Institute for Cardiovascular Organogenesis and Regeneration, Faculty of Medicine, WWU Münster, Münster, Germany.
Cells-in-Motion Cluster of Excellence, WWU Münster, Münster, Germany.
Angiogenesis. 2021 May;24(2):345-362. doi: 10.1007/s10456-021-09774-w. Epub 2021 Mar 7.
Vegfc/Vegfr3 signaling is critical for lymphangiogenesis, the sprouting of lymphatic vessels. In zebrafish, cells sprouting from the posterior cardinal vein can either form lymphatic precursor cells or contribute to intersegmental vein formation. Both, the Vegfc-dependent differential induction of Prox1a in sprouting cells as well as a Notch-mediated pre-pattern within intersegmental vessels have been associated with the regulation of secondary sprout behavior. However, how exactly a differential lymphatic versus venous sprout cell behavior is achieved is not fully understood. Here, we characterize a zebrafish mutant in the adaptor protein Grb2b, and demonstrate through genetic interaction studies that Grb2b acts within the Vegfr3 pathway. Mutant embryos exhibit phenotypes that are consistent with reduced Vegfr3 signaling outputs prior to the sprouting of endothelial cells from the vein. During secondary sprouting stages, loss of grb2b leads to defective cell behaviors resulting in a loss of parachordal lymphangioblasts, while only partially affecting the number of intersegmental veins. A second GRB2 zebrafish ortholog, grb2a, contributes to the development of lymphatic structures in the meninges and in the head, but not in the trunk. Our results illustrate an essential role of Grb2b in vivo for cell migration to the horizontal myoseptum and for the correct formation of the lymphatic vasculature, while being less critically required in intersegmental vein formation. Thus, there appear to be higher requirements for Grb2b and therefore Vegfr3 downstream signaling levels in lymphatic versus vein precursor-generating sprouts.
Vegfc/Vegfr3 信号通路对于淋巴管生成（淋巴管的萌芽）至关重要。在斑马鱼中，从后主静脉萌芽的细胞可以分化为淋巴管前体细胞或参与节间静脉的形成。Vegfc 依赖性地诱导芽生细胞中 Prox1a 的差异表达，以及 Notch 介导的节间血管内的预模式，都与次级芽生行为的调节有关。然而，如何精确地实现淋巴管与静脉芽生细胞行为的差异仍然不完全清楚。在这里，我们对衔接蛋白 Grb2b 的斑马鱼突变体进行了描述，并通过遗传相互作用研究表明，Grb2b 作用于 Vegfr3 信号通路内。突变体胚胎表现出的表型与内皮细胞从静脉萌芽前 Vegfr3 信号输出减少一致。在次级萌芽阶段，grb2b 的缺失导致细胞行为缺陷，导致 parachordal 淋巴管母细胞缺失，而仅部分影响节间静脉的数量。第二个 GRB2 斑马鱼同源物 grb2a 有助于脑膜和头部的淋巴管结构的发育，但不在躯干中。我们的结果表明，Grb2b 在体内对于细胞迁移到水平肌膜和正确形成淋巴管血管系统具有重要作用，而在节间静脉形成中则不太重要。因此，在淋巴管前体细胞生成芽中，Grb2b 和因此 Vegfr3 下游信号水平似乎比静脉前体细胞生成芽的要求更高。
