Fig. 2. SoxN regulates Wg pathway activity. (A) Wild-type cuticle pattern shows a normal expanse of Wg-specified naked cuticle separating denticle belts. (B) SoxN^NC14 single mutants produce excess naked cuticle. (C) Wild-type stripes of en expression span 2-3 cells in each segment. (D) en-expressing stripes in SoxN^NC14 are broadened, similar to known phenotypes produced by ectopic Wg signaling. (E) Ubiquitous expression of wild-type SoxN with the arm-Gal4 driver rescues the excess-naked-cuticle phenotype in SoxN^NC14 homozygotes. This treatment does not rescue embryonic lethality. (F) Overexpressing SoxN at higher levels, using the E22C-Gal4 driver in an otherwise wild-type embryo, affects Wgmediated cuticle patterning. Ectopic denticles replace some of the ventral and ventrolateral naked cuticle (arrows), and dorsal patterning is disrupted, leading to curvature of the embryo. We observe an average of 12 ectopic denticles within the naked cuticle zone of a typical abdominal segment (n=100). (G) Stripes of en expression extend evenly from the ventral midline to the edge of the dorsal epidermis in wild-type stage-10 embryos. (H) These stripes are narrowed, particularly in the dorsolateral regions (arrow), when UAS-SoxN is driven with E22C-Gal4. Ventrally, expansion of en expression in the underlying central nervous system (bracket) can be seen; this en expression is not under the control of Wg (Bejsovec and Martinez Arias, 1991; Heemskerk et al., 1991) and presumably reflects the role of SoxN in specifying neuronal fates. (I) Side-by-side comparison showing no difference in anti-Arm staining between a SoxN^GA1192 mutant (bottom) and a wild-type sibling (top). (J) Anti-GFP staining reveals the presence of the twist-GFP balancer chromosome in a wild-type sibling and its absence in the homozygous mutant embryo. (K) Quantitative immunoblot of lysates from hand-selected embryos shows equivalent Arm levels in homozygous mutants for SoxN^GA1192 and SoxN^NC14 compared with their wild-type CyO-GFP-bearing siblings. When normalized to the tubulin loading control, there is no detectable difference among the first three lanes. By contrast, Arm levels are 25% higher in RacGap50C^AR2 mutant homozygotes. Embryos are oriented with anterior to the left and dorsal side up.