Goblet cell-intrinsic colonic defense

Abstract

The intestine is constantly exposed to billions of commensal microbes as well as pathogens and opportunistic organisms. Protection of the epithelium depends on the mucus barrier, produced by goblet cells (GCs), which separates bacteria from host tissue while maintaining tolerance to the microbiota. Several studies have established the importance of Muc2 and the inner and outer mucus layers in maintaining intestinal homeostasis, but multiple key questions remained unresolved in our understanding of mucus associated protection to bacterial infections. It has been unclear how specialized GC subsets mature after birth, how pathogens selectively undermine these protective cells, and how environmental factors such as diet destabilize mucus integrity to permit disease. This thesis addresses these gaps by defining the developmental, functional, and pathological dynamics of distinct GC populations. We show that postnatal maturation of sentinel goblet cells (senGCs) is driven by microbial colonization, requiring Duox2 signaling to enable rapid, MAMPs-dependent mucus secretion. In parallel, noncanonical GCs contribute unique proteins to the mucus proteome reinforcing the structural and antimicrobial properties of the inner mucus layer. Building on this, we demonstrate that during Citrobacter rodentium infection, the pathogen destabilizes the inner mucus layer and potentially exploits the type III secretion system effector EspF to selectively deplete Spdef-dependent intercrypt GCs (icGCs). Loss of these cells dismantle the intercrypt mucus network, creating niches for bacterial persistence that cannot be compensated by crypt plume mucus alone. Our study further suggests that senGCs are important drivers of crypt-specific secondary defense during infection. They dynamically expand into deep crypts, sustain baseline mucus secretion, and coordinate Th17 responses. Their absence leads to accelerated GC loss, sex-specific susceptibility, and early indications of barrier compromise. Finally, we reveal that short-term exposure to a Western-style diet disrupts jejunal mucus integrity through increased Tgm2-mediated cross-linking of Muc2, preventing proper mucus expansion and enabling ectopic colonization of the small intestine by C. rodentium. Together, these findings update our understanding of the intestinal mucus barrier as a dynamic and adaptable system shaped by microbial signals, dietary factors, and contributions from specialized GC subsets. By uncovering how senGCs and icGCs preserve barrier integrity, and how pathogens and diet exploit their vulnerabilities, this work advances mechanistic understanding of how the intestinal GCs and the secreted mucus barriers preserve homeostasis and how their functional ablation creates vulnerabilities during infection.