Forward Genetic Analysis of the Toll-Like Receptor Response in Wild-Derived Mice.
Abstract: Although a
robust innate immune response is crucial to prevent fulminant pathogen dissemination,
acute inflammatory mediators produced in this process can also potently damage host
tissues. In light of these competing selective pressures, studies in evolutionarily
divergent mouse strains that have faced challenges from unique pathogens and
environments may reveal novel features of h... read moreow the inflammatory response is coordinated.
Wild-derived mouse strains have recently been captured in distinct geographical
locations and their genomes contain large intervals originating from unique Mus.
musculus subspecies. In a phenotypic screen of the TLR response in the wild-derived
strain MOLF/Ei, I observed an increase in the quantity and kinetics of IL-6 mRNA and
protein production relative to the classical strain C57BL/6J. This phenotype was
associated with a specific increase in IκB-kinase (IKK) and p38 MAPK signaling in
TLR stimulated MOLF/Ei macrophages. Linkage analysis revealed two major loci that
underlie this trait, which were named Wild-derived hyper-responsiveness 1 (Why1) and
Why2. Examination of candidate genes within Why1 identified Irak2, which has previously
been shown to sustain the late phase of NFκB activity following TLR stimulation in
classical inbred mouse strains. I provide evidence that IRAK2 is essential for the early
TLR response in MOLF/Ei, particularly for IKK and p38 activation. Analysis of Irak2
alleles from both strains revealed a mutation in the promoter of the inhibitory IRAK2
isoform, IRAK2C, which leads to an increased ratio of pro- to anti-inflammatory IRAK2
molecules in MOLF/Ei macrophages relative to those from C57BL/6J. The Why2 locus
contains Irak1bp1, a candidate gene identified through combining genetic mapping with
microarray analysis. I describe a novel anti-inflammatory role for IRAK1BP1, which
inhibits the transcription of several pro-inflammatory cytokines, while promoting IL-10
production. This effect correlates with an IRAK1BP1 dependent increase in the
concentration of p50/p50 NFκB homodimers and its association with the cytoplasmic
precursor of p50 and IκB-like protein p105. These findings reveal novel functional
roles for IRAK2 and IRAK1BP1 in an evolutionarily divergent genetic background and
demonstrate that comparison of the inflammatory response in naturally occurring mouse
strains is a viable strategy to extend our understanding of innate immune
Thesis (Ph.D.)--Tufts University, 2011.
Submitted to the Dept. of Immunology.
Advisor: Alexander Poltorak.
Committee: Naomi Rosenberg, Henry Wortis, Thereza Imanishi-Kari, and Katherine Fitzgerald.
Keyword: Immunology.read less