Pou2af1 Deficiency Aggravates DSS-Induced Colitis via Impaired Germinal Center Responses and Altered Gut Microbiota

Abstract Background Bob1 plays a critical role in immune system regulation, particularly in the function of B cells. Its deficiency in the context of colitis remains underexplored. This study investigates the effects of Bob1 (Pou2af1) deficiency on colitis, particularly focusing on immune responses and gut microbiota alterations in a murine model. Methods In this study, we employed Pou2af1 knockout (KO) and wild-type (WT) mice to investigate the role of Bob1 in dextran sodium sulfate (DSS)-induced colitis. Colitis was induced by administering 2.5% DSS in drinking water for 7 days. Mice were monitored daily for weight loss, stool consistency, and rectal bleeding to calculate the disease activity index (DAI). Colon length was measured, and colon tissues were collected for histological analysis using hematoxylin and eosin (H&E) staining. Flow cytometry was performed to assess germinal center responses as well as the proportion of T helper (Th)1 and Th17 cells in the colonic lamina propria. Metagenomic sequencing was conducted on fecal samples to evaluate gut microbiota composition. Results Pou2af1-deficient mice exhibited significantly exacerbated colitis compared to WT mice. This was evidenced by greater weight loss, elevated disease activity index, reduced colon length, and more severe pathological changes. Immune analysis revealed an impaired germinal center response, diminished generation of IgA⁺ plasma cells, and decreased Th17 cells in the colonic lamina propria in Pou2af1-deficient mice. Additionally, microbiota analysis indicated dysbiosis in the Pou2af1-deficient group, with a notable decrease in Bacteroides species and an increase in pro-inflammatory microbes. Discussion The findings suggest that Pou2af1 deficiency exacerbates DSS-induced colitis by impairing immune responses, particularly the germinal center reaction, and altering gut microbiota composition. These alterations contribute to increased disease severity, highlighting the importance of Pou2af1 in maintaining intestinal immune homeostasis.