Early-life microbiota skews long-term gene expression and chromatin states of bone marrow hematopoietic precursors.

Early life is a critical window during which the gut microbiota sculpts immunity and long-term susceptibility to allergic disease. Using neonatal antibiotic administration and bone marrow transplantation assays, we show that depletion of short-chain fatty acid (SCFA)-producing bacteria alters gene expression in hematopoietic stem and progenitor cells (HSPCs) and imprints a persistent, transplantable atopic immune phenotype. Bone marrow transplants from exposed mice generate recipients with elevated serum immunoglobulin E (IgE), downstream increased IgE bound to basophils, and exacerbated allergic lung inflammation following papain challenge. Depletion of SCFA-producing bacteria also impairs recovery from chemotherapy-induced myelosuppression and increases DNA damage in long-term HSPCs in an antibiotic-specific manner. Histone 3 lysine 27 (H3K27) chromatin immunoprecipitation sequencing (ChIP-seq) analyses further reveal differential histone acetylation in HSPCs, consistent with an SCFA-mediated epigenetic regulatory mechanism. Collectively, these findings establish a link between gut microbiota composition, hematopoiesis, and long-term immune function, offering a mechanistic explanation for microbiota-driven susceptibility to atopic disease and hematopoietic dysfunction.