Systemic lupus erythematosus (SLE) is a complex autoimmune disease with a substantial genetic component. Recent genome-wide association studies (GWAS) have identified SLE associated loci, including IKZF1 and IKZF2, encoded for ikaros and helios proteins, respectively. These proteins play important roles in regulation of differentiation of immune cells important in SLE development and drugs which regulate these protein levels are used to treat refractory cutaneous lupus and nephritis making a strong case for the importance of these genes in SLE. Our recent ImmunoChip-based association study in Asians firmly established IKZF1-SLE association and detected additional independent variants (10-24 In Aim 1, we will localize additional SLE-predisposing variants from IKZF1-2 by performing comprehensive trans-ethnic mapping across four ethnically diverse populations (N>20,000 from Asian, African-American, European-American, and Hispanic descent). Promising variants, especially imputed and low frequency variants, will be validated by confirmatory genotyping. We will also correlate genetic and clinical heterogeneity using clinical sub-phenotypes and autoantibody profiles.
In Aim 2, we will use cutting-edge approaches to directly identify functional variants in the enhancers of IKZF1-2 important for regulating expression using a novel allele-specific reporter system which works in the native chromatin context and in relevant cell types. This enables direct experimental validation of the most important variants in a human model cell system. Data generated will provide answers about SLE disease mechanisms influenced by IKZF1-2 variants, and the understanding of function of molecular variants on regulation of this pathway may enable precision application of existing treatments targeting this pathway and elucidate of new targets without the serious adverse events and limitations of these current thalidomide family-based therapies.

Public Health Relevance

Lupus is a chronic, inflammatory, autoimmune disease with profound associated morbidity and early mortality that disproportionally affects women and certain ethnic populations. Lupus has a substantial genetic component, with members of the Ikaros family of proteins believed to contribute to the disease pathogenesis. This project will identify and map the most likely SLE-predisposing variants within two of these genes, IKZF1 and IKZF2, and will determine their functional roles and the molecular mechanisms that contribute to SLE pathogenesis across multiple ethnicities, including minorities.

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
Research Project (R01)
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Arthritis, Connective Tissue and Skin Study Section (ACTS)
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Johnson, David R
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Oklahoma Medical Research Foundation
Oklahoma City
United States
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