The RNA helicase Ddx21 controls Vegfc-driven developmental lymphangiogenesis by balancing endothelial cell ribosome biogenesis and p53-p21 signalling [zebrafish]

The development of a differentiated and functional vasculature requires coordinated control of cell fate specification, lineage differentiation and vascular network growth. Cellular proliferation is spatiotemporally regulated in developing vessel networks but how this is achieved and differentially controlled in specific lineages is unknown. Using a zebrafish forward genetic screen for mutants that form blood vessels but fail to form lymphatic vessels, we uncovered a mutant for the RNA helicase Ddx21. Ddx21 cell-autonomously regulates the early development of lymphatic endothelial cells. Ddx21 is essential for Vegfc-Vegfr3 driven endothelial cell proliferation. Ddx21 is an established regulator of ribosomal RNA transcription and in the absence of Ddx21, mutant lymphatic endothelial cells show reduced ribosome biogenesis. Ultimately, loss of Ddx21 leads to a p53-p21 dependent cell cycle arrest that blocks embryonic lymphangiogenesis. Thus, the RNA helicase Ddx21 coordinates the endothelial cell proliferative response to Vegfc-Vegfr3 signalling by balancing ribosome biogenesis and p53-p21 signalling. This mechanism may have therapeutic potential in diseases of excessive lymphangiogenesis such as in cancer metastasis or lymphatic malformation. LEC and VEC RNA profiles on sibling and ddx21 mutant cells obtained from zebrafish embryos

具有差异化功能的脉管系统的发育，需要对细胞命运特化、谱系分化以及血管网络生长进行协同调控。在发育中的血管网络内，细胞增殖受到时空特异性调控，但目前尚不明确该调控的实现方式，以及其在特定细胞谱系中实现差异调控的具体机制。我们通过斑马鱼正向遗传筛选，针对仅能形成血管却无法生成淋巴管的突变体展开研究，最终发现了RNA解旋酶Ddx21（RNA helicase Ddx21）的功能缺失突变体。Ddx21以细胞自主性方式调控淋巴管内皮细胞的早期发育进程。Ddx21是介导Vegfc-Vegfr3信号通路驱动的内皮细胞增殖所必需的关键因子。Ddx21作为公认的核糖体RNA转录调控因子，在缺失Ddx21的突变淋巴管内皮细胞中，核糖体生物发生水平显著降低。最终，Ddx21的缺失会引发依赖于p53-p21通路的细胞周期阻滞，从而阻断胚胎淋巴管生成过程。综上，RNA解旋酶Ddx21通过平衡核糖体生物发生与p53-p21信号通路，协同调控内皮细胞对Vegfc-Vegfr3信号的增殖响应。该调控机制在肿瘤转移、淋巴管畸形等过度淋巴管生成相关疾病中具有潜在的治疗应用价值。本数据集包含从斑马鱼胚胎中分离得到的同窝对照与ddx21突变体细胞的淋巴管内皮细胞（lymphatic endothelial cell, LEC）及血管内皮细胞（vascular endothelial cell, VEC）转录组谱。