The DNA damage response of fast-cycling erythroblasts

红细胞生成或红细胞形成的过程在整个生命过程中是连续的。其 一项研究有助于阐明红细胞疾病，最明显的是贫血，占所有残疾的8.8% 在全球它也是研究发育生物学基本问题的一个可用模型。这 一项建议是基于最近的发现，即一个关键的红细胞命运决定与戏剧性的 S期缩短。在其他一些发育系统中，细胞命运的决定也类似地与一个基因相关。 更快的S阶段。更快的S期可能是以基因组不稳定为代价的，如在癌基因中， 诱导复制应激。然而，对生理上更快的S期和 正常发育中DNA损伤反应缺乏。本项目的目标是确定 红细胞发育转换的异常快速S期需要改变DNA复制保真度和/或 DNA损伤反应的改变。 早期红系祖细胞，称为“红系集落形成单位”（CFU-e）， 在转变为红细胞终末分化（ETD）之前，它们开始表达红细胞 基因.从自我更新的CFU-e祖细胞到成熟的ETD成红细胞的转变是一个快速的过程。 转录开关，其与单细胞周期S期同步并依赖于单细胞周期S期。引人注目的是， CFU-e/ETD转换的S期持续时间非常短，仅持续4小时，而对照组为7小时。 CFU-e周期之前，由于复制分叉速度整体提高了50%。这些变化 CFU-e/ETD转换需要S期速度; CFU-e祖细胞的较慢S期促进CFU-e/ETD转换。 它们的自我更新，而早期ETD的快速S期促进红系基因诱导。预期可能 早期ETD成红细胞的快速S期将导致复制叉停滞事件的增加 （“复制压力”）和增加的基因组不稳定性。我们的实验性AIMS测试了两个相反的， 必然相互排斥的假设： 假设1：早期ETD的更快S期是以较低质量的复制为代价的。 假设2：早期ETD的更快的S期反映了“增压”的复制偶联DNA修复。 AIM 1将分析快速循环早期ETD成红细胞中DNA复制的质量。AIM 2将确定 快速循环的ETD成红细胞的DNA损伤反应如何不同于其缓慢循环的CFU- e前体。AIM 3将确定是否更快的S期和改变的DNA损伤反应， ETD在基因上是可分离的。

Project Summary Erythropoiesis, or the process of red cell formation, is continuous throughout life. Its study helps elucidate erythroid disorders, most notably anemia, which accounts for 8.8% of all disability globally. It is also an accessible model for studying fundamental questions in developmental biology. This proposal is based on recent finding that a key erythroid cell fate decision is associated with dramatic shortening of S phase. Cell fate decisions in some other developmental systems are similarly associated with a faster S phase. A faster S phase might be accomplished at the cost of genomic instability, as in oncogene- induced replicative stress. However, studies of the relationships between a physiologically faster S phase and the DNA damage response in normal development are lacking. This project’s goal is to determine whether the unusually fast S phase of the erythroid developmental switch entails altered DNA replication fidelity and/or alterations in the DNA damage response. Early erythroid progenitors, termed ‘colony-forming-unit-erythroid’ (CFU-e), undergo several self-renewal cell divisions before transitioning into Erythroid Terminal Differentiation (ETD), where they begin to express red cell genes. The transition from self-renewing CFU-e progenitors to maturing ETD erythroblasts is a rapid transcriptional switch that is synchronized with, and dependent on, a single cell cycle S phase. Strikingly, the S-phase of the CFU-e/ETD switch is of uniquely short duration, lasting only 4 hr, compared with 7 hr in preceding CFU-e cycles, as a result of a global, 50% increase in the speed of replication forks. These changes in S phase speed are required for the CFU-e/ETD switch; the slower S phase of CFU-e progenitors promotes their self-renewal, while the fast S phase of early ETD promotes erythroid gene induction. It might be expected that the fast S phase of early ETD erythroblasts would exact a ‘cost’ of increased replication fork stalling events (‘replication stress’) and increased genomic instability. our experimental AIMS test two opposing but not necessarily mutually exclusive hypotheses: Hypothesis 1: The faster S phase of early ETD is achieved at a cost of lower quality replication. Hypothesis 2: The faster S phase of early ETD reflects “supercharged” replication-coupled DNA repair. AIM 1 will analyze the quality of DNA replication in fast-cycling early ETD erythroblasts. AIM 2 will determine how the DNA damage response of fast-cycling ETD erythroblasts differs from that of their slower-cycling CFU- e precursors. AIM 3 will determine whether the faster S phase and the altered DNA damage response of early ETD are genetically separable.