Figure 3

Complementary expression pattern of Wif1 and Shh in the cloaca endoderm. Wif1 expression (brown) at the tip of the urs endoderm and the proximal cloaca membrane epithelium was increased from E11 (a) to E12.5 (b) before septation but reduced drastically at E13.5 (c). Shh expression (purple) in the cloaca endoderm and rectum endoderm showed a complementary expression pattern with Wif1. Shh was expressed at the entire cloaca endoderm by E11 (d). Shh was expressed at a very low level in urs and cloaca membrane endoderm, whereas Wif1 was expressed strongly at E12.5 (e) and E13.5 (f). Nuclear β-catenin immuno-reactivity (arrowheads) was localized in the apical urs endoderm when Wif1 expressed weak at E11 (g and g′). At E12.5 and E13.5, nuclear β-catenin immuno-reactivity was only detected in the basal urs endoderm (arrowheads) (h, h′ and i, i′) but not in the apical urs endoderm (h′′ and i′′). 3D reconstruction of Wif1 expression domains at E12.5 showed Wif1 expression in the midline of the septating cloaca (j and j′). Coronal sections of the distal and proximal region of the genital tubercle showed that Wif1 was not expressed in the distal midline ugs endoderm (k) but in the proximal midline endoderm (l). Expression of Shh was detected in the entire distal ugs endoderm (m), but its expression was absent in the proximal midline endoderm (n). White arrowheads indicate the plane of coronal sections. Regions highlighted were magnified as shown. Scale bar: 50 μm