FIG. 3.

Activity of the C40 enhancer in developing tissues. At E15.5, enhancer activity was present in the developing digits, whiskers, and snout skin, as well as in the external genitalia (B and C); no expression was detected in the wild-type counterpart (A). (D) Histological sections were obtained after β-galactosidase staining and were subsequently paraffin embedded and counterstained with eosin. Staining was present in the olfactory and oral epithelium, in the tooth bud and in the atrium. (E) An adjacent section from the same embryo was immunostained using anti-p63 antibodies, after β-galactosidase staining. Arrows indicate p63-expressing tissues and/or the C40 enhancer activity. In newborn transgenic mouse skin the enhancer activity was exclusively localized in the epithelial component, with intense β-galactosidase staining in the hair follicle, and weaker staining in the epidermis (G), whereas no staining was detected in wild-type littermates (F). Scale bar, 50 μm.