PTGER4 and inflammatory bowel disease: An GWAS for inflammatory bowel disease (IBD) has identified susceptibility genes that are associated with intestinal barrier function, which included genes involved in mucus and glycoprotein regulation (ECM1, MUC3A and MUC19), membrane receptor kinase (ERRFI1), membrane transport (ITLN1 and VDR), tight junction regulation (PTPN2), epithelial restitution (PTGER4), cell polarity (PARD3), cell adhesion (CDH1 and LAMB1), tight junction assembly (GNA12, MAGI2, MYO9B and CDH1) and epithelial differentiation (HNF4A) (66).