FIGURE 6.

ADAM9 is strongly expressed in the epidermis and in the outer root sheaths of hair follicles. Immunofluorescence staining of wild type (a, c, d, and f–h) and Adam9^−/− skin sections (b and e) with an anti-ADAM9 ectodomain antibody is shown. Green, FITC staining of ADAM9; blue, 4′,6-diamidino-2-phenylindole cell nucleus counterstaining. ADAM9 expression is localized to the epidermal keratinocytes and interfollicular keratinocytes of hair follicles (a). This staining pattern for ADAM9 was not seen in Adam9^−/− skin where only minor unspecific staining in the surface stratum corneum and in hair was observed (b). Immunostaining of longitudinal skin sections of anagen stage hair follicles showed ADAM9 staining in keratinocytes of the outer root sheath (c). ADAM9 immunoreactivity in wild type epidermis (d and f–h) and murine Adam9^−/− epidermis (e) is shown. Wild type epidermis (d and g) and hair follicles (f and h) are shown at higher magnification. E, epidermis; D, dermis. ADAM9 reactivity is distributed all over the epidermis and the outer root sheath of the hair follicle. Both contain solitary cells with high ADAM9 expression that are most likely basal keratinocytes near the basement membrane (d and f–h; indicated by white arrowheads). Scale bar, 100 μm.