Fig. 1. HB-EGF expression during eyelid development. (A-E) Whole-mount lacZ staining of HB^del/+ eyelids (black arrow) at (A) E14.5, (B) E15.0, (C) E15.5, (D) E16.0 and (E) E16.5. The densely blue zone (asterisk) is the iris. (F-J) lacZ and Hematoxylin/Eosin stained sections of HB^del/+ eyelids at (F) E14.5, (G) E15.0, (H) E15.5, (I) E16.0 and (J) E16.5. (K-O) Schematic illustration of eyelid development. (K) At E14.5, leading edge formation has still not occurred. (L) At E15.0, the leading edge starts to extend from the eyelid root on both sides. (M) At E15.5, extension of both the leading edge and the root region continues (arrowheads). (N) At E16.0, the leading edges from both sides contact each other. (O) At E16.5, the root regions migrate and contact each other. (G-J) The expression of HB-EGF is restricted to the tip of the leading edge during this process. Scale bars: 500 µm for A-E; 100 µm for F-J.