Department of Immunology and Genomic Medicine, National Jewish Health, Denver, Colo.
Department of Medicine, Division of Immunology, Allergy, and Rheumatology, University of Cincinnati College of Medicine, Cincinnati, Ohio.
J Allergy Clin Immunol. 2023 Jul;152(1):195-204.e3. doi: 10.1016/j.jaci.2023.01.031. Epub 2023 Feb 18.
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.
We sought to investigate how enhancers regulate Hdc gene transcription and histamine synthesis in resting conditions and in a mouse model of anaphylaxis.
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 by CRISPR deletion.
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 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.
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.
组氨酸脱羧酶是组氨酸合成的限速酶，而组胺是过敏反应的关键介质、神经递质和胃酸分泌的调节剂。然而，组氨酸脱羧酶（Hdc）基因的体内调节机制目前尚不清楚。
本研究旨在探讨增强子在过敏反应小鼠模型和静息状态下如何调控 Hdc 基因转录和组氨酸合成。
通过 H3K27 乙酰化组蛋白修饰和染色质可及性来鉴定候选增强子。通过报告基因检测来测量候选增强子的活性，并通过 CRISPR 缺失来验证增强子的功能。
在小鼠和人类肥大细胞系中，缺失近端 Hdc 增强子中的 GC 盒（与锌指转录因子结合）可降低 Hdc 基因转录和组氨酸合成。GC 盒缺失的肥大细胞、嗜碱性粒细胞、脑细胞和胃细胞的 Hdc 基因转录水平明显低于野生型小鼠的类似细胞，并且 GC 盒缺失的 Hdc 小鼠无法发生过敏反应。
在小鼠和人类的 HDC 基因中，近端增强子内的 HDC GC 盒对于 Hdc 基因转录、组氨酸合成以及组胺介导的过敏反应是必需的。
