FIGURE 1.

Fatp4 is expressed in skin and its appendages. A–F, dorsal skin sections from control and Fatp4^−/− littermates at the indicated stages were subjected to in situ hybridization with Fatp4 riboprobe and counterstained with nuclear fast red. Fatp4 RNA, first detected in the epidermis of normal embryos at E15.5 (A), was found in suprabasal keratinocytes and epithelium of hair follicle progenitors (asterisk) at E16.5 (C), and was down-regulated in the epidermis and hair follicles but detected in sebocytes (arrowheads) at birth (E). In Fatp4 mutants, Fatp4 RNA was not detected at E15.5 (B) but was observed in nuclei at E16.5 (D) and at birth (F). G and H, immunohistochemistry with antiserum to FATP4 at E17.5. FATP4 was detected primarily in the granular layer of the epidermis (arrow) and in sebocytes (arrowhead) in controls (G), whereas only background activity was detected in mutants (H). Dashed lines demarcate the dermo-epidermal boundary. Bar is 50 μm.