Genetic Analysis of Cortical Development in Mice

描述(申请人提供)：神经系统形成的早期步骤是神经元和神经胶质细胞的产生，它们是所有神经回路的组成部分。在发育过程中，一些细胞退出细胞周期并分化为神经元或神经胶质细胞，而另一些细胞则重新进入细胞周期并保持祖细胞的身份。外在因素(如多肽生长因子)和内在因素(如细胞表面受体)在调节细胞增殖、命运指定和分化方面都发挥着重要作用。本提案的目的是测试这些分子在发育中的大脑皮层的神经发生和模式形成中的作用。由于认识到相对较少的基因家族在发育过程中被反复利用，信号事件的结果主要由响应细胞的类型和提供信号的发育背景决定，这一认识阻碍了此类研究。由于在许多不同的时间、地点和发育阶段重复使用一小组信号，因此很难利用遗传学来探索特定信号系统在体内特定组织中的作用。我们将在小鼠中使用条件分子遗传学技术来探索外源性信号分子及其受体在体内皮质神经元产生中的作用，并直接比较这些信号系统在发育过程中不同时间的作用。通过使用在端脑前体细胞中表达噬菌体重组酶Cre的小鼠，我们将在发育中的大脑中产生条件基因敲除或表达显性负形式的信号分子。我们将集中于骨形态发生蛋白(BMPs)和成纤维细胞生长因子(FGFs)在大脑皮层发育过程中对图案、细胞数量、表型和分化的调控作用，我们的第一个目标是解决BMP信号诱导背侧中线发育的假设。我们将在端脑指定的早期阶段单独或与Bmpr1b零突变一起进行Bmp4或其主要受体BMPR1a的条件性敲除，并分析每个突变对大脑模式和背侧中线发育的影响。第二个目的是研究成纤维细胞生长因子信号在前后部模式的形成和皮质区域的形成中的作用。我们将单独或与FGFR3的零突变一起产生成纤维细胞生长因子受体FGFR1和FGFR2的条件性敲除，以评估这些信号分子在形成皮质区域模式中的作用。我们的第三个目标是利用遗传学来探索BMP和成纤维细胞生长因子信号在皮质细胞增殖(由FGFs刺激)、神经发生(由BMPS促进)和胶质细胞产生中的相反作用。

DESCRIPTION (provided by applicant): An early step in the creation of the nervous system is the generation of neurons and glial cells, the building blocks of all neural circuits. During development, some cells exit the cell cycle and differentiate into neurons or glia, while others reenter the cell cycle and remain as progenitors. Both extrinsic factors (such as peptide growth factors) and intrinsic factors (such as cell-surface receptors) play important roles in the regulation of proliferation, fate specification, and differentiation. The goal of the present proposal is to test the roles of these molecules in neurogenesis and patterning of the developing cerebral cortex. Such studies have been hampered by the realization that relatively small numbers of gene families are utilized over and over during development, with the outcome of a signaling event determined largely by the type of the responding cell and the developmental context in which a signal is presented. Because of the repeated utilization of a small set of signals at a number of different times, places, and stages of development, it can be difficult to use genetics explore the role of a particular signaling system in a particular tissue in vivo. We will use conditional molecular genetic techniques in the mouse to explore the role of extrinsic signaling molecules and their receptors in the production of cortical neurons in vivo, and to compare directly the roles of these signaling systems at distinct times during development. By using mice that express the bacteriophage recombinase Cre in telencephalic progenitor cells, we will generate conditional knockouts or express dominant negative forms of signaling molecules in the developing brain. We will focus on the roles of Bone Morphogenetic Proteins (BMPs) and Fibroblast Growth Factors (FGFs), in the control of patterning, cell number, phenotype, and differentiation in the developing cerebral cortex, Our first aim addresses the hypothesis that BMP signaling induces the development of the dorsal midline. We will perform conditional knockouts of Bmp4 or its major receptor Bmpr1a, either alone or in combination with a null mutation in Bmpr1b, at the earliest stages of telencephalic specification and analyze the effects of each mutation on cerebral patterning and dorsal midline development. The second aim is to examine the role of FGF signaling in the development of anterior-posterior patterning and the formation of cortical areas. We will generate conditional knockouts of the FGF receptors Fgfr1 and Fgfr2, alone or in combination with a null mutation in Fgfr3, to assess the roles of these signaling molecules in patterning cortical areas, Our third aim uses genetics to explore the opposing roles of BMP and FGF signaling in cortical cell proliferation (stimulated by FGFs), neurogenesis (promoted by BMPS), and the production of glia.