Ultrastructural defects in Abca12^el12/el12 mice.

Thin sections of Abca12^el12/el12 epidermis illustrated hyperkeratosis and expansion of the stratum granulosum (A). Nile red staining shows reduced intercellular lamellae lipids at E18.5 (B). In wild type epidermis intercellular lipid lamellae (white arrow and inset) were noted as well as LBs fusing with the surface of granular cells (red arrow) (C). Lamellar bodies in wild type and heterozygous embryonic epidermis were normally loaded with lipid (D). In mutant skin, LBs lacked lamellar cargo (E, F arrowheads) but fused with the granular cell membrane (F; arrows). Mutant epidermis had a normal cornified envelope (G,H) with persistent corneodesmosomes in distal layers of the stratum corneum (G, H, red arrowheads) and the cornified layer had multiple lipid inclusions (G, black arrowheads). Unlike the uniform contents of wild type cornified cells mutant cell layers contained vesicular fibrillar structures (I, red arrows) and frequent inclusion bodies (I, black arrows). EM scale bars in C–F, H, I equal 200 nm and 2 µm in G. C–F and I were stained with ruthenium tetroxide, G and H with osmium tetroxide.