[The role of cholesterol in embryogenesis and the Smith-Lemli-Opitzov syndrom]

The role of cholesterol in cell biology has been known for years. The sight of cholesteol biological function has changed after the discovery that the genetic disorder Smith-Lemli-Opitz syndrome is caused by a defect in cholesterol biosynthetic pathway. Cholesterol has an important role in regulation and modification of Hedgehog proteins, what links cholesterol to early embryonic development. Hedgehog proteins comprise a family of secreted signaling molecules that are essential for embryonic patterning and morphogenesis. The deficit of cholesterol during embryogenesis causes severe abnormalities in SLOS because of disrupt autoprocessing of hedgehog proteins. SLOS is an autosomal recessive disorder of sterol metabolism. The underlying pathogenetic basis for SLOS has been shown to be a deficiency of 7-dehydrocholesterol reductase, which catalyzes the last step in cholesterol biosynthesis. Reduced enzyme activity leads to a deficit of cholesterol and accumulation of precursor sterols. The human 7-dehydrocholesterol reductase gene (DHCR7) is localized on chromosome 11q 12-13.

Spectrum of DHCR7 mutations in Slovak patients with Smith-Lemli-Opitz syndrome and detection of common mutations by PCR-based assays

The Smith-Lemli-Opitz syndrome (SLOS), an autosomal recessive disorder associated with multiple developmental malformations, is caused by a large spectrum of mutations in the DHCR7 gene. Mutations in the DHCR7 gene lead to a 7-dehydrocholesterol reductase deficiency, which is the final enzyme in the pathway of the cholesterol biosynthesis. Reduced cholesterol levels and elevated concentrations of its precursor 7-dehydrocholesterol in plasma and tissues are the major biochemical hallmarks of this disorder. In all patients a biochemical analysis of blood sterols using the gas chromatography/mass spectrometry was performed to confirm the clinical diagnosis of SLOS. We have also determined the mutational spectrum of DHCR7 gene in 17 Slovak patients. We identified six different mutations: nonsense mutation W151X and missense mutations V326L, L109P, G410S, R352Q, Y432C. Mutations W151X and V326L accounted for 76% of the SLOS alleles in Slovak population. The Slovak mutational spectrum is similar to that observed in other Central European countries. We also report simple polymerase chain reaction (PCR)-based assays that allow efficient and rapid mutation analysis.