International Mammalian Genome Society

logo18th International Mouse Genome Conference

17-22 October 2004, Seattle, USA


POSTER 88 - A SCREEN FOR NOVEL GENES INVOLVED IN TLR SIGNALING

Jiang ZF, Du X, Shamel L, Beutler B

The Scripps Research Institute, La Jolla, United States

Toll-like receptors (TLRs) play essential roles in inflammation and innate immunity. Individual TLRs respond to specific molecules of microbial origin. TLR4 has been identified as the sensor for lipopolysaccharide (LPS), a molecular component of Gram-negative bacteria. TLR2 responds to molecules derived from mycobacteria, yeast, and Gram-positive bacteria. TLR5 and TLR9 recognize bacterial flagellins, and unmethylated DNA bearing CpG motifs, while TLR3 and TLR7 recognize viral double-stranded RNA (dsRNA) and single-stranded RNA (ssRNA), respectively.  While many of the molecules involved in TLR-mediated signaling have been identified, others remain obscure, and numerous questions surround the sensing mechanism itself.  ENU mutagenesis has been used to identify novel genes in the process by screening for ENU-caused germline mutants that are defective to different ligands. Previous work in our lab has shown that LPS2/TRIF is required for mediating the signaling through TLR3 and TLR4, and that CD36 is involved in TLR2/6 mediated LTA sensing.  We now report additional mutations (Insouciant, Heedless, and Unmindful) that affect TLR sensing.  Insouciant macrophages show decreased responses to peptidoglycan (PGN), suggesting the mutated gene is involved in responses to one or more molecular components of commercial peptidoglycan preparations.  Heedless displays reduced response to both LPS and the tri-acylated bacterial lipopeptide PAM3CSK4, suggesting that an unknown protein might be involved in TLR4 and TLR2/1 (but not TLR2/6) sensing. Unmindful shows no response to Poly I:C and PAM3CSK4, as well as a reduced response to CpG DNA.  Each mutation is being expanded for positional identification.

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