IL-22 promotes formation of MUC17 glycocalyx barrier in postnatal small intestine during weaning. Layunta et al.
The intestine is under constant exposure to chemicals, antigens and microorganisms from the external environment. Apical aspects of absorptive epithelial cells form a brush border membrane (BBM), shaped by packed microvilli coated with a dense glycocalyx. We present evidence showing that the glycocalyx forms an epithelial barrier that prevents exogenous molecules and live bacteria from gaining access to BBM. We use a multi-omics approach to investigate function and regulation of membrane mucins exposed on the BBM during postnatal development of mouse small intestine. Muc17 is identified as a major membrane mucin in the glycocalyx that is specifically upregulated by IL-22 as part of an epithelial defense repertoire during weaning. High levels of IL-22 at time of weaning reprogram neonatal postmitotic progenitor enterocytes to differentiate into Muc17-expressing enterocytes, as found in adult intestine during homeostasis. Our findings propose a role for Muc17 in epithelial barrier function in small intestine.