Fig. 2

Nkd1 is a target of canonical Wnt/β-catenin signaling. Overexpression of constitutively active β-catenin RNA results in ectopic expression of nkd1 at dome stage (B) compared to uninjected controls (A). Overexpression of axin RNA reduces endogenous nkd1 expression in the mediolateral margin at 50% epiboly (D) compared to uninjected controls (C). Arrowheads point to domains of reduced or absent nkd1 expression. (E–L) Expression of nkd1 at dome stage (E–H) and shield stage (I–L) in wild-type (E, I) and different mutant backgrounds: (F, J) boz^m168, (G, K) maternal zygotic one-eyed pinhead (mzoep^tz57) and (H, L) maternal zygotic silberblick (mzslb^tz215). Note lack of nkd1 expression at dome stage in boz mutants (line in panel F), but an increase in expression in the dorsal region at shield stage (line in panel J). (A, B) dorsal view, animal pole is to the top. (C, D) Animal view. (E–L) Animal view, dorsal is to the right. While there is no change in nkd1 expression at dome stage in mzoep (G), there is a dramatic reduction in nkd1 expression in the dorsal region at shield stage (K). There is no observable difference in nkd1 expression in mzslb compared to wild type (H, L). (M) Relative qRT-PCR values for nkd1 in wild-type and boz embryos at dome and shield stage. Values are normalized to wild-type for both dome and shield stage (wt dome = 1±0.78; boz dome = 0.17±0.15; wt shield = 1±0.18; boz shield = 3.73±0.32). Error bars represent standard deviation (Students t-test, *, p < 0.01; **, p < 0.001).