Fig. 5. Expression of Igf1 and Igfbp5 in wild-type and mutant mouse embryos. (A-F) In situ hybridization on whole-mount E11.5 wild-type (A,C,E), Hoxa2 mutant (B,D) and a2-Six2 transgenic embryos (F) using Igf1 (A,B) and Igfbp5 (C-F) probes. The arrow in A and B indicates the embryonic area where Igf1 is upregulated in the mutant. The arrow in C and D indicates the domain where Igfbp5 expression in the Hoxa2 mutant is lost. In E and F, arrows and arrowheads indicate areas of Igfbp5 expression in the second branchial arch; note the reduced Igfbp5 expression in the second branchial arch of embryos overexpressing Six2. I, first branchial arch; II, second branchial arch. (G) Semi-quantitative RT-PCR on RNA extracted from E10.5 second branchial arches of wild-type (wt) and a2-Six2 (tg) embryos using primers specific for Six2 and Gapdh.