Shh and BMP4 expression in Spry CKO eyelids. 35S-labeled BMP4 (A–B′) and Shh (C–D′) riboprobes were hybridized to sections of E14.5 Cre- and Spry CKO mutant embryos. The dotted lines delineate the boundary between the epithelial and mesenchymal cells. A′–D′ are higher magnifications of boxed regions in A–D. BMP4-positive mesenchymal cells in Spry CKO eyelids were clustered near the anterior margin (A, A′, white arrows) but appeared disaggregated in Cre- eyelids (B, B′, white arrows). Conjunctival epithelial cells at the margin showed reduced expression of Shh (compare D and D′ to C and C′ respectively). Green arrows in B and B′ mark BMP4 expression in the hair follicles of the skin. Staining in the retinal pigmented epithelium (rpe) is an artifact of dark-field illumination. Abbreviations; bc, bulbar conjunctiva; l, lens; pc, palpebral conjunctiva; pe, palpebral epidermis; r, retina. Scale bar in (C′): (A–B′, C, D) 100 μm; (C′–D′) 50 μm.