Figure 2. Histological and ultrastructural abnormalities of Ogna mouse skin.

(A) Epoxy resin-embedded and toluidine blue-stained skin sections from 1-day-old mice. Asterisks indicate trauma-induced blister formation between stratum basale (sb) and dermis (d), not observed in Plec ^+/+ mice. sc, stratum corneum. (B) Transmission electron microscopy of skin lesions. Arrowheads indicate intact HDs with attached keratin filament bundles (arrows) aligned along the basal cell membrane of basal keratinocytes in wild-type skin, and remnants of HDs lacking keratin filaments at blister (*) floors in mutant skin. (C,D) High magnification electron micrographs of intact skin sections of newborn (C) and adult (D) mice. (E) Outlines of HDs (grey bars) distributed along the basal cell membrane of basal keratinocytes (black lines) in panels D. Note reduced numbers and smaller sizes of HDs (arrowheads in C and D) in mutant, compared to Plec ^+/+ skin; also, few HDs in mutant skin have attached keratin filament bundles, whereas thick bundles of filaments attached to HDs are dominant in Plec^+/+ skin (arrows in C and D). d and e (B–E), dermis and epidermis, respectively. Bars, 20 µm (A); 500 nm (B–D). (F,G) Morphometric analysis of HD numbers (average percentage of cross-sectioned basal cell membrane of basal keratinocytes containing HDs) (F) and keratin filament attachment (G) in adult mouse skin. A total length of 55–60 µm of basal cell membrane of basal keratinocytes was analyzed in electron micrographs of foot pad skin sections from wild-type and mutant littermates (n = 5, total numbers of HDs scored: Plec^+/+, 617; Plec^Ogna/+, 590; Plec^Ogna/Ogna, 605). Box and whisker plots indicate the median (middle line in the box), the mean (small crosses), 25^th percentile (bottom line of the box), 75^th percentile (top line of the box), and 2.5^th and 97.5^th percentiles (whiskers). *** P<0.001, one-way ANOVA with Tukey post test for multiple comparisons.