Histone butyrylation in the mouse intestine is mediated by the microbiota and associated with regulation of gene expression.

Post-translational modifications (PTMs) on histones are a key source of regulation on chromatin through impacting cellular processes, including gene expression1. These PTMs often arise from metabolites and are thus impacted by metabolism and environmental cues2-7. One class of metabolically regulated PTMs are histone acylations, which include histone acetylation, butyrylation, crotonylation and propionylation3,8. As these PTMs can be derived from short-chain fatty acids, which are generated by the commensal microbiota in the intestinal lumen9-11, we aimed to define how microbes impact the host intestinal chromatin landscape, mainly in female mice. Here we show that in addition to acetylation, intestinal epithelial cells from the caecum and distal mouse intestine also harbour high levels of butyrylation and propionylation on lysines 9 and 27 of histone H3. We demonstrate that these acylations are regulated by the microbiota and that histone butyrylation is additionally regulated by the metabolite tributyrin. Tributyrin-regulated gene programmes are correlated with histone butyrylation, which is associated with active gene-regulatory elements and levels of gene expression. Together, our study uncovers a regulatory layer of how the microbiota and metabolites influence the intestinal epithelium through chromatin, demonstrating a physiological setting in which histone acylations are dynamically regulated and associated with gene regulation.

Altered chromatin occupancy of patient-associated H4 mutants misregulate neuronal differentiation.

Chromatin is a crucial regulator of gene expression and tightly controls development across species. Mutations in only one copy of multiple histone genes were identified in children with developmental disorders characterized by microcephaly, but their mechanistic roles in development remain unclear. Here we focus on dominant mutations affecting histone H4 lysine 91. These H4K91 mutants form aberrant nuclear puncta at specific heterochromatin regions. Mechanistically, H4K91 mutants demonstrate enhanced binding to the histone variant H3.3, and ablation of H3.3 or the H3.3-specific chaperone DAXX diminishes the mutant localization to chromatin. Our functional studies demonstrate that H4K91 mutant expression increases chromatin accessibility, alters developmental gene expression through accelerating pro-neural differentiation, and causes reduced mouse brain size in vivo, reminiscent of the microcephaly phenotypes of patients. Together, our studies unveil a distinct molecular pathogenic mechanism from other known histone mutants, where H4K91 mutants misregulate cell fate during development through abnormal genomic localization.