Development and characterization of a hypomorphic Smith-Lemli-Opitz syndrome mouse model and efficacy of simvastatin therapy.
Smith-Lemli-Opitz syndrome (SLOS) is a genetic syndrome caused by mutations in the 3beta-hydroxysterol Delta(7)-reductase gene (DHCR7). SLOS patients have decreased cholesterol and increased 7-dehydrocholesterol (7-DHC) levels. Dietary cholesterol supplementation improves systemic biochemical abnormalities; however, because of the blood-brain barrier, the central nervous system (CNS) is not treated. Simvastatin therapy has been proposed as a means to treat the CNS. Mice homozygous for a null disruption of Dhcr7, Dhcr7(Delta3-5/Delta3-5), die soon after birth, thus they cannot be used to study postnatal development or therapy. To circumvent this problem, we produced a hypomorphic SLOS mouse model by introducing a mutation corresponding to DHCR7(T93M). Both Dhcr7(T93M/T93M) and Dhcr7(Delta3-5/T93M) mice are viable. Phenotypic findings in Dhcr7(T93M/Delta3-5) mice include CNS ventricular dilatation and two to three syndactyly. Biochemically, both Dhcr7(T93M/T93M) and Dhcr7(T93M/Delta3-5) mice have elevated tissue 7-DHC levels; however, the biochemical defect improved with age. This has not been observed in human patients, and is due to elevated Dhcr7 expression in mouse tissues. Dietary cholesterol therapy improved sterol profiles in peripheral, but not CNS tissues. However, treatment of Dhcr7(T93M/Delta3-5) mice with simvastatin decreased 7-DHC levels in both peripheral and brain tissues. Expression of Dhcr7 increased in Dhcr7(T93M/Delta3-5) tissues after simvastatin therapy, consistent with the hypothesis that simvastatin therapy improves the biochemical phenotype by increasing the expression of a Dhcr7 allele with residual enzymatic activity. We conclude that simvastatin treatment is efficacious in improving the SLOS-associated sterol abnormality found in the brain, and thus has the potential to be an effective therapeutic intervention for behavioral and learning problems associated with SLOS.
Correa-Cerro
Lina S
LS
Unit on Molecular Dysmorphology, Heritable Disorders Branch, National Institute of Child Health and Human Development, Bethesda, MD 20892, USA.
Wassif
Christopher A
CA
Kratz
Lisa
L
Miller
Georgina F
GF
Munasinghe
Jeeva P
JP
Grinberg
Alexander
A
Fliesler
Steven J
SJ
Porter
Forbes D
FD
D016475:3T3 Cells; D000483:Alleles; D019943:Amino Acid Substitution / Q000235:genetics; D000818:Animals; D002478:Cells, Cultured; D003433:Crosses, Genetic; D004195:Disease Models, Animal; D053595:Embryonic Stem Cells / Q000637:transplantation; D005260:Female; D009682:Magnetic Resonance Spectroscopy; D008715:Methionine / Q000235:genetics; D051379:Mice; D008810:Mice, Inbred C57BL; D016297:Mutagenesis, Site-Directed; D044925:Oxidoreductases Acting on CH-CH Group Donors / Q000235:genetics; D010641:Phenotype; D019821:Simvastatin / Q000627:therapeutic use*; D019082:Smith-Lemli-Opitz Syndrome / Q000188:drug therapy* / Q000201:enzymology / Q000235:genetics*; D013912:Threonine / Q000235:genetics
D013912:Threonine; D008715:Methionine; D019821:Simvastatin; D044925:Oxidoreductases Acting on CH-CH Group Donors; C019995:7-dehydrocholesterol reductase