Weaning-Driven Gut Microbiome Shapes Intestinal Stem Cell Epigenetics to Train Immunological Memory (RNA-seq)

During weaning, the transition to solid food diversifies the gut microbiome, triggering a programmed immune response critical for long-lasting mucosal immunity. Previous work showed that the gut microbiome mediates epigenetic development in intestinal stem cells (ISCs) during suckling, but what happens during weaning is unclear. Here, using genome-wide methylation profiling revealed that weaning-driven microbiome changes shape the DNA methylome and transcriptome of murine ISCs in an IFN-g dependent manner. Specifically, we observe demethylation of enhancer elements essential for MHC class II genes, which result in a transcriptional memory that persists through differentiation into adulthood. IFN-g blockade, or low-dose penicillin to target Gram-positive bacteria, in early life impaired microbiome-mediated epigenetic control and mucosal immunity, and exacerbated colitis. Murine organoids primed with IFN-g showed rapid, amplified transcriptional responses upon secondary stimulations. These findings reveal that early-life events alter the gut microbiome and these changes reprogram ISC epigenetic memory to shape mucosal immunity.