Two Wnt pathways regulate VPC polarization.

<p><b>A</b>. Schematic of vulval precursor cells in the whole animal. <b>B.</b> Schematic of refined (central) and ground (posterior) Wnt signals regulating VPC polarity. <b>C.</b> A schematic of polarized 2°-1°-2° VPC lineages (P5.p (left), P6.p (center), and P7.p (right)). P5.p and p7.p lineages are asymmetric and mirror one another around a central axis (dotted line). (<b>D-F</b>) Illustration and images of vulval lineages, model polarity signals and morphology in animals that are (<b>D</b>) wild type, (<b>E</b>) <i>egl-20(n585)</i> using only refined polarity, or (<b>F</b>) <i>lin-17(n671)</i>; <i>lin-18(e620)</i> using only ground polarity. Arrows represent putative Wnt polarity signals received by VPCs, grayed arrows are inactivated polarity signals, and dotted lines represent central vulval axis.