Biochemical and genetic aspects of 7-dehydrocholesterol reductase and Smith-Lemli-Opitz syndrome

In recent years, several inherited human disorders caused by defects in cholesterol biosynthesis have been identified. These are characterized by malformations, multiple congenital anomalies, mental and growth retardation and/or skeletal and skin abnormalities indicating a pivotal role of cholesterol in morphogenesis and embryonic development. The first recognized and most common of these developmental disorders is Smith-Lemli-Opitz syndrome, an autosomal recessive trait caused by mutations in the DHCR7 gene resulting in a deficiency of the encoded sterol Δ7-reductase, alternatively called 7-dehydrocholesterol reductase (EC 1.3.1.21). This enzyme catalyzes the final step in cholesterol biosynthesis, which is the reduction of the Δ7 double bond of 7-dehydrocholesterol to produce cholesterol.