Fig. 5. Ndst1 mutation disrupted Fgf10/Fgfr2b interaction and ectopic lacrimal gland budding. (A-F) LACE assay of FGF/FGFR binding at the lacrimal gland buds. Heparan sulfate mediated Fgf10/Fgfr2b and Fgf7/Fgfr2b binding were observed in the tip of wild-type lacrimal gland buds, but not in that of the Ndst1^flox/flox;Le-Cre mutant embryos (arrow). By contrast, ubiquitous Fgf1/Fgfr2b was present in both wild-type and mutant embryos (arrowheads). (G-L) Ectopic lacrimal gland budding induced by Fgf10. The control explant developed endogenous lacrimal gland in the presence of BSA-containing beads (G, asterisks). By contrast, Fgf10 beads induced additional ectopic lacrimal gland buds in both control and Ndst1^flox/flox;Le-Cre explants (J,K, arrowheads), whereas no buds appeared in the Ndst1/2 double mutants (I,L). (M) Lacrimal budding rate in explant cultures [Fisher's exact test: endogenous budding in control and Ndst1^flox/flox;Le-Cre mutants, P<0.001; ectopic budding in control and Ndst1/2 double mutants (Ndst1^flox/flox;Ndst2^-/-;Le-Cre), P<0.02].