An insertion mutation in the Apoe gene associated with spontaneous hyperlipidemia in mice

INTRODUCTION: Spontaneously hyperlipidemic (SHL) mice, a mouse strain derived from an inbred strain of Japanese wild (original)-type mice (KOR; Mus musculus molossinus), show high plasma cholesterol concentrations with disruption of the apolipoprotein E (Apoe) gene. However, the details of the Apoe gene of SHL mice have yet to be described. MATERIAL AND METHODS: The DNA sequence of the Apoe gene of SHL mice was compared to that of control KOR mice in genomic DNA and cDNA analyses. RESULTS: In the DNA analysis, a 4700-bp fragment was found to be inserted into exon 4 of the Apoe gene of SHL mice. The insertion contained two 365-bp repeats at each terminal and was flanked by a 6-bp target duplication at each side. The inserted fragment produced a frameshift of an early stop codon, resulting in a protein product that consisted of 87 amino acids in SHL mice compared to 311 amino acids in control KOR mice. CONCLUSIONS: These findings provide useful information about the molecular basis of SHL mice and related lipid disorders.