These Dhcr7Ex8 mutant mice may be useful in studying Smith-Lemli-Opitz/RSH Syndrome (SLOS; a birth-defect mental-retardation syndrome) or other metabolic disorders involved with cholesterol biosynthesis.
Shailendra B Patel, Medical College of Wisconsin
Mice homozygous for the Dhcr7Ex8 allele lack the exon 8 coding sequence and flanking splice acceptor site of the targeted gene, resulting in the truncated DHCR7 mutation most frequently observed in Smith-Lemli-Opitz/RSH Syndrome (SLOS) patients (IVS8-1G > C). Although a truncated product is transcribed from the targeted gene, no mRNA containing the deleted 3'-coding region is detected in homozygous liver or brain tissue. Homozygous mice exhibit the same biochemical defects as observed with SLOS patients, including markedly reduced tissue cholesterol and total sterol levels, and 30- to 40-fold elevated concentrations of 7-dehydrocholesterol. Newborn homozygotes have difficulty breathing, do not suckle, and die soon after birth with immature lungs, enlarged bladder, and, frequently, cleft palate. These Dhcr7Ex8 mutant mice may be useful in studying Smith-Lemli-Opitz/RSH Syndrome (SLOS; a birth-defect mental-retardation syndrome) or other metabolic disorders involved with cholesterol biosynthesis.
A targeting vector containing a neomycin resistance gene was used to disrupt exon 8. The construct was electroporated into 129P2/OlaHsd derived E14TG2a embryonic stem (ES) cells. Correctly targeted ES cells were injected into C57BL/6 blastocysts. The mice were then bred to mice carrying the Apoetm1Unc allele (on a C57BL/6J congenic background), and then backcrossed to C57BL/6 for 8 generations prior to arriving at The Jackson Laboratory. Upon arrival, mice were bred to C57BL/6J to remove the Apoetm1Unc allele. These mice carry only the Dhcr7Ex8 mutant allele (also called Dhcr7tm1Gst).
|Allele Name||targeted mutation 1, G S Tint|
|Allele Type||Targeted (Null/Knockout, Humanized sequence)|
|Allele Synonym(s)||Dhcr7-; Dhr7delEx8|
|Gene Symbol and Name||Dhcr7, 7-dehydrocholesterol reductase|
|Strain of Origin||129P2/OlaHsd|
|Molecular Note||A mutation commonly found in human Smith-Lemli-Opitz/RSH syndrome (SLOS) was mimicked in mouse by replacement of exon 8 and the flanking regions with a PGK-neo cassette in the reverse orientation. The mutation results in deletion of 1/3 of the protein from amino acids 318-471. RT-PCR analysis of liver mRNA from homozygous mutant animals did not amplify a product using primers to the 3' end of the gene. Western blot analysis using antibodies recognizing residues 454-467 of the human protein did not detect protein product in liver proteins from homozygous mutants.|
|Mutations Made By|| |
Hongwei Wu, Medical College of Wisconsin
When maintaining a live colony, heterozygous mice are bred to wildtype siblings or to C57BL/6J inbred mice. Homozygotes have abnormalities leading to perinatal death.
When using the B6.129P2(Cg)-Dhcr7tm1Gst/J mouse strain in a publication, please cite the originating article(s) and include JAX stock #007453 in your Materials and Methods section.