AP and DV boundaries that corresponds to the distal tip of the wing (black and white arrowheads in B,H,J). J is a higher magnification of H. (K) Schematic diagram of the vgBE-lacZ transgene constructs. Wild-type recognition sequences for Su(H) and its mutant derivative are shown in the upper and lower lines, respectively. Mutated nucleotides are shown in red. (L-N) Activation of vgBE at the DV boundary of the third-instar wing disc detected by vgBE-lacZ (green). (L) A wing disc of vgBE-lacZ. (M,N) A wing disc of vgBE-lacZ overexpressing Dx^Pro (purple) under the control of ptc-GAL4 at 18°C, showing suppression of vgBE activity in the region overexpressing Dx^Pro (white arrowhead). M and N show a single green channel and a merged image, respectively.