Intestinal epithelial cells are polarized. They have an apical side which faces the lumen of the gut and a basolateral side facing the lamina propria. The apical and basolateral membranes have a distinct lipid and protein composition providing epithelial cells their unique function at a mucosal surface. While we have previously shown that polarity is key to regulate host/pathogen interactions in the human gut, it remains unclear how polarity is established and maintained at the molecular level. Similarly, it remains unknown whether these mechanisms are similar or distinct between the different intestinal lineages. In this research axis, we employ proteomic proximity assays and CRISPR knock-in technologies to refine our molecular understanding of cellular polarity.