The epithelial-specific ER stress sensor ERN2/IRE1β enables host-microbiota crosstalk to affect colon goblet cell development
Michael J. Grey, … , Jerrold R. Turner, Wayne I. Lencer
Michael J. Grey, … , Jerrold R. Turner, Wayne I. Lencer
Published June 21, 2022
Citation Information: J Clin Invest. 2022;132(17):e153519. https://doi.org/10.1172/JCI153519.
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Research Article Gastroenterology

The epithelial-specific ER stress sensor ERN2/IRE1β enables host-microbiota crosstalk to affect colon goblet cell development

Abstract

Epithelial cells lining mucosal surfaces of the gastrointestinal and respiratory tracts uniquely express ERN2/IRE1β, a paralogue of the most evolutionarily conserved endoplasmic reticulum stress sensor, ERN1/IRE1α. How ERN2 functions at the host-environment interface and why a second paralogue evolved remain incompletely understood. Using conventionally raised and germ-free Ern2–/– mice, we found that ERN2 was required for microbiota-induced goblet cell maturation and mucus barrier assembly in the colon. This occurred only after colonization of the alimentary tract with normal gut microflora, which induced Ern2 expression. ERN2 acted by splicing Xbp1 mRNA to expand ER function and prevent ER stress in goblet cells. Although ERN1 can also splice Xbp1 mRNA, it did not act redundantly to ERN2 in this context. By regulating assembly of the colon mucus layer, ERN2 further shaped the composition of the gut microbiota. Mice lacking Ern2 had a dysbiotic microbial community that failed to induce goblet cell development and increased susceptibility to colitis when transferred into germ-free WT mice. These results show that ERN2 evolved at mucosal surfaces to mediate crosstalk between gut microbes and the colonic epithelium required for normal homeostasis and host defense.

Authors

Michael J. Grey, Heidi De Luca, Doyle V. Ward, Irini A.M. Kreulen, Katlynn Bugda Gwilt, Sage E. Foley, Jay R. Thiagarajah, Beth A. McCormick, Jerrold R. Turner, Wayne I. Lencer

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Figure 3

ERN2-mediated Xbp1 splicing and XBP1 expand ER function and prevent ER stress for goblet cell maturation.

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ERN2-mediated Xbp1 splicing and XBP1 expand ER function and prevent ER s...
(A) Representative images of AB-stained sections of distal colon from Xbp1fl/fl;Vil-Cre– (n = 6) and Xbp1fl/fl;Vil-Cre+ (n = 12) littermates. Bar graphs show the number of AB+ cells in the upper half of crypts and the AB-stained goblet cell theca area. Symbols represent individual mice, and data are represented as mean ± SEM. Mean values were compared by unpaired t test. Scale bar: 50 μm. (B) Bar graph shows relative expression of spliced Xbp1 transcript in colon crypts from (left panel) GF-WT (n = 4) and CONV-WT mice (n = 6) and (right panel) CONV-WT (n = 9) and CONV-Ern2–/– (n = 11) mice. Symbols represent individual mice, and data are represented as mean ± SEM. Mean values were compared by unpaired t test. (C) Left panel: representative images of mouse colonoids treated with the γ-secretase inhibitor DAPT in the presence or absence of the IRE1 inhibitor 4μ8C. Scale bar: 500 μm. Center panel: differentiation status was assayed by scoring spheroid versus nonspheroid morphology. Bar graph shows the change in the percentage of colonoids with spheroid morphology relative to untreated controls for a given colonoid line within an experiment. Symbols represent independent experiments (WT, n = 5; Ern2–/–, n = 7). Mean values within genotypes were compared by 2-way ANOVA. Right panel: heatmap shows relative mRNA expression for select genes measured by qPCR from a single experiment. (D) Bar graph shows the number of AB+ cells in upper half of well-defined crypts following colonization of GF-Ern2–/– mice with a microbiota from CONV-WT donor mice in the presence or absence of TUDCA. Symbols represent the average value for an individual mouse, and data are represented as mean ± SEM (WT: GF/COLONIZED, n = 5/4; Ern2–/–: GF/COLONIZED/COLONIZED+TUDCA, n = 5/5/5). Mean values were compared by 1-way ANOVA. *P < 0.05; **P < 0.01; ***P < 0.001; ****P < 0.0001.