Fig. 8. Loss of FGF signaling in Ndst1-mutant lenses. (A) Specific Erk-P staining in the developing lens. Erk-P was detected in control lenses, but not in embryos treated with MEK- or FGFR-inhibitors. (B) Loss of Erk-P expression in Ndst1-mutant lenses. Erk-P immunostaining was decreased in the Ndst1-mutant lens placode (arrowhead) and lens vesicle (arrow), whereas Pax6 and Pax2 expressions were preserved. (C) The FGF-responsive transcription factor ERM was downregulated in the E10.5 Ndst1 mutant. RNA in situ hybridization showed that ERM was expressed in wild-type, but not in Ndst1-mutant, lenses. The lens vesicle was identified by Pax6 staining the same section. KO/KO, homozygous Ndst1-knockout embryos.