Fig. 1. Sterols in cholesterol defective mice. (A) Structure of lanosterol, lathosterol, dehydrocholesterol, and cholesterol, depicting a difference of one double bond between cholesterol and lathosterol, and of the location of the double bond in cholesterol and lathosterol (C5-C6 versus C7-C8, respectively). Lanosterol is an early precursor requiring multiple enzymatic steps before its conversion to cholesterol. (B) Biochemical analysis of sterol content in Dhcr7^-/- mouse pancreas. 7-DHC, lathosterol and 8-DHC levels were measured in wild-type, heterozygous and mutant pancreatic tissue from newborn litters. In control animals, (Dhcr7^+/+, Dhcr7^+/-), cholesterol is the major sterol component and constitutes 99% of total sterols. In Dhcr7^-/- mice, 7-DHC is elevated to constitute 58% of all sterols, concomitant with significant elevations of 8-DHC and lathosterol. ^***P<0.001. Values are mean ± s.e.m. of five animals per genotype. (C) Biochemical analysis of sterol content in Sc5d^-/- mouse pancreas. In Sc5d^-/- animals, lathosterol makes up 70% of sterols analyzed, and cholesterol levels are significantly diminished compared with levels in the control. ^***P<0.001. Values are mean ± s.e.m. of nine animals per genotype.