Overexpression of Apically Localizing Fz1/2 Chimeras Has an Inhibitory Effect on Canonical Wnt Signaling

<div><p>(A–D) show adult wings of the respective genotypes. Anterior is up and distal to the right.</p> <p>(A) Adult wing of an <i>en-Gal4/+; UAS-fz1–1-1/+</i> fly (<i>en>fz1–1-1</i>). <i>en-Gal4</i> drives UAS reporter genes only in the posterior compartment. Inset shows high magnification of region marked by arrowhead. Some wing margin bristles are missing (arrow) in the posterior compartment. The border between anterior (“a”) and posterior (“p”) compartments is marked with black line.</p> <p>(B) <i>dsh^V26/+; en>fz1–1-1</i> adult wing. Note enhancement of the margin bristle phenotype: all margin bristles are missing from the area between the arrows in the posterior compartment.</p> <p>(C) <i>en>fz2–1-1</i> wing. Most of the wing margin bristles are missing in the posterior compartment. Note also that the posterior compartment is smaller.</p> <p>(D) <i>en>fz2–2-1</i> wing. Again the posterior compartment is smaller and most of the margin is missing.</p> <p>(E–G) show that Fz1–1-1 expression increases apical localization of Dsh-GFP and reduces Dsh-GFP in more basolateral areas of wing cells. (E) and (F) are xy-horizontal optical sections, and (G) is an xz-cross section. The positions of (E) and (F) sections are indicated in (G).</p> <p>(E) Apical xy-optical section of a third instar wing disc. Fz1–1-1 (red) is overexpressed by <i>en-Gal4</i> in the posterior compartment (anterior–posterior border is labeled by white line, and the corresponding compartments are labeled “a” and “p,” respectively). Dsh-GFP (green) accumulates at higher levels apically in the posterior compartment. Single-channel Dsh-GFP staining is shown at right. In wild-type disc, Dsh-GFP is evenly distributed with no anterior–posterior bias (not shown).</p> <p>(F) A more basal xy-section of the same disc as in (E). Note reduction of Dsh-GFP staining in the posterior compartment, except at the apical junctions as seen in folds (arrowhead). In the anterior compartment, where Fz1–1-1 is not overexpressed, Dsh-GFP is only slightly enriched in the apical folds (arrow).</p> <p>(G) xz-section of the same wing disc shown in (E) and (F), with top panel showing double labeling for anti-Myc (red) and anti-Dsh-GFP (green) and bottom panel showing single channel of Dsh-GFP staining.</p> <p>(H) xz-section of a comparable disc expressing Fz2–1-1 in the posterior compartment<i>.</i> Fz2–1-1 overexpression (red) also causes accumulation of Dsh-GFP in apical junctions and reduction of Dsh-GFP along the basolateral region.</p>