|Coordinate||66,839,254 bp (GRCm38)|
|Base Change||A ⇒ T (forward strand)|
|Gene Name||toll-like receptor 4|
|Synonym(s)||Rasl2-8, Lps, lipopolysaccharide response|
|Chromosomal Location||66,827,584-66,930,284 bp (+)|
FUNCTION: This gene belongs to the evolutionarily-conserved Toll-like receptor family, whose members are type-1 transmembrane proteins that are involved in innate immunity. Toll-like receptors are characterized by an extracellular leucine-rich repeat domain that functions in ligand recognition and an intracellular toll/interleukin-1 receptor-like domain that is crucial for signal transduction. The receptor encoded by this gene mediates the innate immune response to bacterial lipopolysaccharide, a major component of the outer membrane of Gram-negative bacteria, through synthesis of pro-inflammatory cytokines and chemokines. In addition, this protein can recognize other pathogens from Gram-negative and Gram-positive bacteria as well as viral components. Mice deficient in this gene display a number of immune response-related phenotypes including hyporesponsiveness to bacterial lipopolysaccharide and increased levels of respiratory syncytial virus compared to controls. [provided by RefSeq, Sep 2015]
PHENOTYPE: Homozygotes for spontaneous or targeted mutations are hyporesponsive to bacterial lipopolysaccharide and more susceptible to infection by gram negative bacteria. [provided by MGI curators]
|Amino Acid Change||Lysine changed to Stop codon|
|Institutional Source||Beutler Lab|
|Gene Model||predicted gene model for protein(s): [ENSMUSP00000045770] [ENSMUSP00000102988]|
AA Change: K95*
|Predicted Effect||probably null|
|Predicted Effect||probably benign|
|Alleles Listed at MGI|
|Mode of Inheritance||Autosomal Recessive|
|Last Updated||2016-12-09 10:16 AM by Katherine Timer|
|Record Created||2015-09-11 4:21 PM|
The bugsy phenotype was identified among N-ethyl-N-nitrosourea (ENU)-mutagenized G3 mice of the pedigree R3011, some of which showed reduced TNFα secretion from macrophages in response to the Toll-like receptor 4 (TLR4) ligand, lipolysaccharide (LPS) (Figure 1) and resistance to LPS-induced macrophage necroptosis (Figure 2).
|Nature of Mutation|
Whole exome HiSeq sequencing of the G1 grandsire identified 33 mutations. Both of the above phenotypes were linked by continuous variable mapping to a mutation in Tlr4: an A to T transversion at base pair 66,839,254 (v38) on chromosome 4, or base pair 11,444 in the GenBank genomic region NC_000070. The strongest association was found with a recessive model of linkage to the reduced LPS-induced macrophage necroptosis, wherein one variant homozygote departed phenotypically from nine homozygous reference mice and 16 heterozygous mice with a P value of 6.016 x 10-23 (Figure 3). A substantial semidominant effect was observed in the TLR4 signaling assay using gene-based superpedigree analysis of pedigrees R3011 and R0827.
The mutation corresponds to residue 564 in the mRNA sequence NM_021297 within exon 3 of 3 total exons.
The mutated nucleotide is indicated in red. The mutation results in substitution of lysine (K) 95 to a premature stop codon (K95*) in the TLR4 protein.
TLR4 is a type I integral membrane glycoprotein containing 835 amino acids. TLR4 has 22 predicted leucine-rich repeats (LRRs) in its ectodomain at the N-terminal half of the protein (1-3), a transmembrane domain, and a cytoplasmic Toll/IL-1R (TIR) domain (Figure 5). The bugsy mutation results in substitution of lysine 95 to a premature stop codon (K95*), which is located in LRR3.
Please see the record for lps3 for information about Tlr4.
TLR4 is the receptor for LPS (4). Stimulation of TLR4 by LPS activates two branches of signaling, one defined by early NF-κB activation (MyD88-dependent pathway, mediated by MyD88), and another distinguished by late NF-κB activation as well as interferon responsive factor (IRF)-3 activation leading to type I IFN production and costimulatory molecule upregulation (MyD88-independent pathway, mediated by Trif) (5-7). The MyD88-dependent pathway activates expression of target genes including interleukin (IL)-6, IL-1, TNF, IL-12p40 and type I interferon (IFN), cytokines required for the inflammatory response. The MyD88-independent pathway results in the production of type I IFN. The reduction in TLR4-associated responses in bugsy indicates that the mutation results in loss of TLR4 function.
bugsy(F):5'- AAATCTGCAGAGTTCCTCTCC -3'
bugsy(R):5'- GTGAGCCACATTGAGTTTCTTTAAG -3'
bugsy_seq(F):5'- TGCTCACACCATCATCACCTG -3'
bugsy_seq(R):5'- TAAGGTTATAAGCTGTCCAATAGGG -3'
2. Medzhitov, R., Preston-Hurlburt, P., and Janeway, C. A.,Jr. (1997) A Human Homologue of the Drosophila Toll Protein Signals Activation of Adaptive Immunity. Nature. 388, 394-397.
3. Bell, J. K., Mullen, G. E., Leifer, C. A., Mazzoni, A., Davies, D. R., and Segal, D. M. (2003) Leucine-Rich Repeats and Pathogen Recognition in Toll-Like Receptors. Trends Immunol. 24, 528-533.
4. Poltorak, A., He, X., Smirnova, I., Liu, M. -., Van Huffel, C., Du, X., Birdwell, D., Alejos, E., Silva, M., Galanos, C., Freudenberg, M. A., Ricciardi-Castagnoli, P., Layton, B., and Beutler, B. (1998) Defective LPS Signaling in C3H/HeJ and C57BL/10ScCr Mice: Mutations in Tlr4 gene. Science. 282, 2085-2088.
5. Kawai, T., Adachi, O., Ogawa, T., Takeda, K., and Akira, S. (1999) Unresponsiveness of MyD88-Deficient Mice to Endotoxin. Immunity. 11, 115-122.
6. Hoshino, K., Kaisho, T., Iwabe, T., Takeuchi, O., and Akira, S. (2002) Differential Involvement of IFN-Beta in Toll-Like Receptor-Stimulated Dendritic Cell Activation. Int Immunol. 14, 1225-1231.
7. Kawai, T., Takeuchi, O., Fujita, T., Inoue, J., Muhlradt, P. F., Sato, S., Hoshino, K., and Akira, S. (2001) Lipopolysaccharide Stimulates the MyD88-Independent Pathway and Results in Activation of IFN-Regulatory Factor 3 and the Expression of a Subset of Lipopolysaccharide-Inducible Genes. J Immunol. 167, 5887-5894.
|Science Writers||Anne Murray|
|Authors||Ying Wang, Hexin Shi, Zhao Zhang, Lei Sun, Doan Dao, Bruce Beutler|