Fig. 4. Expression of Gli1 and gremlin is altered in the forelimbs of prx1cre;Ift88^fl/n conditional mutants. Whole-mount in situ hybridization analysis of Gli1 (A-D) and gremlin (E-H) expression in wild-type (A,C,E,G) and prx1cre;Ift88^fl/n (B,D,F,H) forelimbs at E10.5 (A,B,E,F) and E11.5 (C,D,G,H). At E10.5, Gli1 expression is similar in conditional mutants (B) and wild-type controls (A). At E11.5, the expression of Gli1 is retained in wild-type controls (C) but is almost completely absent in conditional mutants (D), except small patches of cells expressing Gli1 can occasionally be seen in prx1cre;Ift88^fl/n mutants (arrowhead). Gremlin expression is restricted to the posterior mesenchyme at E10.5 in wild-type forelimbs (E) but is expanded into the anterior mesenchyme in prx1cre;Ift88^fl/n conditional mutants (arrowhead in F). Expression of gremlin is minimal in wild-type forelimbs at E11.5 (G). By contrast, in prx1cre conditional mutant forelimbs (H), ectopic anterior expression of gremlin is maintained (arrowhead in H). Anterior is up in all panels.