Constrained Fetal Hematopoiesis and Clonal Restriction in Fanconi Anemia

摘要 该方案基于我们的发现探索了范可尼贫血(FA)发病的新模式。 蛋白质保护造血干细胞在快速发育过程中免受复制应激的影响 胎儿肝脏扩张(FL)。FA是一种隐性遗传性DNA修复障碍，具有癌症易感性 近乎均匀的骨髓(BM)衰竭。而大多数FA患者在早期就经历了症状性衰竭 在学龄期，骨髓造血干细胞(HSC)的数量在生命的早期就已经受损。我们 最近报道，FA基因敲除小鼠的HSC生理缺陷发生在子宫内。我们现在 结果表明，FA缺陷首先出现在FL，由复制应激相关的ATR/Chk1检查点引起 参与免疫表型定义的HSC。因为HSC池通常在出生时就已经完成， 这些限制不仅构成了在FA形成HSC池之前未被认识到的瓶颈，而且 也是导致出生后HSC迅速耗尽的主要危险因素。理解被夸大的事物 足总外语中的发育脆弱性我们已经对外语进行了额外的初步研究 一种微环境，涉及形成HSC生态位的支持细胞的子集。总而言之，我们 假设FA蛋白的生理作用是保护HSC池克隆和基因组 在复制胁迫条件下的完整性。这些观察结果让我们测试了以下因素的长期影响 胎儿FA对HSC自我更新和造血储备的影响。 具体目标1可确定绝对HSC池大小和克隆多样性是以下疾病的驱动风险因素 FA中的HSC耗尽 具体目标2：剖析检查点激活对基因组稳定性和 胎儿FA-HSC的功能 特定目标3：识别导致造血缺陷的FL特定小生境异常 并揭示了在功能上限制HSC扩展的关键信号通路 总而言之，该项目提出了一种新的范式，使FA蛋白能够实现发育扩张 以及自我更新分裂对克隆多样性和HSC池中基因组的稳定性至关重要。这个职位 FA患者的发育缺陷是HSC衰竭的驱动危险因素和关键原因 发病率和死亡率。研究结果将为安全有效的新疗法的开发提供洞察力 减轻FA患者的造血功能丧失。

Summary This proposal explores a new model of Fanconi Anemia (FA) pathogenesis based on our findings that FA proteins protect hematopoietic stem cells (HSCs) from replication stress during the rapid developmental expansion in the fetal liver (FL). FA is a recessively inherited DNA repair disorder with cancer predisposition and near uniform bone marrow (BM) failure. While most FA patients experience symptomatic failure in early school age, BM hematopoietic stem cell (HSC) numbers are already compromised much earlier in life. We recently reported that the physiologic onset of HSC deficits in FA knockout mice occurs in utero. We now show that deficits in FA first emerge in the FL, caused by replication stress-associated Atr/Chk1 checkpoint engagement in immunophenotypically defined HSC. Because the HSC pool is typically complete at birth, these constraints constitute not only a previously unrecognized bottleneck for HSC pool formation in FA, but also pose a principal risk factor for rapid postnatal HSC exhaustion. To understand the exaggerated developmental vulnerability in the FA FL we have conducted additional preliminary studies of the FL microenvironment that implicate a subset of supportive cells forming the HSC niche. Altogether, we hypothesize that the physiological role of FA proteins is to safeguard in HSC pool clonality and genome integrity under conditions of replication stress. These observations lead us to test the long-term impact of fetal deficits in FA on HSC self-renewal and hematopoietic reserve. Specific Aim 1 ïDetermine absolute HSC pool size and clonal diversity as driving risk factors for HSC exhaustion in FA Specific Aim 2 ïDissect the long-term impact of checkpoint activation on genome stability and function in fetal FA HSC Specific Aim 3 ïIdentify the FL specific niche abnormalities that contribute to hematopoietic deficits in FA, and reveal the key signaling pathways that functionally limit HSC expansion Altogether, this project advances a new paradigm, whereby FA proteins enable developmental expansion and self-renewal divisions critical to clonal diversity and genome stability in the HSC pool. This positions developmental deficits in FA patients as a driving risk factor for HSC exhaustion and a critical cause for morbidity and mortality. Results will provide insight for the development of safe and effective new therapies that mitigate loss of hematopoietic function in FA.