Lens fiber differentiation in Spry mutant embryos. In situ hybridizations (A, B, E, F) and immunohistochemistry (C–D′, G–H′) were performed on E15.5 control (Cre−) and Spry mutant embryos to detect expression of Prox1 (A–D′) and p57KIP2 (E–H′). In situ hybridizations were performed using 35S-labeled riboprobes (A, B, E, F). Prox1 (B, D, D′, arrows), and p57KIP2 (F, H, H′, arrows) were upregulated in Spry mutant lens epithelial cells. Some of the stalk cells also expressed p57KIP2 (H′, yellow arrow). ce, corneal epithelium; le, lens epithelium; lf, lens fibers; r, retina. Scale bar in (G′): (A–D, E–H) 60 μm; (C′, D′, G′, H′) 10 μm.