VEGF regulation of neurogenesis

描述（由申请人提供）：这项工作的总体目标是研究大脑形成过程中神经细胞和血管细胞之间发育通讯的调节分子机制。本研究旨在探讨血管内皮生长因子A （vascular endothelial growth factor A， VEGF）在早期皮质神经发生中的作用及其机制。这项研究的结果将澄清我们对VEGF在神经发生过程中调节血管和神经细胞存活和分化能力的双重性质的理解。了解神经系统对损伤或应激反应的潜力，无论是在发育过程中还是在成人中，关键在于在脉管系统的背景下控制神经发生的调节机制。从历史上看，VEGF已被研究为血管生成的有效调节剂（见1）。然而，最近的研究表明VEGF在神经系统中的作用扩大了（见2,3）。在细胞外基质和细胞表面，VEGF通过选择性剪接产生大小和与硫酸肝素蛋白聚糖结合能力不同的同种异构体4。同种异构体的后一种特性允许VEGF在细胞微环境中建立可扩散和局部保留的信号梯度。尽管许多研究表明VEGF在神经系统中发挥作用，例如在血管形成中2,3，但对VEGF在神经发生中的直接作用知之甚少。在NINDS之前的支持下（1 R15 NS057807-01），我们已经确定了三种主要的VEGF亚型和VEGF受体在小鼠大脑神经上皮发育的关键窗口中存在差异表达。此外，在仅表达可扩散的VEGF120异构体或仅局部保留的VEGF188异构体的转基因小鼠模型中，pax6阳性的神经干细胞群体减少。结果，tbr2阳性中间祖细胞的正常表达模式被破坏，而这对早期皮层的建立至关重要。拟议的研究将验证这样的假设，即VEGF同种异构体建立了一个梯度，调节pax6阳性神经干细胞的增殖和分化，促进皮层正常层的形成。该假设将通过以下目标进行检验。目标# 1。利用表达单一VEGF亚型或VEGF亚型组合的小鼠，评估VEGF亚型在调节早期皮质发育中的作用。目标# 2。目的：探讨神经和血管细胞成分异型细胞培养模型中VEGF亚型作用的机制。这一建议的结果对于确定神经和血管系统之间的异型细胞-细胞相互作用如何调节早期脑形成中的神经发生将是重要的。

DESCRIPTION (provided by applicant): The overall objective of this work is to investigate the molecular mechanisms that regulate developmental communication between neural and vascular cells as the brain forms. The goal of the proposed research is to investigate the role of vascular endothelial growth factor A (VEGF) and its mechanism of action in regulating early cortical neurogenesis. The results from this study will clarify our understanding of the dual nature of VEGF in its ability to regulate survival and differentiation of vascular and neural cells during neurogenesis. The key to understanding the potential of the nervous system to respond to damage or stress, whether during development or in the adult, lies in the regulatory mechanisms that control neurogenesis in the context of the vasculature. Historically, VEGF has been investigated as a potent regulator of angiogenesis (reviewed in1). However, more recent investigations have suggested an expanded role for VEGF in the nervous system (reviewed in 2, 3). VEGF undergoes alternative splicing to generate isoforms that differ in their size and ability to bind to heparan sulfate proteoglycans in the extracellular matrix and on the cell surface4. This latter property of the isoforms allows VEGF to establish a gradient of diffusible and locally retained signals in the cellular microenvironment. Although a number of studies have suggested a role for VEGF in the nervous system, for example in blood vessel patterning2, 3, little is known about the direct role that VEGF plays in neurogenesis. With previous support from NINDS (1 R15 NS057807-01), we have determined that the three major VEGF isoforms and VEGF receptors are differentially expressed during a key window of neuralepithelial development in the mouse brain. Moreover, a Pax6-positive population of neural stem cells is reduced in a transgenic mouse model expressing only the diffusible VEGF120 isoform or only the locally-retained VEGF188 isoform. As a consequence, the normal expression pattern of Tbr2-positive intermediate progenitor cells, critical for early cortical layer establishment, is disrupted. The proposed research will test the hypothesis that the VEGF isoforms establish a gradient that regulates the proliferation and differentiation of Pax6-positive neural stem cells contributing to normal layer formation in the cortex. The hypothesis will be tested with the following aims. Aim #1. To assess the role of the VEGF isoforms in regulating early cortical development using mice expressing single VEGF isoforms or combinations of VEGF isoforms. Aim #2. To identify the mechanism of VEGF isoform action in a heterotypic cell culture model incorporating neural and vascular cell components. The results of this proposal will be important for identifying how heterotypic cell-cell interactions between the neural and vascular systems regulate neurogenesis in early brain formation. PUBLIC HEALTH RELEVANCE: Neurogenesis and angiogenesis are critical processes in development, but also play key roles in response to injury and pathological stressors, such as cerebral hemorrhage and stroke. It is important to understand not only how neurogenesis and angiogenesis are regulated in concert, but also to determine what the molecular regulators are in this process. As active neural stem cell populations are identified in the adult the possibilities for more novel therapeutic approaches and interventions become available and understanding molecular regulation of neural stem fate will be critical to success. The current proposal will address specifically a role for VEGF in regulating the survival, proliferation, and differentiation of neural stem cells in the context of the developing vasculature.