Finkelman, F. D. | bioRxiv Science

bioRxiv2023

Microbiota epigenetically direct tuft cell differentiation to control type 2 immunity

Allergy and anti-helminth immunity are driven by type 2 responses in mucosal tissues. Tuft cells are key regulators of type 2 immunity, however the factors that control these cells remain poorly understood. Here we find that butyrate-producing commensal bacteria decrease tuft cells in the intestine. Butyrate suppression of tuft cells required the epigenetic modifying enzyme histone deacetylase 3 (HDAC3), suggesting that HDAC3 may promote tuft cell-dependent immunity. Consistent with this, epithelial-intrinsic HDAC3 actively regulated tuft cell expansion in vivo and was required to induce type 2 immune responses during helminth infection. Interestingly, butyrate epigenetically restricted stem cell differentiation into tuft cells, and inhibition of HDAC3 in adult mice and human intestinal organoids was sufficient to block tuft cell expansion. Collectively, these data reveal an epigenetic pathway in stem cells that directs tuft cell differentiation, and highlight a new level of regulation through which commensal bacteria calibrate intestinal immunity.

immunology↗

bioRxiv2022

The GC box at the proximal enhancer of the Hdc gene is critical for Hdc gene transcription and histamine-mediated anaphylaxis

Background: Histamine is a critical mediator of anaphylaxis, a neurotransmitter, and a regulator of gastric acid secretion. Histidine decarboxylase is a rate-limiting enzyme for histamine synthesis. However, in vivo regulation of Hdc, the gene that encodes histidine decarboxylase is poorly understood. Objective: We sought to investigate how enhancers regulate Hdc gene transcription and histamine synthesis in resting conditions and in a mouse model of anaphylaxis. Methods: H3K27 acetylation histone modification and chromatin accessibility were used to identify candidate enhancers; The enhancer activity of candidate enhancers was measured in a reporter gene assay; and the function enhancers were validated using CRISPR deletion. Results: Deletion of the GC box, which binds to zinc finger transcription factors, in the proximal Hdc enhancer, reduced Hdc gene transcription and histamine synthesis in the mouse and human mast cell lines. Mast cells, basophils, brain cells, and stomach cells from GC box-deficient mice transcribed the Hdc gene much less than similar cells from wild-type mice and Hdc GC box-deficient mice failed to develop anaphylaxis. Conclusion: Our results demonstrate that the HDC GC box within the proximal enhancer in the mouse and human HDC gene is essential for Hdc gene transcription, histamine synthesis, and histamine-mediated anaphylaxis in vitro and in vivo. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=104 SRC="FIGDIR/small/495950v3_ufig1.gif" ALT="Figure 1"> View larger version (40K): org.highwire.dtl.DTLVardef@106f99org.highwire.dtl.DTLVardef@10ec8b8org.highwire.dtl.DTLVardef@19bb1ceorg.highwire.dtl.DTLVardef@b663cd_HPS_FORMAT_FIGEXP M_FIG C_FIG Key messages: O_LIThe HDC GC box within the proximal enhancer of the mouse and human HDC gene is essential for Hdc gene transcription and histamine synthesis in mouse and human mast cells. C_LIO_LIThe mouse Hdc GC box is required for histamine-mediated anaphylaxis in vivo. C_LI Capsule summary Our results demonstrate that the Hdc GC box within the proximal enhancer of the mouse and human HDC gene is essential for Hdc gene transcription and histamine synthesis in mast cells. The mouse Hdc GC box is required for histamine-mediated anaphylaxis in the mouse model of anaphylaxis.

immunology↗