Hogan Benjamin M, Herpers Robert, Witte Merlijn, Heloterä Hanna, Alitalo Kari, Duckers Henricus J, Schulte-Merker Stefan
Hubrecht Institute-KNAW & University Medical Centre, Utrecht, and Centre for Biomedical Genetics, Uppsalalaan 8, 3584 CT Utrecht, The Netherlands.
Development. 2009 Dec;136(23):4001-9. doi: 10.1242/dev.039990.
The development of arteries, veins and lymphatics from pre-existing vessels are intimately linked processes controlled by a number of well-studied reiteratively acting signalling pathways. To delineate the mechanisms governing vessel formation in vivo, we performed a forward genetic screen in zebrafish and isolated the mutant expando. Molecular characterisation revealed a loss-of-function mutation in the highly conserved kinase insert region of flt4. Consistent with previous reports, flt4 mutants were deficient in lymphatic vascular development. Recent studies have demonstrated a role for Flt4 in blood vessels and showed that Dll4 limits angiogenic potential by limiting Flt4 function in developing blood vessels. We found that arterial angiogenesis proceeded normally, yet the dll4 loss-of-function arterial hyperbranching phenotype was rescued, in flt4 signalling mutants. Furthermore, we found that the Flt4 ligand Vegfc drives arterial hyperbranching in the absence of dll4. Upon knockdown of dll4, intersegmental arteries were sensitised to increased vegfc levels and the overexpression of dll4 inhibited Vegfc/Flt4-dependent angiogenesis events. Taken together, these data demonstrate that dll4 functions to suppress the ability of developing intersegmental arteries to respond to Vegfc-driven Flt4 signalling in zebrafish. We propose that this mechanism contributes to the differential response of developing arteries and veins to a constant source of Vegfc present in the embryo during angiogenesis.
动脉、静脉和淋巴管由先前存在的血管发育而来，这是一些紧密相连的过程，受许多经过充分研究的反复作用的信号通路控制。为了阐明体内血管形成的机制，我们在斑马鱼中进行了正向遗传学筛选，并分离出了突变体expando。分子特征分析显示，在高度保守的flt4激酶插入区域存在功能丧失突变。与之前的报道一致，flt4突变体在淋巴管发育方面存在缺陷。最近的研究表明Flt4在血管中发挥作用，并表明Dll4通过限制Flt4在发育中的血管中的功能来限制血管生成潜能。我们发现动脉血管生成正常进行，但在flt4信号突变体中，dll4功能丧失的动脉过度分支表型得到了挽救。此外，我们发现Flt4配体Vegfc在没有dll4的情况下会驱动动脉过度分支。在敲低dll4后，节间动脉对vegfc水平升高变得敏感，而dll4的过表达抑制了Vegfc/Flt4依赖的血管生成事件。综上所述，这些数据表明，dll4的功能是抑制斑马鱼发育中的节间动脉对Vegfc驱动的Flt4信号作出反应的能力。我们提出，这一机制有助于发育中的动脉和静脉对血管生成过程中胚胎中持续存在的Vegfc来源作出不同的反应。
