Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, Michigan, United States.
Department of Medicine, University of Arizona, Tucson, Arizona, United States.
Am J Physiol Gastrointest Liver Physiol. 2023 Nov 1;325(5):G458-G470. doi: 10.1152/ajpgi.00043.2023. Epub 2023 Sep 12.
Notch signaling regulates gastrointestinal stem cell proliferation and differentiation yet Notch-regulated transcriptional effectors of gastric epithelial cell differentiation are poorly understood. Here we tested the role of the bHLH transcription factor Achaete-Scute homolog 1 (ASCL1) in gastric epithelial cell differentiation, and its regulation by Notch. Newborn null mice showed a loss of expression of markers of neurogenin-3-dependent enteroendocrine cells, with normal expression of enterochromaffin-like cells, mucous cells, chief cells, and parietal cells. In adult mice, gene expression was observed in the stomach, but not the intestine, with higher expression in antral than corpus epithelium. Lineage tracing in mice revealed single, scattered ASCL1 cells in the gastric epithelium, demonstrating expression in antral gastrin- and serotonin-producing endocrine cells. ASCL1-expressing endocrine cells persisted for several weeks posttamoxifen labeling with a half-life of approximately 2 months. Lineage tracing in mice demonstrated a similar lifespan for gastrin-producing cells, confirming that gastric endocrine cells are long-lived. Finally, treatment of ; mice with the pan-Notch inhibitor dibenzazepine increased the number of lineage-labeled cells in the gastric antrum, suggesting that Notch signaling normally inhibits expression. Notch regulation of was also demonstrated in a genetic mouse model of Notch activation, as well as Notch-manipulated antral organoid cultures, thus suggesting that ASCL1 is a key downstream Notch pathway effector promoting endocrine cell differentiation in the gastric epithelium. Although Notch signaling is known to regulate cellular differentiation in the stomach, downstream effectors are poorly described. Here we demonstrate that the bHLH transcription factor ASCL1 is expressed in endocrine cells in the stomach and is required for formation of neurogenin-3-dependent enteroendocrine cells but not enterochromaffin-like cells. We also demonstrate that expression is inhibited by Notch signaling, suggesting that ASCL1 is a Notch-regulated transcriptional effector directing enteroendocrine cell fate in the mouse stomach.
Notch 信号通路调节胃肠道干细胞的增殖和分化，但 Notch 调节胃上皮细胞分化的转录效应因子知之甚少。在这里，我们测试了 bHLH 转录因子 Achaete-Scute 同源物 1（ASCL1）在胃上皮细胞分化中的作用及其受 Notch 的调节。新生 敲除小鼠表现出神经基因 3 依赖性肠内分泌细胞标志物表达缺失，肠嗜铬样细胞、粘蛋白细胞、主细胞和壁细胞表达正常。在成年小鼠中， 基因在胃中表达，但不在肠道中表达，在胃窦上皮中的表达高于胃体上皮。在 敲除小鼠中的谱系追踪显示胃上皮中有单个、散在的 ASCL1 细胞，表明其在胃窦促胃液素和 5-羟色胺产生的内分泌细胞中表达。用他莫昔芬标记后，ASCL1 表达的内分泌细胞持续存在数周，半衰期约为 2 个月。在 敲除小鼠中的谱系追踪显示促胃液素产生细胞具有相似的寿命，证实胃内分泌细胞是长寿的。最后，用 pan-Notch 抑制剂地苯扎嗪处理 敲除小鼠增加了胃窦中谱系标记细胞的数量，表明 Notch 信号通常抑制 的表达。在 Notch 激活的遗传小鼠模型以及 Notch 处理的胃窦类器官培养物中也证实了 Notch 对 的调节，因此表明 ASCL1 是 Notch 通路促进胃上皮内分泌细胞分化的关键下游效应因子。虽然 Notch 信号通路已知可调节胃中的细胞分化，但下游效应因子描述甚少。在这里，我们证明 bHLH 转录因子 ASCL1 在胃内分泌细胞中表达，是神经基因 3 依赖性肠内分泌细胞形成所必需的，但不是肠嗜铬样细胞。我们还证明， 表达受 Notch 信号抑制，表明 ASCL1 是 Notch 调节的转录效应因子，指导小鼠胃中肠内分泌细胞命运。
