Defects in skin lipid composition and cellular lipid efflux mediated by Abca12.

<p>Analysis <i>Abca12^el12/el12</i> epidermal lipids indicate significant increases in levels of ceramide (Cer), glucoslyceramide (GC), sphingosine (Sph) and free cholesterol in <i>Abca12^el12/el12</i> skin at E18.5. Total phosophatidylcholine (PC) and cholesterol ester (CE) levels were unchanged (A, ***p<0.0001; **p<0.001; *p<0.01 versus wilt type epidermis) (A). Defects in fibroblast cholesterol efflux were assayed using [³H]cholesterol and incubation in the presence (+) or absence (−)) of the LXR agonist TO-901317. Means plus or minus standard deviation of quadruplicate determinations are shown. (**p<0.001 versus non activated cells; ^*# p<0.001 versus ABCA12^+/+ cells; ^*p<0.01 versus ABCA12^−/+ cells) (B). Expression of Abca1 was determined at the protein level by Western blotting (C, upper panel) and decreases in <i>Abca12</i> homozygous mutant cells were shown to be in part due to decreases in transcription of <i>Abca1</i> (C, lower panel, fold change in transcription relative to el12/el12, ***p<0.0005). Lipid accumulation in fibroblasts the presence or absence of the lipid donor acetylated LDL (AcLDL) was assayed by Oil Red O staining (magnification ×100) (D).