Figure 9.

Ultrastructure of basal cells from the back skins and paw skins of K18 transgenic mice bred on either a wild-type or a K14 null background. Skins of 1–2-d-old K18 transgenic mice on either a wild-type or K14 null background were processed for electron microscopy as described in the Materials and Methods. (A) basal cells from K18 transgenic/K14 wild-type back skin, depicting normal keratin filament bundles (kf) and desmosomes (de). Paw skin showed similar morphology. (B– D) basal cells from K18 transgenic/K14 null back skin (B and C) or paw skin (D). The majority of basal cells in back skin displayed normal morphology and keratin filament bundles, similar to that seen in B. An occasional basal cell from back skin exhibited signs of cytolysis (asterisks and small arrowheads), with some regions of the cytoplasm devoid of keratin filaments (large arrowhead in C) and other regions showing some small aggregates or clumps of keratin (C′, kc). Many cells from paw skin displayed prominent clumping of keratin both in the cytoplasm and associated with the desmosomes (D and inset to D, respectively). D′ and D″ show higher magnification to visualize these clumps of keratin in more detail. Note that spinous cells (SP) contained a largely normal keratin network, reflective of the induction of K1 and K10 in these layers. BL, basal lamina; mi, mitochondria; hd, hemidesmosome; Nu, nucleus; BC, basal cell. Bar in A: (A) 0.4 μm; (B, C′, D′, D″) 0.3 μm; (C) 0.9 μm; (D) 0.8 μm; (inset to D) 0.1 μm.