OK COBRE: GENETICS OF B LYMPHOCYTE SIGNALING IN LUPUS

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Systemic lupus erythematosus (SLE) is a complex, multigenic autoimmune disease with diverse clinical symptoms. The search for the genes associated with the disease has utilized numerous complementary approachs; however, we still do not have a complete understanding of the biology behind how SLE-associated candidate genes actually cause the human disease. The complexity of the organism, the immune system and the environmental influences cloud our ability to focus on the molecular details encoded in the genome that affect the biological structures and functions in proteins important to the development of disease. B cells are now recognized as central players in the development of SLE. B cell activation is required for development of autoantibodies, which are key to the development of SLE associated pathology. We suspect genetic polymorphisms that affect the gene expression or function of proteins critical in controlling B cell signaling resulting from B cell surface receptor engagement are responsible for altered B cell responses observed in lupus patients. Our approach to identify these genes and polymorphisms requires that we first define the boundaries of the system (B cell activation and control), the measurable effects (biomolecular phenotypes) and collect phenotypic data on the population of interest. The next step would be to analyze the combined phenotypic data from phase 1 and independently collected genetic data on ancestral informative genetic markers by Quantitative Trait Association analysis. Phase 3 is to identify genetic variants responsible for altered B cell response phenotypes and determine the biomolecular pathways and mechanisms affected. We have used EBV-transformed cell lines derived from African-American (AA) lupus patients and controls to identify how key components of the B cell signaling pathways respond to B cell receptor (BCR) cross-linking. We have confirmed that cells from lupus patients and controls also exhibit altered B cell response profiles. Intracellular calcium responses, ERK1/2 phosphorylation, and Lyn phosphorylation upon B cell specific signaling are altered in these cell lines. Gene expression between cell lines from lupus patients and controls is different and has identified a set of genes/proteins which are likely involved in causing differences in B cell responses. We are beginning to identify key molecular phenotypes that characterize a lupus B cell response. We will now focus on components of those pathways as we expand our measurement and analysis of these molecular phenotypes in additional B cell lines from AA lupus cases and controls. We are examining individual candidate genes identified in the preliminary gene expression analysis, confirming their expression, exploring possible polymorphisms, and testing these for independent genetic association with lupus. We are well positioned to describe candidate functional differences in B cell responses observed in selected subsets of lupus patients and also to build the ability to exploit the power of quantitative genetic analysis in combination with biomolecular sub-phenotypes in the B cell system.