Overexpression of Eda induces formation of supernumerary mammary placodes in the neck and the flank.

(A-F) NF-κB reporter expression was analyzed by X-gal whole mount staining in control and K14-Eda littermates at E11.0 (A), 11.25 (B), E11.5 (C), E12.0 (D), E12.5 (E), and E13.5 (F). In control, a low level NF-κB activity was observed anterior to the fore limb bud whereas the same region in K14-Eda gave rise to supernumerary X-gal positive foci (arrowheads). By E12.5 NF-κB became downregulated in the inter-placodal region in the control embryos whereas in K14-Eda embryos the appearance of supernumerary placodes between buds 3 and 4 started to become apparent at E12.5 and was more pronounced at E13.5 (arrows). (G-H) Whole mount in situ hybridization using digoxigenin-labelled probes specific to Wnt10b (G) and Dkk4 (H) at E11.25. Expression was detected in the emerging mammary placodes, as well as anterior to the fore limb bud (arrowheads) in both genotypes. (Scale bar: 500 μm).