Members of the NR4A subfamily of nuclear receptors have complex, overlapping roles during hematopoietic cell development and also function as tumor suppressors of hematologic malignancies. We previously identified NR4A1 and NR4A3 (NR4A1/3) as functionally redundant suppressors of acute myeloid leukemia (AML) development. However, their role in hematopoietic stem cell (HSC) homeostasis remains to be disclosed. Using a conditional Nr4a1/Nr4a3 knockout mouse (CDKO), we show that codepletion of NR4A1/3 promotes acute changes in HSC homeostasis including loss of HSC quiescence, accumulation of oxidative stress, and DNA damage while maintaining stem cell regenerative and differentiation capacity. Molecular profiling of CDKO HSCs revealed widespread upregulation of genetic programs governing cell cycle and inflammation and an aberrant activation of the interferon and NF-κB signaling pathways in the absence of stimuli. Mechanistically, we demonstrate that NR4A1/3 restrict HSC proliferation in part through activation of a C/EBPα-driven antiproliferative network by directly binding to a hematopoietic-specific Cebpa enhancer and activating Cebpa transcription. In addition, NR4A1/3 occupy the regulatory regions of NF-κB-regulated inflammatory cytokines, antagonizing the activation of NF-κB signaling. Taken together, our results reveal a novel coordinate control of HSC quiescence by NR4A1/3 through direct activation of C/EBPα and suppression of activation of NF-κB-driven proliferative inflammatory responses.

中文翻译：

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NR4A1 和 NR4A3 通过相互调节 C/EBPα 和炎症信号来限制 HSC 增殖

NR4A 核受体亚家族的成员在造血细胞发育过程中具有复杂、重叠的作用，并且还可以作为血液系统恶性肿瘤的肿瘤抑制因子。我们之前将 NR4A1 和 NR4A3 (NR4A1/3) 鉴定为急性髓系白血病 (AML) 发展的功能冗余抑制因子。然而，它们在造血干细胞 (HSC) 稳态中的作用仍有待披露。使用条件性 Nr4a1/Nr4a3 基因敲除小鼠 (CDKO)，我们表明 NR4A1/3 的共缺失促进 HSC 稳态的急性变化，包括 HSC 静止状态的丧失、氧化应激的积累和 DNA 损伤，同时保持干细胞的再生和分化能力。CDKO HSCs 的分子分析揭示了控制细胞周期和炎症的遗传程序的广泛上调，以及在没有刺激的情况下干扰素和 NF-κB 信号通路的异常激活。从机制上讲，我们证明 NR4A1/3 通过直接结合造血特异性 Cebpa 增强子并激活 Cebpa 转录激活 C/EBPα 驱动的抗增殖网络来部分限制 HSC 增殖。此外，NR4A1/3 占据 NF-κB 调节的炎性细胞因子的调节区域，拮抗 NF-κB 信号的激活。总之，我们的结果揭示了 NR4A1/3 通过直接激活 C/EBPα 和抑制 NF-κB 驱动的增殖性炎症反应的激活对 HSC 静止的新协调控制。