Genetic Dissection of Lipopolysaccharide Response

描述(申请人提供)：采用生化和遗传学相结合的方法分析了脂多糖(LPS)信号通路。然而，并不是所有参与内毒素识别的蛋白质都被识别出来。为了发现更多的内毒素反应，我们对几个近交系小鼠的内毒素反应进行了评价，并对其反应差异的遗传基础进行了探讨。其中，BALB/C株和C3H/HEN株对内毒素的反应差异显著。为进一步探讨TLR4与内毒素反应的关系，对(BALB/C×C3H/HEN)F2杂交小鼠进行了内毒素反应分析和TLR4基因分型。这些数据表明，虽然在BALB/C和C3H/HEN小鼠之间观察到了TLR4的功能多态性，但更多的基因明显参与了内毒素反应。为了定位这些基因，扩大了F2小鼠的群体，并进行了全基因组筛查，所有后代都进行了TLR4基因座的基因分型。对BALB/C小鼠80个减数分裂的遗传分析表明，BALB/C小鼠对脂多糖的低反应性与6号和17号染色体上的基因座连锁。为了进一步鉴定候选基因和提高遗传图谱的分辨率，构建了两个同源株：一个是以C3H/HEN为背景的TLR4的BALB/C等位基因，另一个是以BALB/C为背景的TLR4的BALB/C等位基因。进一步对这些菌株进行分析，以确定它们对内毒素的反应水平。两个新的基因座，命名为Lpm1和Lpm2，可能与内毒素反应有关。Lpm1和Lpm2的阐明将代表一个重要的进展，因为许多已知对复杂性状有贡献的基因可以通过这种方法识别出来。类似的策略也被用来分析F2杂交动物对肽聚糖的杂交反应。阐明小鼠抗菌反应的精确机制，无疑将有助于研究宿主对人类传染病的抵抗力。

DESCRIPTION (provided by applicant): The lipopolysaccharide (LPS) signaling pathway has been analyzed using combination of biochemical and genetic methods. However, not all of the proteins that participate in LPS recognition have been identified. In order to find more of them, several inbred strains of mice were evaluated on their LPS response and genetic basis of the differences in this response was examined. Among them, BALB/C and C3H/HeN strains differ significantly in their response to LPS. To further determine the relationship between TLR4 LPS response, (BALB/C x C3H/HeN) F2 intercross mice were analyzed on their LPS response and genotyped for TLR4 locus. These data show that although there is functional polymorphism in TLR4 observed between BALB/C and C3H/HeN mice, additional genes are clearly involved in LPS response. In order to map these genes, the panel of F2 mice was expanded and subjected to genome wide screening with all progeny genotyped for TLR4 locus. Genetic analysis of 80 meioses revealed that hyporesponse of BALB/C mice to LPS is linked to loci on chromosomes 6 and 17. To further characterize candidates and to improve resolution of genetic mapping, two congenic strains were constructed: one with BALB/C allele of TLR4 on C3H/HeN background and another - with HeN allele of TLR4 on BALB/C background. These strains were further analyzed to determine the level of their response to LPS. Two new loci, termed Lpml and Lpm2, may be assumed to contribute to the LPS response. The elucidation of Lpml and Lpm2 will represent an important advance, in that many genes that are known to contribute to complex traits can be identified by such approach. Similar strategy was employed for analysis of intercross response to peptidoglycan in F2 intercross animals. Elucidation of a precise mechanism of anti-bacterial response in a mouse model will undoubtedly contribute to the studies of host resistance to infectious diseases in humans.