IL-22 promotes formation of MUC17 glycocalyx barrier in postnatal small intestine during weaning

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 used a multi-omics approach to investigate function and regulation of membrane mucins exposed on the BBM during postnatal development of the mouse small intestine. Muc17 was identified as a major membrane mucin in the glycocalyx that was specifically upregulated by IL-22 as part of an epithelial defense repertoire during weaning. High levels of IL-22 at time of weaning reprogrammed 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. Overall design: This experiment contains 4 biological groups, in 3-4 biological replicates. Samples were whole ileal tissues from mice at postnatal day 14 and 24, and mice treated with recombinant mouse Il22 or PBS via intraperitoneal injection at postnatal days 14 and 15, and sacrificed at postnatal day 16. Ileum samples for mRNA analysis were collected in RNAlater and kept at -80°C until RNA extraction. Total RNA was isolated using RNeasy Plus Mini Kit and DNase Max Kit, followed by storage at -80°C. The quality of isolated RNA was determined using a Bioanalyzer with RIN values greater than 8. cDNA libraries were prepared using the TruSeq Stranded Total RNA Sample Preparation kit with Ribo Zero Gold (Rev. E; Illumina) according to manufacturer´s protocol. Each sample has multiple raw fastq files, corresponding to different sequencing lanes (e.g., L001, L002, etc) and different reads (e.g., R1, R2).