Signal Transduction Laboratory, National Institute of Environmental Health Sciences/NIH, Durham, North Carolina, USA.
In Vivo Animal Core, Unit for Laboratory Animal Medicine, University of Michigan, Ann Arbor, Michigan, USA.
FASEB J. 2023 Aug;37(8):e23100. doi: 10.1096/fj.202300757R.
Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a cytokine that stimulates the proliferation and differentiation of granulocyte and macrophage precursors. The mouse gene-encoding GM-CSF, Csf2, is regulated at both transcriptional and post-transcriptional levels. An adenine-uridine-rich element (ARE) within the 3'-untranslated region of Csf2 mRNA was shown in cell transfection studies to confer instability on this transcript. To explore the physiological importance of this element in an intact animal, we generated mice with a knock-in deletion of the 75-nucleotide ARE. Mice heterozygous for this ARE deletion developed severe respiratory distress and death within about 12 weeks of age. There was dense infiltration of lung alveolar spaces by crystal-containing macrophages. Increased stability of Csf2 mRNA was confirmed in bone marrow-derived macrophages, and elevated GM-CSF levels were observed in serum and lung. These mice did not exhibit notable abnormalities in blood or bone marrow, and transplantation of bone marrow from mutant mice into lethally irradiated WT mice did not confer the pulmonary phenotype. Mice with a conditional deletion of the ARE restricted to lung type II alveolar cells exhibited an essentially identical lethal lung phenotype at the same ages as the mice with the whole-body deletion. In contrast, mice with the same conditional ARE deletion in myeloid cells, including macrophages, exhibited lesser degrees of macrophage infiltration into alveolar spaces much later in life, at approximately 9 months of age. Post-transcriptional Csf2 mRNA stability regulation in pulmonary alveolar epithelial cells appears to be essential for normal physiological GM-CSF secretion and pulmonary macrophage homeostasis.
粒细胞-巨噬细胞集落刺激因子（GM-CSF）是一种细胞因子，可刺激粒细胞和巨噬细胞前体的增殖和分化。编码 GM-CSF 的小鼠基因 Csf2 在转录和转录后水平受到调节。在细胞转染研究中，Csf2 mRNA 的 3'-非翻译区中的一个腺嘌呤-尿嘧啶丰富元件（ARE）被证明可使该转录本不稳定。为了在完整动物中探索该元件的生理重要性，我们生成了 Csf2 ARE 缺失敲入小鼠。这些 ARE 缺失杂合子小鼠在大约 12 周龄内出现严重的呼吸窘迫和死亡。肺泡空间内有富含晶体的巨噬细胞密集浸润。骨髓来源的巨噬细胞中 Csf2 mRNA 的稳定性增加得到了证实，并且血清和肺中观察到 GM-CSF 水平升高。这些小鼠在血液或骨髓中没有表现出明显异常，并且将突变小鼠的骨髓移植到致死性辐射 WT 小鼠中并没有赋予肺部表型。在肺 II 型肺泡细胞中受限的 ARE 条件性缺失的小鼠在与全身缺失的小鼠相同的年龄时表现出几乎相同的致命肺部表型。相比之下，具有相同条件性 ARE 缺失的骨髓细胞（包括巨噬细胞）中的小鼠在生命后期（约 9 个月龄）才表现出更严重的巨噬细胞浸润到肺泡空间的程度。肺肺泡上皮细胞中 Cs2 mRNA 的转录后稳定性调节似乎对于正常生理 GM-CSF 分泌和肺巨噬细胞稳态至关重要。
