Mechanisms of granulocyte homeostasis

摘要 了解粒细胞动态平衡背后的细胞和分子过程至关重要，因为 产生太少的粒细胞会增加感染的风险(中性粒细胞减少症)，而产生太多的粒细胞 粒细胞可导致严重的组织损伤和死亡(骨髓增生性疾病)。勾勒出 中性粒细胞产生的动态平衡的分子机制，我们先前描述了分级 基因组和调控状态最终以中性粒细胞或巨噬细胞为特征。髓系细胞正在经历 谱系指定遍历由拮抗基因决定的混合谱系基因表达的连续状态 转录程序(HSCP与髓系祖细胞，然后IRF8与Gfi1)，最终产生 中性粒细胞或单核细胞前体。利用中性粒细胞减少患者来源的突变来转录GFI1 因素，我们建立了先天性中性粒细胞减少症的小鼠模型。为了阐明分子机制 在这些小鼠的体内平衡性中性粒细胞减少和先天免疫功能障碍的基础上，我们首先捕获了正常 包括中性粒细胞规格和承诺的细胞状态，然后建立了一种计算方法来 将中性粒细胞减少模型细胞分配到正常细胞状态并评估基因的细胞状态特异性变异 表情。令人惊讶的是，大多数差异表达的GFI1靶基因顺序改变为 单元格遍历连续的状态。强调这些细胞状态特定的洞察力，基因拯救的影响 规范，但不是在承诺期间设定的先天免疫力。在此，我们建议提供监管 洞察解释了这一发现；定义了改变的Gfi1突变结合和阶段特异的开放染色质。接下来，我们 将决定中性粒细胞防御功能是如何在承诺期间编程的，以及如何在 人类和患有中性粒细胞减少症的小鼠。最后，我们将重温动态平衡背后的基因调控网络。 中性粒细胞与巨噬细胞在建立中性粒细胞动态平衡的背景下的规范 新生儿肠道微生物群定植的波动。我们认为，小鼠对发现的突变进行建模 中性粒细胞减少症患者可以用来揭示中性粒细胞减少症的基本病理生物学，并对其进行解剖。 正常先天免疫功能和粒细胞内稳态建立的机制。 1

SUMMARY Understanding the cellular and molecular processes underlying granulocyte homeostasis is crucial because producing too few granulocytes results in increased risk for infection (neutropenia), while producing too many granulocytes can result in severe tissue damage and death (myeloproliferative disorders). To delineate the molecular mechanisms underlying homeostatic neutrophil production, we previously delineated hierarchical genomic and regulatory states culminating in neutrophil or macrophage specification. Myeloid cells undergoing lineage specification traverse successive states of mixed-lineage gene expression dictated by antagonistic transcriptional programs (HSCP vs. myeloid progenitor, then Irf8 vs. Gfi1) that culminate in generation of neutrophil or monocyte precursors. Using neutropenia-patient-derived mutations in the GFI1 transcription factor, we generated mouse models of congenital neutropenia. To delineate the molecular mechanisms underlying homeostatic neutropenia and innate immune dysfunction in these mice, we first captured normal cell states encompassing neutrophil specification and commitment, then built a computational approach to assign neutropenia-model cells to normal cell states and assess cell-state specific variation in gene expression. Surprisingly, the majority of differentially expressed GFI1-target genes are sequentially altered as cells traverse successive states. Underscoring these cell state-specific insights, genetic rescue impacts specification but not innate immunity programmed during commitment. Here, we propose to provide regulatory insight explaining this finding; defining altered Gfi1-mutant binding and stage-specific open chromatin. Next, we will determine how neutrophil defense functions are programmed during commitment, and how that fails in humans and mice with neutropenia. Finally, we will revisit the gene regulatory network underlying homeostatic neutrophil versus macrophage specification in the context of establishing neutrophil homeostasis through waves of neonatal gut microbiome colonization. We propose that mouse modeling of mutations identified in neutropenic patients can be exploited to reveal the essential pathobiology of neutropenia, and to dissect mechanisms underlying normal innate immune function and the establishment of granulocyte homeostasis. 1