Fig. 7. Reduction of FGF and FGFR binding to the Ndst1 lens. (A) Reduced FGF2 binding to Ndst1-mutant embryos. Biotinylated FGF2 (1:10,000 dilution) was incubated with lens sections and assayed by immunohistochemistry in wild-type embryos. Significant FGF2 binding in the Ndst1 mutant was observed only with high concentrations of FGF2 (1:1000 dilution). (B) Diminished FGF-FGFR binding on Ndst1-mutant lenses. Ndst1-mutant lenses exhibited reduced binding to FGF8b-FGFR2c and FGF8b-FGFR3c, whereas FGF19-FGFR4 remained the same for wild-type and mutant embryos. (Arrow indicates weaker staining in retina; arrowhead indicates strongly reduced staining in lens.) (C) Requirement of Ndst1 for multiple FGF-FGFR interactions. Ndst1 mutation disrupts some of the FGF-FGFR interactions on the cell surfaces of the lens (+), but not others (-). ^*Weak binding. NB, no binding. KO/KO, homozygous Ndst1-knockout embryos.