Regional specification and cell lineages of the vertebrate forebrain

本研究的目的是加深我们对脊椎动物前脑的区域特化和组织发生所涉及的细胞和分子过程的理解。在此期间，我们在丘脑核的形成、端脑原基的早期分化、前神经板的细胞谱系分析和神经上皮细胞分化中粘附连接的作用等方面取得了一定的进展。我们发现，预先指定的神经元的定向迁移是一种可能的机制，可以转换成三维复杂的核结构的丘脑雏形的一个简单的二维组织。然而，鸡和小鼠似乎利用不同的策略，这一过程中，神经元的行为变化可能有助于产生的组织学多样性的丘脑脊椎动物物种。接下来，我们发现Wnt信号在端脑的早期苍白球/苍白球下亚区对刺猬信号起着优先作用，从而严格定义了这些区域的比例。虽然我们试图通过使用shRNA来鉴定实际的Wnt配体，但到目前为止还没有成功。我们还将其向前推进，产生Six 3 Cre-ER敲入小鼠系，作为分析前神经板不同部分随时间推移的细胞谱系的工具。我们发现，用抗N-钙粘蛋白处理破坏粘附连接导致神经管中的神经元分化。我们的实验结果表明，Notch及其配体的相互作用是最有可能发生在附近的交界结构。我们将继续研究其确切的作用，在区域不同的前脑组织发生的背景下，在维护的神经祖细胞。

The aim of this research project was to deepen our understanding of cellular and molecular processes involved in the regional specification and histogenesis of the vertebrate forebrain. In this period of support, we made some progresses on 1) nucleus formation of the thalamus, 2) early subdivision of the telencephalic primordium, 3) cell lineage analysis of the anterior neural plate, and 4) role of the adherens junction in differentiation of the neuroepithelia. We found that the directed migration of pre-specified neurons is a possible mechanism that could convert a simple two-dimensional organization of the thalamic rudiment into the three-dimensionally complicated nuclear structure. However, chick and mouse appear to utilize different strategies for this process, suggesting that behavioral change in neurons may contribute to generation of the histological diversity of thalamus among the vertebrate species. Next, we found that Wnt signaling plays a prior role for early pallial/subpallial subdivisions of the telencephalon to hedgehog signaling, thereby strictly defining the proportion of these territories. Although we tried to identify the actual Wnt ligand by using shRNA, it was not successful so far. We also pushed it forward generating Six3 Cre-ER knock-in mouse line as a tool to analyze cell lineages of different parts of the anterior neural plate over time. We found that the disruption of the adherens junction by anti-N-cadherin treatment resulted in precautious neuronal differentiation in the neural tube. Our experimental results suggest that Notch and its ligand interaction is most likely to take place in the vicinity of the junctional structure. We will continue to investigate its precise role in the maintenance of the neural progenitor cells in the context of the regionally distinct histogenesis of the forebrain.