Fig. 5. Epidermal differentiation markers are expressed earlier in development with normal patterns in K5-Klf4 DTs. Control wild-type and line 2 K5-Klf4 DT epidermis at the age indicated were fixed in paraformaldehyde, embedded in paraffin and sections were stained with epidermal differentiation markers: keratin 14 (K14; basal layer), keratin 1 (K1; spinous layers), loricrin (lor) and filaggrin (fil; granular layers). All of the markers show the normal restriction of expression, but the K5-Klf4 DTs express the terminal differentiation markers loricrin and filaggrin earlier in development. The dotted line indicates the basement membrane.