Intestinal epithelial Casd1 influences mucus sialic acid O-acetylation and tissue damage susceptibility toward large-intestinal mucosal insults.

Jafaripour, S.; Melvin, M.; Turluk, M.; Howard, E.; Fancy, N.; Zhang, H.; Irungu, J. D. W.; Wasik, B. R.; Chou, D. C.; Bigiremana, B.; N, N.; Ma, C.; Liang, Q.; Kazemian, N.; Pakpour, S.; Parrish, C. R.; Vallance, B. A.; Zandberg, W. F.; Bergstrom, K. S. B.

doi:10.64898/2026.02.07.702670

bioRxiv · 10.64898/2026.02.07.702670

Intestinal epithelial Casd1 influences mucus sialic acid O-acetylation and tissue damage susceptibility toward large-intestinal mucosal insults.

Jafaripour, S.·Melvin, M.·Turluk, M.·Howard, E.·Fancy, N.·Zhang, H.·Irungu, J. D. W.·Wasik, B. R.·Chou, D. C.·Bigiremana, B.·N, N.·Ma, C.·Liang, Q.·Kazemian, N.·Pakpour, S.·Parrish, C. R.·Vallance, B. A.·Zandberg, W. F.·Bergstrom, K. S. B.

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Abstract

The intestinal mucus network, primarily composed of O-glycosylated MUC2 mucin polymers, is essential for protecting the gastrointestinal tract from microbial threats. Sialic acid (Sia), a terminal monosaccharide on complex O-glycans, plays a key role in maintaining mucus integrity and is frequently modified by Casd1-dependent O-acetylation (OAc). Despite its prevalence, the biological significance of sialic acid OAc (OAc-Sia) modifications in human and murine mucus remains unclear. We hypothesized that OAc-Sia variants on mucus interact with the microbiota and are required for optimal mucus barrier function and host-microbe homeostasis in the colon. To test this, we profiled OAc-Sia on human and mouse MUC2 in situ using viral-derived probes with bacterial FISH and confocal microscopy; generated intestinal epithelial cell (IEC)-specific Casd1 null mice (IEC Casd1-/-); performed sialylomic and O-glycomic HPLC-MS analyses; assessed microbial communities by 16S rRNA sequencing with quantitative microbial profiling (QMP); and evaluated disease susceptibility using DSS colitis and Citrobacter rodentium infection models. Results revealed that both human and murine mucins are extensively O-acetylated and interact with the microbiota, suggesting biological relevance. IEC Casd1-/- mice were viable and displayed a complete loss of mucin OAc-Sia, indicating Casd1 is the sole contributor to OAc-status. Unexpectedly, mucus function was intact in IEC Casd1-/- mice, with no difference in structure or quality vs. WT co-housed littermates.16S rRNA analysis showed a modest but significant sex-specific reduction of microbial loads in male IEC Casd1-/-mice, and a clear trend toward reduced Turicibacter spp. vs. WT mice in both male and females, without impacting overall short-chain fatty acid (SCFA) production. DSS treatment led to more severe and extensive tissue damage in IEC Casd1-/- mice. C. rodentium infection led to increased damage in the cecum and distal colon of IEC Casd1-/- mice without affecting pathogen load, suggesting that OAc-Sia status has a role in tolerance defense. These findings establish intestinal epithelial Sia O-acetylation as a component dispensable for mucus and host-microbe homeostasis at baseline, but important in limiting damage to mucosal inflammatory insults.

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Jafaripour, S., Melvin, M., Turluk, M., Howard, E., Fancy, N., Zhang, H., Irungu, J. D. W., Wasik, B. R., Chou, D. C., Bigiremana, B., N, N., Ma, C., Liang, Q., Kazemian, N., Pakpour, S., Parrish, C. R., Vallance, B. A., Zandberg, W. F., Bergstrom, K. S. B.. 2026-02-09. Intestinal epithelial Casd1 influences mucus sialic acid O-acetylation and tissue damage susceptibility toward large-intestinal mucosal insults.. https://doi.org/10.64898/2026.02.07.702670

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