Summary of Wnts, Wnt antagonists, and Fzs receptor expression.

<p>Wnts are expressed in nested domains posteriorly, whereas <i>sfrps</i> are expressed in the anteriormost ectoderm at the blastula and gastrula stages. <i>dkk1/2/4</i> is expressed in three discrete domains of gastrula ectoderm. At juvenile stages, Sfrps are expressed in the very anterior ectoderm (apical tuft), and <i>sfrp1/5</i> is also expressed in the entire proboscis mesoderm, whereas <i>dkk1/2/4</i> is broadly expressed in the anterior ectoderm. Wnts are expressed in three discrete ectodermal domains: the base of the proboscis, the anterior trunk (over the first gill slit), and the posterior-most ectoderm. In addition, <i>wnt9</i> and <i>wntA</i> are expressed in posterior internal tissues. Fz genes are expressed in nested domains along the ectoderm. Territories are color coded: endomesoderm (grey), posterior ectoderm (dark blue), intermediate ectoderm (medium blue) and anterior ectoderm (light blue). Fz, frizzled; Sfrp, secreted frizzled-related protein.