FIGURE 1.

Proliferation of basal keratinocytes is increased in the skin of γ1III4-deficient mice. In histological sections, embryonic skin (E18.5) of control (a) and γ1III4-deficient (b) mice show a comparable epidermal morphology, including skin appendages. Immunohistochemistry of skin sections with antibodies against Ki67 (c and d) shows statistically significant higher numbers of proliferating cells in the basal compartment of the interfollicular epidermis of mutant mice (d). The number of proliferating cells was quantified by counting Ki67-positive cells in 10 high power fields (40×) per section in 10 individual control and mutant mice (g, n = 10; p = 0,0001). White bar, controls (γ1III4^+/+); black bar, mutants (γ1III4^−/−). Immunohistochemistry of skin sections with antibodies against keratin K14 shows a uniform staining of the basal cell layer in control (e) and mutant (f) mice; E, epidermis; D, dermis. The hair follicle is indicated by an arrow in b. Scale bars, 100 μm (a–d) and 25 μm (e and f).