Regional specification and cell lineages of the vertebrate forebrain

本研究项目的目的是加深我们对脊椎动物前脑区域规范和组织发生的细胞和分子过程的理解。在此期间，我们在1)丘脑核的形成，2)端脑原基的早期细分，3)前神经板的细胞谱系分析，以及4)粘附连接在神经上皮分化中的作用方面取得了一些进展。我们发现，预先指定的神经元的定向迁移可能是将简单的二维丘脑雏形组织转化为三维复杂核结构的一种机制。然而，小鸡和老鼠在这一过程中似乎采用了不同的策略，这表明神经元的行为改变可能有助于产生脊椎动物物种中丘脑的组织学多样性。接下来，我们发现Wnt信号在端脑早期白质/白质下向刺猬信号的细分中起着优先作用，从而严格定义了这些区域的比例。虽然我们尝试用shRNA来鉴定实际的Wnt配体，但目前还没有成功。我们也将其向前推进，生成Six3 Cre-ER敲入小鼠系，作为分析前神经板不同部位随时间变化的细胞系的工具。我们发现，抗n -钙粘蛋白处理对粘附体连接的破坏导致神经管中的预防性神经元分化。我们的实验结果表明Notch与其配体的相互作用最有可能发生在连接结构附近。我们将继续研究其在前脑区域不同组织发生背景下神经祖细胞维持中的确切作用。

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.