ESTABLISHMENT OF A MODEL SYSTEM TO TEST THE IMPACT OF DNA SENSING BY AIM2 ON EPITHELIAL CELL DIFFERENTIATION

Abstract

The global incidence of Inflammatory Bowel Diseases (IBD) has been on the rise. In our lab, we investigate how intestinal inflammatory responses are regulated by the innate pattern recognition receptor, Absent in Melanoma 2 (AIM2), which acts as a cytosolic dsDNA sensor. AIM2 has previously been implicated in both IBD as well as colorectal cancer. However, while AIM2 has mainly been characterized in immune cells, AIM2 is also present in epithelial cells. Preliminary evidence from our lab has shown that Aim2-/- 3D small intestine epithelial cell organoid cultures display a marked decrease in epithelial tuft cells as evidenced by loss of an associated tuft cell marker, Dclk1. Given these results, it was important to determine the mechanism by which AIM2 may regulate the differentiation of epithelial cells. To test the hypothesis that AIM2 impacts epithelial cell differentiation through its dsDNA sensing function, we optimized a 2D small intestine organoid system, which allows for cytosolic delivery of small molecules via transfection. Utilizing this 2D system, we first confirmed that the tuft cell-inducing cytokine IL-4 induces an upregulation of the tuft cell master transcription factor, Pou2f3. In response to dsDNA, there was a marked increase in Il13ra1, which encodes for the receptor shared by IL-4 and the related cytokine IL-13. These results suggest that AIM2 may promote expression of the receptor that is essential to tuft cell differentiation. These studies reveal a new mechanism by which immune sensing may play a pivotal role in intestinal epithelial homeostasis.