Fig. 1. Cuticle phenotype and expression pattern of SoxN. (A-B') SoxN mutants have an aberrant cuticle phenotype. (A) Wild type (wt); cuticle of first instar larva. (A') Wild type; single denticle belt. (B) SoxN^GA1192 mutant; cuticle of first instar larva. (B') SoxN^GA1192 mutant; single denticle belt. Numbers (1-6) represent the six rows of denticles. (C-J) Expression pattern of SoxN and its regulation by signaling pathway activities. (C-E) Wild-type embryos double-stained with anti-SoxN (black) and anti-En (brown). (C) Stage 8; SoxN protein expression is ubiquitous. (D) Stage 9; SoxN expression decays in a narrow stripe just anterior to the En domain. (E) Stage 13; SoxN expression is restricted to segmental stripes, each with a width of six cells. (F) Stage 15 enGal4-UAS-taulacZ embryos double-stained with anti-SoxN (red) and anti-ß-galactosidase (green, detecting En expression). The anterior-most row of SoxN-expressing cells (1) corresponds to the posterior row of En-expressing cells. Arrows, notice that SoxN expression in the two posterior-most rows (5,6) is higher than in the anterior four rows (1-4). (G) Staining of stage-15 wg^cx4 mutant embryos with anti-SoxN; notice that SoxN expression is derepressed as compared with wild type. (H) Staining of stage-15 wg^cx4 embryos with an svb-specific RNA probe; notice that the expression patterns of SoxN and svb in wg^cx4 embryos are highly similar. (I) Staining of stage-15 armVP16Gal4-UAS-Egfr^Act embryos with anti-SoxN; notice that SoxN expression expands posteriorly by two to three rows of cells. (J) Staining of stage-15 armVP16Gal4-UAS-Egfr^DN embryos with anti-SoxN; notice that SoxN expression is reduced. Cartoon: schematic representation of the ventral epidermis with the expression patterns of the wg, en, svb and SoxN genes. SoxN and svb are co-expressed in six rows of cells, which differentiate to produce denticles. SoxN and svb expression is stimulated by Der- and repressed by Wg-pathway activities.