title: Severe facial clefting in Insig-deficient mouse embryos caused by sterol accumulation and reversed by lovastatin.
abstract: Insig-1 and Insig-2 are regulatory proteins that restrict the cholesterol biosynthetic pathway by preventing proteolytic activation of SREBPs and by enhancing degradation of HMG-CoA reductase. Here, we created Insig-double-knockout (Insig-DKO) mice that are homozygous for null mutations in Insig-1 and Insig-2. After 18.5 days of development, 96% of Insig-DKO embryos had defects in midline facial development, ranging from cleft palate (52%) to complete cleft face (44%). Middle and inner ear structures were abnormal, but teeth and skeletons were normal. The animals were lethargic and runted; they died within 1 day of birth. The livers and heads of Insig-DKO embryos overproduced sterols, causing a marked buildup of sterol intermediates. Treatment of pregnant mice with the HMG-CoA reductase inhibitor lovastatin reduced sterol synthesis in Insig-DKO embryos and reduced the pre-cholesterol intermediates. This treatment ameliorated the clefting syndrome so that 54% of Insig-DKO mice had normal faces, and only 7% had cleft faces. We conclude that buildup of pre-cholesterol sterol intermediates interferes with midline fusion of facial structures in mice. These findings have implications for the pathogenesis of the cleft palate component of Smith-Lemli-Opitz syndrome and other human malformation syndromes in which mutations in enzymes catalyzing steps in cholesterol biosynthesis produce a buildup of sterol intermediates.
authors.affiliation: Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9046, USA.
authors.forename: Luke J
authors.initials: LJ
authors.lastname: Engelking
authors.forename: Bret M
authors.initials: BM
authors.lastname: Evers
authors.forename: James A
authors.initials: JA
authors.lastname: Richardson
authors.forename: Joseph L
authors.initials: JL
authors.lastname: Goldstein
authors.forename: Michael S
authors.initials: MS
authors.lastname: Brown
authors.forename: Guosheng
authors.initials: G
authors.lastname: Liang
mesh_terms: D000818:Animals; D001842:Bone and Bones / Q000187:drug effects / Q000196:embryology; D005260:Female; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors / Q000627:therapeutic use*; D008148:Lovastatin / Q000627:therapeutic use*; D008565:Membrane Proteins / Q000172:deficiency* / Q000235:genetics*; D051379:Mice; D018345:Mice, Knockout; D009056:Mouth Abnormalities / Q000235:genetics* / Q000517:prevention & control; D011247:Pregnancy; D013261:Sterols / Q000378:metabolism
chemical_list: D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; C506119:Insig1 protein, mouse; C506120:Insig2 protein, mouse; D008565:Membrane Proteins; D013261:Sterols; D008148:Lovastatin