Liver-specific inactivation of the abetalipoproteinemia gene completely abrogates very low density lipoprotein/low density lipoprotein production in a viable conditional knockout mouse.

Abstract

Conventional knockout of the microsomal triglyceride transfer protein large subunit (lMTP) gene is embryonic lethal in the homozygous state in mice. We have produced a conditional lMTP knockout mouse by inserting loxP sequences flanking exons 5 and 6 by gene targeting. Homozygous floxed mice were born live with normal plasma lipids. Intravenous injection of an adenovirus harboring Cre recombinase (AdCre1) produced deletion of exons 5 and 6 and disappearance of lMTP mRNA and immunoreactive protein in a liver-specific manner. There was also disappearance of plasma apolipoprotein (apo) B-100 and marked reduction in apoB-48 levels. Wild-type mice showed no response, and heterozygous mice, an intermediate response, to AdCre1. Wild-type mice doubled their plasma cholesterol level following a high cholesterol diet. This hypercholesterolemia was abolished in AdCre1-treated lMTP-/- mice, the result of a complete absence of very low/intermediate/low density lipoproteins and a slight reduction in high density lipoprotein. Heterozygous mice showed an intermediate lipoprotein phenotype. The rate of accumulation of plasma triglyceride following Triton WR1339 treatment in lMTP-/- mice was <10% that in wild-type animals, indicating a failure of triglyceride-rich lipoprotein production. Pulse-chase experiments using hepatocytes isolated from wild-type and lMTP-/- mice revealed a failure of apoB secretion in lMTP-/- animals. Therefore, the liver-specific inactivation of the lMTP gene completely abrogates apoB-100 and very low/intermediate/low density lipoprotein production. These conditional knockout mice are a useful in vivo model for studying the role of MTP in apoB biosynthesis and the biogenesis of apoB-containing lipoproteins.

• Authors: B H Chang, W Liao, L Li, M Nakamuta, D Mack, L Chan
• Journal: The Journal of biological chemistry (J Biol Chem) Vol. 274 Issue 10 Pg. 6051-5 (Mar 05 1999) ISSN: 0021-9258 [Print] United States
• PMID: 10037685 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• Apolipoproteins B
• Carrier Proteins
• Lipoproteins, LDL
• Lipoproteins, VLDL
• microsomal triglyceride transfer protein

Topics

• Abetalipoproteinemia (genetics, metabolism)
• Animals
• Apolipoproteins B (genetics)
• Carrier Proteins (genetics)
• Disease Models, Animal
• Lipoproteins, LDL (biosynthesis, genetics)
• Lipoproteins, VLDL (biosynthesis, genetics)
• Liver (metabolism)
• Mice
• Mice, Knockout