Wnt pathway genes are upregulated already at E12.5 in the region where supernumerary mammary placodes form.

<p>Expression of (A) <i>Wnt10b</i>, (B) <i>Wn10a</i>, (C) <i>Kremen2</i>, (D) <i>Lgr4</i>, (E) <i>β-cat</i>, (F) <i>Tbx3</i>, and (G) <i>Nrg3</i> in <i>Eda</i>-/-, wild-type and <i>K14-Eda</i> embryos. Note correlation of levels of <i>Wnt10b</i>, <i>Wnt10a</i>, <i>Kremen2</i>, and <i>Lgr4</i> with the Eda status (A-D).Further, <i>Wnt10b</i>, <i>Kremen2</i>, <i>Lgr4</i>, and <i>β-cat</i> show an early stripe-like expression pattern in the region where supernumerary mammary placodes emerge (A, C-E). (Scale bar: 500 μm.)