Coordination of cell cycle, metabolism, and myeloid differentiation by lineage-specific transcription factors

生物学中的一个中心问题是了解细胞和有机体如何调节细胞分裂，以响应发育和环境提示。在血细胞发育过程中，静止的造血干细胞产生快速增殖的祖细胞。随着祖细胞分化为成熟细胞，它们会逐渐放慢细胞周期时钟的速度，并诱导基因表达的变化。越来越多的证据表明，造血细胞分化过程中的代谢变化是细胞周期时钟的重要输入。这种分化过程是在特定细胞类型的转录因子的控制下进行的。关于细胞类型特异性转录因子协调细胞周期停滞与分化的机制仍有许多有待了解。*PU.1(由Spi1基因编码)是一个E26-转换特异性(ETS)家族转录因子，是一种浓度依赖的血细胞分化调节因子。巨噬细胞和髓系祖细胞的分化伴随着分化所需的PU.1浓度上调5倍。由突变或抑制引起的PU.1表达降低会导致未成熟髓系祖细胞的增殖增加和分化障碍。在造血干细胞中，PU1表达降低与细胞周期紊乱有关。该研究计划的长期目标是确定PU.1等转录因子如何协调髓系细胞的细胞周期、代谢变化和终末分化。*我们建议使用我们实验室开发的PU.1诱导的BN细胞系系统以及体内自我更新的巨噬细胞群来确定PU.1对细胞周期停滞、代谢变化和分化的协调机制。我们的计划目标将解决四个问题：1)PU.1是否直接或间接地控制由PU1直接结合的基因编码的mRNA的下调？2)PU.1如何下调关键直接靶基因的mRNA水平？3)PU.1诱导的mRNAs下调是由负责细胞周期停滞的脂肪酸代谢相关基因编码的吗？或者细胞周期停滞控制脂肪酸代谢？4)PU.1水平在常驻巨噬细胞群体的自我更新中发挥作用吗？*这些实验有望导致对PU.1如何调节髓系分化和自我更新的详细了解。

A central problem in biology is to understand how cells and organisms regulate cell division in response to developmental and environmental cues. During blood cell development, quiescent hematopoietic stem cells generate rapidly proliferating progenitor cells. As progenitor cells differentiate into mature cells, they gradually slow the rate of their cell cycle clock and induce changes in gene expression. There is emerging evidence that metabolic changes during hematopoietic differentiation are an important input into the cell cycle clock. This differentiation process is under the control of cell-type-specific transcription factors. Much remains to be learned about mechanisms by which cell type specific transcription factors coordinate cell cycle arrest with differentiation.****PU.1 (encoded by the Spi1 gene) is an E26-transformation specific (ETS) family transcription factor that is a concentration-dependent regulator of blood cell differentiation. Differentiation of macrophages from myeloid progenitors is accompanied by a 5-fold upregulation of PU.1 concentration that is required for differentiation. Reduced PU.1 expression caused by mutation or repression leads to increased proliferation and impaired differentiation of immature myeloid progenitor cells. Reduced PU.1 expression is associated with deregulated cell cycle in hematopoietic stem cells. The long-term goal of this research program is to determine how cell cycle, metabolic changes, and terminal differentiation of myeloid cells are coordinated by transcription factors such as PU.1.****We propose to use a PU.1-inducible BN cell line system developed in our laboratory as well as in vivo self-renewing macrophage populations to determine the mechanism of coordination of cell cycle arrest, metabolic changes and differentiation by PU.1. There are four questions that will be addressed by our program goals: 1) Does PU.1 directly or indirectly control the downregulation of mRNA encoded by genes that are directly bound by PU.1? 2) How does PU.1 downregulate mRNA levels for key direct target genes? 3) Is PU.1-induced downregulation of mRNAs encoded by genes involved fatty acid metabolism in charge of cell cycle arrest, or does cell cycle arrest control fatty acid metabolism? 4) Do PU.1 levels play a role in self-renewal of resident macrophage populations?****These experiments are expected to result in a detailed understanding of how PU.1 regulates myeloid differentiation and self-renewal.**