Department of Developmental Genetics, Skirball Institute of Molecular Medicine, New York City, New York 10016, USA.
Dev Biol. 2011 Sep 1;357(1):134-51. doi: 10.1016/j.ydbio.2011.06.037. Epub 2011 Jul 1.
The brain is made of billions of highly metabolically active neurons whose activities provide the seat for cognitive, affective, sensory and motor functions. The cerebral vasculature meets the brain's unusually high demand for oxygen and glucose by providing it with the largest blood supply of any organ. Accordingly, disorders of the cerebral vasculature, such as congenital vascular malformations, stroke and tumors, compromise neuronal function and survival and often have crippling or fatal consequences. Yet, the assembly of the cerebral vasculature is a process that remains poorly understood. Here we exploit the physical and optical accessibility of the zebrafish embryo to characterize cerebral vascular development within the embryonic hindbrain. We find that this process is primarily driven by endothelial cell migration and follows a two-step sequence. First, perineural vessels with stereotypical anatomies are formed along the ventro-lateral surface of the neuroectoderm. Second, angiogenic sprouts derived from a subset of perineural vessels migrate into the hindbrain to form the intraneural vasculature. We find that these angiogenic sprouts reproducibly penetrate into the hindbrain via the rhombomere centers, where differentiated neurons reside, and that specific rhombomeres are invariably vascularized first. While the anatomy of intraneural vessels is variable from animal to animal, some aspects of the connectivity of perineural and intraneural vessels occur reproducibly within particular hindbrain locales. Using a chemical inhibitor of VEGF signaling we determine stage-specific requirements for this pathway in the formation of the hindbrain vasculature. Finally, we show that a subset of hindbrain vessels is aligned and/or in very close proximity to stereotypical neuron clusters and axon tracts. Using endothelium-deficient cloche mutants we show that the endothelium is dispensable for the organization and maintenance of these stereotypical neuron clusters and axon tracts in the early hindbrain. However, the cerebellum's upper rhombic lip and the optic tectum are abnormal in clo. Overall, this study provides a detailed, multi-stage characterization of early zebrafish hindbrain neurovascular development with cellular resolution up to the third day of age. This work thus serves as a useful reference for the neurovascular characterization of mutants, morphants and drug-treated embryos.
大脑由数十亿个高度代谢活跃的神经元组成，其活动为认知、情感、感觉和运动功能提供了基础。脑脉管系统通过为大脑提供最大的血液供应来满足其对氧气和葡萄糖的极高需求，这是任何器官中最大的血液供应。因此，脑脉管系统的疾病，如先天性血管畸形、中风和肿瘤，会损害神经元的功能和存活，并且常常导致致残或致命的后果。然而，脑脉管系统的组装过程仍然知之甚少。在这里，我们利用斑马鱼胚胎的物理和光学可及性来描述胚胎后脑血管的发育。我们发现，这个过程主要由内皮细胞迁移驱动，并遵循两步序列。首先，具有典型解剖结构的神经周围血管沿着神经外胚层的腹外侧表面形成。其次，来自神经周围血管亚群的血管生成芽从神经周围血管迁移到后脑形成神经内血管。我们发现，这些血管生成芽可以通过已经分化的神经元所在的神经节中心重复地穿透后脑，并且特定的神经节总是首先被血管化。虽然神经内血管的解剖结构在不同动物之间有所不同，但神经周围和神经内血管的某些连接在特定的后脑区域内具有可重复性。我们使用 VEGF 信号通路的化学抑制剂来确定该通路在形成后脑脉管系统中的特定阶段的要求。最后，我们发现一部分后脑血管与典型的神经元簇和轴突束对齐和/或非常接近。我们使用内皮细胞缺陷型 cloche 突变体证明，在早期后脑中，内皮细胞对于这些典型神经元簇和轴突束的组织和维持是可有可无的。然而，clo 中的小脑上菱形唇和视顶盖是异常的。总的来说，这项研究提供了早期斑马鱼后脑神经血管发育的详细、多阶段的特征描述，具有高达 3 天大的细胞分辨率。因此，这项工作为突变体、形态发生和药物处理胚胎的神经血管特征描述提供了有用的参考。
