These L-FABP knockout mice exhibit decreased fasting serum glucose levels and reduced fatty acid binding capacity of hepatic cytosol proteins. They may be useful in applications related to the study of hepatic fatty acid uptake, oxidation and metabolism, hepatic cholesterol metabolism, glucose homeostasis and obesity.
Friedhelm Schroeder, Texas A&M University
The Fabp1 (fatty acid binding protein 1, liver) gene encodes the highly conserved cytosolic chaperone protein L-FABP, which is primarily expressed in the liver. L-FABP binds long-chain fatty acids as well as other hydrophobic ligands and has a role in hepatic lipid binding and metabolism.
Mice that are homozygous for the targeted mutation are viable and fertile. No gene product (mRNA or protein) is detected by RT-PCR or Western blot analysis of liver tissue.
Although hepatic sterol carrier protein-2 (SCP-2) levels are increased by 1.4 fold in homozygotes, the hepatic level of SCP-2 precursor protein, SCP-x, is reduced by 4 fold. Homozygotes display decreased fasting serum glucose levels, and reduced fatty acid binding capacity of hepatic cytosol proteins. Female homozygotes accumulate hepatic total cholesterol. Male homozygotes exhibit reduced hepatic triacylglycerol levels. Cultured primary hepatocytes from livers of homozygous animals exhibit reduced hepatic uptake and oxidation of dietary long chain fatty acids (palmitic acid). When fed a high fat diet for 12 weeks, female mutant mice gain weight more rapidly than female wildtype controls and male homozygotes. Fat tissue mass in female homozygotes is increased by 4.5 fold, and in male homozygotes by 3.4 to 3.7 fold, compared to wildtype controls. On a chow diet, homozgyotes exhibit decreased liver weight, with male homozygotes exhibiting a lowered ratio of liver weight to body weight, than wildtype controls. On a high fat diet, liver weight is further decreased in homozygotes and both male and female homozygotes exhibit lowered ratio of liver weight to body weight. Serum beta-hydroxybutyrate levels are decreased in homozygotes, indicating decreased fatty acid oxidation.
A targeting vector designed by Drs. Friedhelm Schroeder and Bert Binas (Texas A&M University) containing NEO cassette replaced the entire coding region of the gene. The construct was electroporated into 129P2/OlaHsd-Hprtb-m3 derived HM-1 embryonic stem (ES) cells. Correctly targeted ES cells were injected into C57BL/6 blastocysts. The resulting chimeric animals were bred to C57BL/6 to achieve germline transmission. Heterozygotes were crossed to generate homozygotes. The donating investigator reports that mice were then backcrossed to C57BL/6N for 11 generations(see SNP note below). Upon arrival at The Jackson Laboratory, the mice were crossed to C57BL/6NJ (Stock No. 005304) at least once to establish the colony.
A 32 SNP (single nucleotide polymorphism) panel analysis, with 27 markers covering all 19 chromosomes and the X chromosome, as well as 5 markers that distinguish between the C57BL/6J and C57BL/6N substrains, was performed on the rederived living colony at The Jackson Laboratory Repository. While the 27 markers throughout the genome suggested a C57BL/6 genetic background, 4 of 5 markers that determine C57BL/6J from C57BL/6N were found to be segregating. These data suggest the mice sent to The Jackson Laboratory Repository were on a mixed C57BL/6J ; C57BL/6N genetic background.
|Allele Name||targeted mutation 1, Bert Binas|
|Allele Type||Targeted (Null/Knockout)|
|Allele Synonym(s)||L-FABP-; LFABP-|
|Gene Symbol and Name||Fabp1, fatty acid binding protein 1, liver|
|Strain of Origin||129P2/OlaHsd-Hprtb-m3|
|Molecular Note||The entire coding region of the gene was replaced by a neomycin resistance marker and homologous recombination was confirmed by PCR. Absence of gene transcripts was determined by RT-PCR while absence of gene product was established by Western blot.|
When maintaining a live colony, these mice can be bred as homozygotes.
When using the L-FABP knock-out mouse strain in a publication, please cite the originating article(s) and include JAX stock #022873 in your Materials and Methods section.