The phenomenon of sepsis can be separated what might be called "sensing" and "post-sensing" phases. The sensing phase entails the innate immune perception of bacteria, and occurs largely via Toll-like receptors, which trigger a complex cytokine response. The post-sensing phase encompasses the reaction of tissues, organs, and organ systems to the cytokine response. The post-sensing phase is largely terra incognita. Much ofthe variability in clinical course and clinical outcome between individuals with comparable infections may be explained by differences manifested at this level. Some of the differences are agedependent. Others are clearly genetic. The purpose of the current proposal is to identify mutations that render mice highly susceptible to LPS through effects downstream of the initial innate immune response. We also hope to understand precisely how these mutations operate. A genetic approach will be used in our work. Random germline mutagenesis will be performed in the C57BL/6J strain using N-ethyl-N-nitrosourea (ENU). Mutations will be brought to homozygosity, and male mice will be screened for lethality or severe illness when injected with a normally harmless quantity of LPS (10-20 ug). When lethality or severe illness is encountered, sperm from the affected individual will be used to preserve the germline. We will then perform intracytoplasmic sperm injection (ICSI) using oocytes from the closely related C57BL/10J strain, for which we have established an informative mapping panel. Mapping will be accomplished using bulk segregation analysis: a technique we have also recently developed for the C57BL/6J x C57BL/10J strain combination. DNA from the index mouse will be sequenced to identify all candidate mutations. The mutation implicated in this process will be confirmed by BAC transgene rescue or gene trap complementation studies. At the same time, a suppression screen will be used to clarify the mode of action of one mutation that causes hypersensitivity to LPS, called MayDay. This mutation has been found to be suppressed by Bourgeoisie, an ENU mutation detected during the first cycle of funding. Bourgeoisie will be positionally cloned, and other mutations like it will be found, using a positional cloning strategy similar to the one just described. Our work will help to explain why some individuals with bacteremia are likely to develop sepsis while others are not. Moreover, by disclosing points of host vulnerability during infection, it may suggest pharmacotherapeutic interventions helpful to all patients with sepsis.
While many people experience bacteremia (bacteria in the blood) at some point during their lives, and exhibit a normal innate immune response, some develop overwhelming sepsis~a fall in blood pressure and severe damage to internal organs-while others do not. This research seeks to identify the genetic differences that explain variability in human responses to infection, particulariy infection with Gram-negative bacteria. This work may lead to an appreciation of who is at risk, and may also suggest therapies for sepsis in all people.
|Beutler, Bruce (2016) Innate immunity and the new forward genetics. Best Pract Res Clin Haematol 29:379-387|
|Wang, Tao; Zhan, Xiaowei; Bu, Chun-Hui et al. (2015) Real-time resolution of point mutations that cause phenovariance in mice. Proc Natl Acad Sci U S A 112:E440-9|
|Moresco, Eva Marie Y; Li, Xiaohong; Beutler, Bruce (2013) Going forward with genetics: recent technological advances and forward genetics in mice. Am J Pathol 182:1462-73|
|Siggs, Owen M; Xiao, Nengming; Wang, Ying et al. (2012) iRhom2 is required for the secretion of mouse TNFÎ±. Blood 119:5769-71|
|Arnold, Carrie N; Pirie, Elaine; Dosenovic, Pia et al. (2012) A forward genetic screen reveals roles for Nfkbid, Zeb1, and Ruvbl2 in humoral immunity. Proc Natl Acad Sci U S A 109:12286-93|
|Arnold, Carrie N; Barnes, Michael J; Berger, Michael et al. (2012) ENU-induced phenovariance in mice: inferences from 587 mutations. BMC Res Notes 5:577|
|Won, Sungyong; Eidenschenk, Celine; Arnold, Carrie N et al. (2012) Increased susceptibility to DNA virus infection in mice with a GCN2 mutation. J Virol 86:1802-8|
|Rutschmann, Sophie; Crozat, Karine; Li, Xiaohong et al. (2012) Hypopigmentation and maternal-zygotic embryonic lethality caused by a hypomorphic mbtps1 mutation in mice. G3 (Bethesda) 2:499-504|
|Brandl, Katharina; Tomisato, Wataru; Li, Xiaohong et al. (2012) Yip1 domain family, member 6 (Yipf6) mutation induces spontaneous intestinal inflammation in mice. Proc Natl Acad Sci U S A 109:12650-5|
|Siggs, Owen M; Li, Xiaohong; Xia, Yu et al. (2012) ZBTB1 is a determinant of lymphoid development. J Exp Med 209:19-27|
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