Regulation of lymphatic endothelial cell specification

项目摘要 淋巴循环是一个独特的血管网络，由专门的淋巴管内皮细胞排列 （LEC），其帮助调节组织流体稳态、免疫细胞运输和脂质吸收。中断 淋巴管发育导致原发性先天性水肿，影响33，000个活产婴儿中的1个。 对于水肿没有有效的治疗方法，目前的治疗方法只能帮助减轻疾病的症状。 我们必须更好地理解调节淋巴发育的机制， 确定治疗水肿、脂肪吸收不良和免疫缺陷的新的治疗靶点， 监视淋巴循环在胚胎中发展，在血液形成后不久 在一系列步骤中，包括特化、迁移和成熟，以形成成人淋巴管。 流通在早期胚胎发育中，主静脉中的静脉内皮细胞亚群被指定 成为LECs。新分化的淋巴管内皮细胞从主静脉中迁移出来，形成原始毛细淋巴管 淋巴管丛，在发育后期被重塑为成熟的淋巴循环。虽然进展 淋巴管发育的调控机制已经有了很好的描述，但其机制仍有很多未知之处 规范LEC规范。内皮祖细胞响应于无数的信号线索， 血液、生血或淋巴内皮结局。最近，细胞周期状态已被确定为 重要的调节因子，使不同的内皮亚型的规格。我们以前的工作 实验室已经确定细胞周期停滞在早期G1期，以使静脉和生血内皮特化，而 晚期G1期阻滞促进动脉命运决定。因此，不同的内皮细胞周期状态动态地 通过为不同的命运承诺创造“机会之窗”来调节内皮细胞表型。虽然 人们越来越认识到细胞周期控制在血液和造血内皮细胞中的作用， 说明书中，其在早期胚胎发生期间对LEC命运定型的贡献仍然未被探索。我们 初步数据表明，细胞周期控制的破坏损害了正常LEC的特化和淋巴细胞增殖。 血管成熟，支持淋巴发育过程中细胞周期调控的关键作用。这项建议 将检验G1期细胞周期阻滞使静脉内皮细胞的LEC特化的假设， 早期胚胎发生使用Fucci细胞周期报告小鼠，其中可以辨别不同的细胞周期状态， 和新的LEC特异性基因敲除小鼠模型，我们将研究调节 内皮细胞周期控制和LEC规格在发展过程中。这些研究的结果将有助于 了解在淋巴管发育过程中发挥作用的关键机制，并可能阐明新的 用于治疗原发性痤疮的治疗靶点。

Project Summary The lymphatic circulation is a unique network of vessels lined by specialized lymphatic endothelial cells (LECs), which help regulate tissue fluid homeostasis, immune cell transport, and lipid absorption. Disruption in lymphatic vascular development leads to primary congenital lymphedema affecting 1 in 33,000 live born infants. There are no effective cures for lymphedema, and current therapies only help mitigate symptoms of the disease. It’s imperative to acquire a better understanding of the mechanisms that regulate lymphatic development in order to identify novel therapeutic targets for the treatment of lymphedema, fat malabsorption and immune surveillance. The lymphatic circulation develops in the embryo, shortly after the formation of the blood vasculature, in a series of steps including specification, migration and maturation to form the adult lymphatic circulation. In early embryonic development, a subset of venous endothelial cells in the cardinal vein are specified to become LECs. Newly specified LECs migrate out of the cardinal vein forming the primitive lymphatic capillary plexus, which is remodeled into the mature lymphatic circulation later in development. Although the progression of lymphatic vascular development has been well described, there is still a lot unknown about the mechanisms regulating LEC specification. Endothelial progenitor cells respond to a myriad of signaling cues to specify into either blood, hemogenic or lymphatic endothelial fates. Recently, cell cycle state has been identified as an important regulatory factor enabling the specification of different endothelial subtypes. Previous work from our lab has identified cell cycle arrest in early G1 to enable venous and hemogenic endothelial specification, whereas late G1 arrest promotes arterial fate determination. Thus, different endothelial cell cycle states dynamically regulate endothelial cell phenotype by creating “windows of opportunity” for different fate commitments. Although there is a growing appreciation for the role of cell cycle control in blood and hemogenic endothelial cell specification, its contribution to LEC fate commitment during early embryogenesis remains unexplored. Our preliminary data show that disruption of cell cycle control impairs normal LEC specification and lymphatic vascular maturation, supporting a key role for cell cycle regulation during lymphatic development. This proposal will test the hypothesis that G1 cell cycle arrest enables LEC specification from venous endothelial cells during early embryogenesis. Using Fucci cell cycle reporter mice in which distinct cell cycle states can be discerned, and novel LEC-specific knockout mouse models, we will investigate the underlying mechanisms regulating endothelial cell cycle control and LEC specification during development. Results from these studies will help to understand the key mechanisms at play during lymphatic vascular development and may elucidate novel therapeutic targets for the treatment of primary lymphedemas.