RSH/Smith-Lemli-Opitz syndrome (SLOS) [14] is an autosomal recessive human genetic disease caused by a mutation-induced enzymatic defect in the last step in Chol synthesis, i.e., reduction of the ∆7-double bond of 7-dehydrocholesterol (7DHC) to form Chol, catalyzed by the enzyme, DHCR7 (7-dehydrocholesterol reductase; 3β-hydroxysterol-∆7-reductase, EC1.3.1.21) (Figure 1) [15,16,17,18,19]. Here, DHCR7 is linked to Smith-Lemli-Opitz syndrome.