Development of Human Stem Cell-Based Model to Study Lupus Risk Alleles
Abstract
Systemic lupus erythematosus (SLE or lupus) is a chronic autoimmune disease that affects almost any organ, including life-threatening impacts on the kidney and heart. Lupus afflicts 2.5 million Americans and 6 million people worldwide and is nine times more common in women than men. Although it has long been appreciated that genetic and environmental factors are involved in SLE development, only recently has the technology become sufficiently robust to pinpoint determinants that predispose individuals to lupus. Genetic association studies have identified variations (called risk variants or risk factors) between healthy individuals and SLE patients in many genes that are important for various immune cell functions. However, how these genetic risk factors may impact gene expression and function in a specific immune cell is currently unknown. It is also not clear which of the several risk factors identified for each gene truly contributes to disease development. Here, I propose to follow up on highly promising immunological pathways identified by genetic studies of lupus patients -- the STAT1 (signal transducer activator of transcription 1) and STAT4 genes that enable cells to sense and respond to changes in the state of inflammation in their environment. The STAT1 and STAT4 genes are both situated close to each other not only in human but also in mouse chromosomes. Using mouse models of SLE, we recently uncovered a critical role of the STAT1 gene in inducing SLE autoimmune responses, including anti-self antibody production and kidney disease, and which have a marked preference for affecting female animals. The role of STAT1 and STAT4 in the pathogenesis of lupus in mouse models was also previously described. Several SLE risk variants identified are located in the third intronic region (a region of the gene that does not make protein) of the STAT4 gene. Intriguingly, the STAT4 intronic region has been shown to regulate expression of both the STAT1 and STAT4 genes. The overall goal of this proposal is to develop an in vitro system to determine the consequences of these lupus-associated STAT4 intron variants on the function of different types of immune cells. To do this, I propose introducing the STAT4 SLE risk variants into human-induced pluripotent stem cells (hiPSCs) using state-of-the-art gene-editing tools, such as the CRISPR/Cas9 system (Aim 1). We will then utilize an innovative recent technology to mature hiPSCs expressing STAT4 SLE gene variants into different immune cell types (Aim 2). This proposal will focus on understanding whether and how SLE risk factors in the regulatory region of the STAT4 gene may contribute to gene expression and function in a particular cell type. This proposal relates to the FY17 LRP focus area "understanding lupus disease mechanisms." Successful completion of this project will delineate the role and function of an individual genetic risk variant or risk factor, lupus-associated genetic variants in the STAT4 intron, in SLE development. Uncovering such mechanisms may provide a novel and specific target for treating a subset of SLE patients carrying STAT4 risk factors. For instance, if we identify that a particular risk variant contributes to disease phenotype this could then be corrected in SLE patients in the future given the rapid advancement of the CRISPR/Cas9 editing system. This system will also be significantly valuable for SLE drug screening in a cell type-specific manner.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Oct 29, 2018
- Source ID
- W81XWH1810344
Entities
People
- Ziaur Rahman
Organizations
- Penn State Milton S. Hershey Medical Center
- United States Army