Fig. 3. Eyelid defects in Fgf10-null mice. (A,C) Lateral views of the face from wild-type (A) and Fgf10^–/– (C) mice at birth. (B,D) Histology of the eyes of Fgf10^+/– (B) and Fgf10^–/– (D) mice at birth. The upper and lower eyelids are at the left and right, respectively. The Fgf10^+/– neonate eyelids are fused (arrow in B), while the Fgf10-null eyelids are wide apart (arrowheads in D). The involution of the retina in D is an artifact. (E-S) HE staining of the coronal eye sections from wild-type (E,F), Fgf10^+/– (I-K,O,P), and Fgf10^–/– (G,H, L-N, and Q-S) embryos at E11.5 (E-H), E13.5 (I-N) and E16 (O-S). (E-H) The arrows in E and G indicate the developing eyelid groove. The epidermal cells at the bottom of the lower groove (arrowhead in F) have become cuboid by this stage in the wild-type mice, while they remain flat in the Fgf10-null mice (arrowhead in H). (I-N) The eyelid protrusion (arrowheads) is smaller, and the eyelid groove (arrows) shallower, in the Fgf10-null fetuses. (O-S) The arrowheads in O,Q indicate the eyelid leading edge. Eyelid closure is disrupted in Fgf10-null fetuses. (P) The junctional region of recently fused eyelids of the Fgf10^+/– fetus consists of a loose grouping of cells overlaid by periderm cells (p), which appear to be spilling out onto both the internal and external surfaces. (R,S) The first sign of leading edge cells extending across the corneal surface can be seen in one primitive eyelid (asterisk in S) but not in the other for the Fgf10-null fetus. The arrows indicate the basal layer of the eyelid epidermis, which has spindle-shaped nuclei in P and round ones in R. m, mesenchyme. Scale bars: 250 µm (B,D); 100 µm (E and G, F and H, I and L, J,K,M and N,O and Q); 25 µm (P,R and S).