Long non-coding RNA regulation of short-lived myeloid homeostasis

项目摘要 中性粒细胞、嗜酸性粒细胞和“经典”单核细胞是抵御几乎所有病原体的第一道防线。不足为奇的是，这些炎性细胞也极易损害宿主组织。这些细胞的寿命受到严格的调节，以平衡保护性免疫和免疫病理。尽管众所周知，细胞外促生存因素影响这些细胞的寿命，但细胞外信号如何转化为最佳的细胞寿命在很大程度上是未知的。最近有证据表明，大多数人类基因组不为蛋白质编码，而非编码区被转录。事实上，长的非编码RNA(LncRNA)转录本已经被证明是基因表达的关键控制因素。越来越多的证据表明，lncRNAs通过组蛋白修饰在将细胞外信号转化为基因表达程序中起着关键作用。鉴于细胞外因素对中性粒细胞、嗜酸性粒细胞和“经典”单核细胞的寿命和功能的强烈影响，我们推测细胞外信号诱导的lncRNAs对于精确调控这些髓系细胞的存活至关重要。通过高通量测序，我们通过全基因组关联研究(GWAS)发现了一个在小鼠和人的短寿命髓系细胞中高度特异表达的lncRNA(Gm14005)，并与人类炎症性疾病相关。在小鼠中，这种lncRNA的缺失导致了短暂的髓系细胞存活和数量的严重缺陷。 为了进一步验证我们的假设，我们提出了以下具体目标：目标1将利用我们的IncRNA缺陷小鼠模型来研究Gm14005在短期髓系细胞动态平衡中的作用。我们将确定Gm14005在发育过程中何时控制生存，哪些细胞外信号调节Gm14005的表达，以及Gm14005在炎症过程中的作用P目的2将研究Gm14005在体内发挥作用的分子机制。我们的初步证据表明，Gm14005缺陷的短寿命髓系细胞高度过度表达邻近的促凋亡基因Bcl211(Bim)。此外，在Gm14005基因缺失的小鼠中，Bcl2l11的缺失挽救了短暂的髓系数量。我们将研究Gm14005是否控制组蛋白修饰和Bcl2L11基因的染色质可及性，以及该lncRNA是否与抑制性染色质重塑蛋白复合体相互作用。这些研究将对短暂的髓系细胞寿命如何受到严格调控以及lncRNAs在免疫稳态中的作用这一基本但基本上未知的过程提供关键的见解。由于Gm14005也在人类短暂的髓系细胞中高度和特异地表达，这些见解可能有助于开发新的策略来治疗以髓系寿命失调为特征的人类疾病。

Project Summary Neutrophils, eosinophils and “classical” monocytes represent a first line of defense against nearly all pathogens. Not surprisingly, these inflammatory cells are also highly prone to damaging host tissue. The lifespan of these cells is strictly regulated to balance protective immunity with immunopathology. Although, extracellular pro-survival factors are well known to influence the lifespan of these cells, how extracellular cues are translated into an optimal cellular lifespan is largely unknown. It has recently become evident that the majority of the human genome does not encode for proteins and noncoding regions are transcribed. Indeed, long noncoding RNA (lncRNA) transcripts have been demonstrated to be key controllers of gene expression. Emerging evidence indicates that lncRNAs play a critical role in translating extracellular signals into gene expression programs through histone modifications. Given the strong influence of extracellular factors on the lifespan and function of neutrophils, eosinophils and “classical” monocytes, we postulate that lncRNAs induced by extracellular cues are critical for precisely regulating the survival of these myeloid cells. Using high-throughput sequencing, we identified a lncRNA (Gm14005) that is highly and specifically expressed by murine and human short-lived myeloid cells, and associated with human inflammatory diseases through genome wide association studies (GWAS). Deletion of this lncRNA in mice results in a profound defect in short-lived myeloid cell survival and numbers. To further test our hypothesis, we proposed the following Specific Aims: Aim 1 will utilize our lncRNA-deficient mouse model to investigate the role of Gm14005 in short-lived myeloid cell homeostasis. We will determine when during development Gm14005 controls survival, what extracellular signals regulate Gm14005 expression, and the role of Gm14005 during inflammationP Aim 2 will examine the molecular mechanism through which Gm14005 acts in vivo. Our preliminary evidence demonstrates that Gm14005-deficient short lived myeloid cells highly overexpress the neighboring pro-apoptotic gene, Bcl2l11 (Bim). Additionally, deletion of Bcl2l11 in Gm14005-deficient mice rescues short-lived myeloid numbers. We will investigate whether Gm14005 controls the histone modifications and chromatin accessibility at the Bcl2l11 locus, and whether this lncRNA interacts with repressive chromatin remodeling protein complexes. These studies will provide key insights into the fundamental but largely unknown process of how short-lived myeloid cell lifespan is tightly regulated, and function of lncRNAs in immune homeostasis. As Gm14005 is also highly and specifically expressed by human short-lived myeloid cells, these insights may aid the development of new strategies to treat human diseases characterized by dysregulated myeloid lifespan.