The overarching goal of this program project is to characterize genes and genetic pathways that either enhance or suppress the development of systemic autoimmunity. This program project previously focused on characterizing the genetic basis of susceptibility to systemic autoimmunity using a collection of congenic strains to model specific stages of disease development. These studies revealed the locations and functional properties of novel genetic loci that either enhanced or suppressed the transition into autoimmune disease. We are now proposing to identify several of the specific genes and genetic pathways that either suppress or enhance the development of autoimmune disease. Project 1 (P.I. Wakeland) will identify Sles1, a powerful suppressive modifier that can completely suppress fatal disease mediated by a combination of potent autoimmune susceptibility genes. Project 2 (P.I. Mohan) will characterize the in vivo properties of two disease alleles (Ifi202, CXCR4) using a novel transgenic system that allows the induction of expression of specific genes in specific cell lineages. Project 3 (P.I. Satterthwaite) will investigate the mechanisms by which interactions between the negative regulator lyn and Btk cause the development of autoimmunity. These studies will elucidate the processes that either increase or suppress lupus development, and also define how these processes interact with each other. The program is supported by three scientific cores: 1) a mouse core that will provide a variety of novel mouse models of autoimmunity;2) a genomics core that will produce novel transgenic and gene knock-in mouse strains and perform gene expression profiling;and 3) a flow cytometry core that will support sophisticated cell lineage and sorting studies. The long term goal of the program is to identify genes and genetic pathways that become dysregulated during the development of autoimmunity and the progressive transition to severe disease. The identification and characterization of these genes and genetic pathways will provide important insights into the mechanisms that maintain immune tolerance and potentially identify new approaches for therapeutic intervention in systemic autoimmunity. PROJECT 1: Genetic Mechanisms to Suppress Autoimmunity (Wakeland, E) PROJECT 1 DESCRIPTION (provided by applicant): We propose to identify Sles1, an epistatic modifier that suppresses the development of fatal lupus in our B6-congenic model of systemic autoimmunity. In preliminary studies, we have localized this gene into a 442 Kb congenic interval on murine chromosome 17. The identification of Sles1 is an essential first step in elucidating the molecular pathways and cellular processes that underlie the capacity of this locus to suppress a potent combination of disease alleles. We have three aims:
Specific aim 1. To identify the gene or genes mediating the autoimmune suppressive phenotype of Sles1. The Sles1 442 Kb critical interval is spanned by 3 overlapping B6-derived BACs (bacterial artificial chromosomes). Suppression of autoimmunity by Sles1 is recessive to the Sles1 allele derived from B6 mice, indicating that a B6-derived BACs containing the Sles1 locus will cause B6.Sle1yaaSles1 and B6.Sle1Sles1 mice to develop autoimmunity. Our experimental strategy for the identification of Sles1 will be: 1) to localize Sles1 into an interval of <100 Kb containing ~5-10 positional candidates via the analysis of phenotypic rescue using this series of three overlapping B6-derived BACs;2) a focused genomic analysis of the positional candidates that remain in the segment identified by BAC transgenic rescue;and 3) the definitive identification of Sles1 using BAC modification strategies for in vivo identification of the causative allele.
Specific aim 2. To identify the cell lineage(s) that express Sles1 and assess the cellular interactions mediating the suppression of autoimmunity. We will initially determine whether Sles1 is expressed by hematopoietic cells by performing reciprocal bone marrow transplants between B6.Sle1 and B6.Sle1Sles1 mice. This strategy will be extended to the analysis of specific immune cell lineages if Sles1 is expressed in hematopoietic cell lineages. The goal of these studies will be to define the cell-intrinsic expression of Sles1.
Specific aim 3. To determine whether Sles1 directly suppresses the disruption of immune tolerance in immature B cells mediated by Ly108-1. We previously demonstrated that the preferential expression of the Ly108-1 isoform of the SLAM/CD2 haplotype in B6.Sle1 mice causes a breach in tolerance in the immature B cell compartment. We will determine whether Sles1 suppression of B6.Sle1 is mediated by correcting the breach in tolerance in immature B cells.
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