Mice that are homozygous for the toll-like receptor 5 (Tlr5) knock-out have increased fat mass, increased serum triglyceride and cholesterol levels, increased blood pressure, and higher than normal production of pro-inflammatory cytokines interferon gamma and interleukin 1 beta in adipose tissue. Homozygotes offer a model of metabolic syndrome for which the hyperphagia, obesity, hyperglycemia, insulin resistance, colomegaly, and increased pro-inflammatory cytokines can be transferred from diseased homozygotes to wild-type hosts by tranplanting gut microbiota.
Dr. Richard A. Flavell, Yale University School of Medicine
The toll-like receptor gene targeted in this strain is a sensor for monomeric flagellin, a component of bacterial flagella known to be a virulence factor. These mice have been used to investigate the mechanism of flagellin detection and signalling in antibacterial immune responses to Salmonella typhimurium and Pseudomonas aeruginosa. The gene has been found to be essential for the recognition of bacterial flagellin both in vivo and ex vivo. Mice that are homozygous for this targeted deletion are viable and fertile. Transcripts of this gene are absent from bone marrow-derived macrophages in homozygotes.
Relative to controls, homozygotes have increased fat mass throughout the body, particularly in visceral fat, a substantial increase in serum triglyceride and cholesterol levels, increased blood pressure, and higher than normal production of pro-inflammatory cytokines interferon gamma and interleukin 1 beta in adipose tissue. Basal insulin levels and insulin production in response to a glucose challenge are significantly elevated, and the response to exogenous insulin is reduced compared with that of controls. The ability to restore blood glucose to baseline levels after administration of a bolus of glucose is impaired, and a mild elevation in blood glucose levels is found after an overnight fast. After 8 weeks on a high fat diet fasting glucose concentrations exceed 120 mg/dL, inflammatory infiltrates are found in the pancreatic islets, and hepatic steatosis is observed.
Homozygotes offer a model of metabolic syndrome for which the hyperphagia, obesity, hyperglycemia, insulin resistance, colomegaly, and increased pro-inflammatory cytokines can be transferred from diseased homozygotes to wild-type hosts by tranplanting gut microbiota. Treatment of homozygotes with broad spectrum antibiotics for 12 weeks corrects the metabolic syndrome. Hysterectomy re-derivation to upgrade the microbial flora of homozygotes results in diminished severity of colitis and a more uniform phenotype of mild inflammation and obesity, including a 20% increase in body mass at 20 weeks of age.
A targeting vector was used to replace the coding region with a loxP-flanked neomycin resistance cassette inserted in the opposite transcriptional orientation. 129S1/Sv Oca2+ Tyr+ Kitl+-derived W9.5 embryonic stem (ES) cells were used to create the mutation. Resultant male chimeric mice were mated to C57BL/6 females. The donating investigator reported that this strain was backcrossed ten times to C57BL/6/Ncr mice (see SNP note below).
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, at least 1 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, Richard Flavell|
|Allele Type||Targeted (Null/Knockout)|
|Gene Symbol and Name||Tlr5, toll-like receptor 5|
|Strain of Origin||129S1/Sv-Oca2+ Tyr+ Kitl+|
|Molecular Note||A loxP-flanked neomycin selection cassette replaced the coding exon for the gene. mRNA expression in mutant and WT BM-derived macrophages was assessed by RT-PCR. Transcripts were absent in mutant but not in WT macrophages.|
|Mutations Made By|| |
Dr. Richard Flavell, Yale University School of Medicine
When maintained as a live colony, homozygotes may be bred together.
When using the TLR5 KO mouse strain in a publication, please cite the originating article(s) and include JAX stock #008377 in your Materials and Methods section.
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