Genetic variation in the metal transporter ZIP8 and impact on the innate immune response in the gut

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PROJECT ABSTRACT Inflammatory bowel diseases (IBD), including Crohn’s disease (CD) and ulcerative colitis, affect 1 in 200 Americans. IBD arises through a complex interplay of genetic, immune, microbial, and environmental factors disrupting intestinal homeostasis. There is a strong call from patients to study the role of diet-derived micronutrients in intestinal homeostasis. Recent genetic studies have focused attention on ZIP8 and the role of metal transport in CD through the discovery of an association between CD and a nonsynonymous single nucleotide polymorphism (SNP, rs13107325; Ala391Thr) in SLC39A8, the gene encoding ZIP8. This SNP has also been associated with six other diseases, including obesity and schizophrenia. Further, individuals with ZIP8 A391T shared a common fecal dysbiosis independent of disease diagnosis. The function of ZIP8 in the gut is not known, but in other cell types, ZIP8-mediated zinc transport negatively regulates NF-κB signaling by complexing with IKKβ and ZIP8-mediated manganese transport balances arginine metabolism away from nitric oxide synthase to reduce oxidative stress. Our preliminary data demonstrate that ZIP8 is increased in the inflamed terminal ileum of patients with CD and ZIP8 A391T impairs negative regulation of NF-κB signaling with reduced zinc transport. We have established two model systems for the studies proposed in this application: (i) ZIP8-knockdown in human ileal enteroids and (ii) a novel knock-in mouse with ZIP8 A393T, the mouse equivalent of the human variant. We hypothesize ZIP8-mediated metal transport regulates the innate immune response in intestinal epithelial cells, and this function is changed by ZIP8 A391T to promote CD pathogenesis. The aims of this project are (1) To establish the role of ZIP8 in intestinal epithelial cells in the innate immune response, (2) To study the effect of the CD-associated genetic variation in ZIP8 (A391T) on ZIP8 function in intestinal epithelial cells, and (3) To study the effect of the CD-associated genetic variation in ZIP8 on colitis susceptibility in a novel knock-in mouse model (ZIP8 A393T). The candidate is an Assistant Professor of Medicine at the Johns Hopkins School of Medicine in the Division of Gastroenterology with research and clinical training dedicated to IBD. The goal for this applicant is to use this project to enhance her molecular biology and immunology expertise and position her to build an independent career as a physician- scientist dedicated to studying the role of micronutrients in the pathophysiology of IBD. In addition to hands-on training and didactic education, the Training Plan includes strong mentorship from a Scientific Advisory Committee with diverse expertise in epithelial biology, metal biology, NF-κB signaling, oxidative stress, host- microbiota interactions and IBD, complemented by the strong support of the Hopkins Conte Digestive Diseases Basic and Translational Research Core Center and the institution.