Molecular Mechanisms of Cerebral Cortical Patterning

描述(由申请人提供)：本研究的总体目标是 识别产生哺乳动物大脑区域图的机制 大脑皮层。创新的宫内电穿孔方法在活体小鼠体内的应用 胚胎我们发现了信号分子FGF8指定的证据 大脑前叶来源的新皮质的位置同一性 端脑。修饰内源性前部FGF8信号使区域移位 新皮质的前/后(A/P)轴，并引入了新的 FGF8的后部来源在形成过程中引起部分区域重复 异位的体感桶形场。这些研究的第一个目的是 确定FGF8是否可以充当调节图案化和 皮质区图沿A/P轴的分异。实验将会 利用宫内电穿孔操作FGF8信号，并绘制区域图 将在出生后进行分析，当新皮质区域可通过经典 连接和细胞构筑标准。第二个目标是测试 假设FGF8的前来源与第二个来源相互作用 信号蛋白，大脑皮层下摆，被认为调节大脑皮层模式 沿内侧/外侧轴。这样的互动将促进协调 沿着大脑皮层的两个主轴形成图案。第三个目标是 目的：阐明皮质原基形成模式的成纤维细胞生长因子信号机制。 使用FOF和FGF受体结构的电穿孔，我们将确定 除FGF8外，哪些成纤维细胞生长因子家族成员可能构成内源性 模式信号，哪些受体介导信号，以及成纤维细胞生长因子是否 信号作用于直接或通过继电器形成皮质原基的图案 机制。最后，我们将尝试确定 区域图案化中的成纤维细胞生长因子信号下游。特别是，为了分析 成纤维细胞生长因子8与转录因子Emx2的关系，也与A/P有关 皮质模式，我们将使用电穿孔介导的基因转移到 缺少Emx2功能的鼠标系。 几种涉及骨骼和中枢神经系统异常的人类出生缺陷 被追溯到成纤维细胞生长因子受体FGFR3的突变，它编码一种 高亲和力FGF8受体。特别是，这些突变导致到目前为止 无法解释的大脑皮层发育缺陷。建议的重点是 FGF8和FGFR3信号在早期皮质模式中的研究应得到澄清 这些缺陷是如何产生的。更广泛地说，对 大脑皮层模式的分子机制应该会为我们提供线索 导致这一部分畸形和错纹的遗传性疾病 大脑。

DESCRIPTION (provided by applicant): The broad goal of this research is to identify the mechanisms that generate the area map of the mammalian cerebral cortex. Using the innovative method of in utero electroporation in living mouse embryos we have found evidence that the signaling molecule FGF8 specifies positional identity in the neocortex from a source in the anterior telencephalon. Modifying the endogenous anterior FGF8 signal shifts areas along the anterior/posterior (A/P) axis of the neocortex, and introducing a new posterior source of FGF8 elicits a partial area duplication with the formation of ectopic somatosensory barrel fields. The first aim of these studies is to determine if FGF8 can act as a master signal that regulates the patterning and differentiation of the cortical area map along the A/P axis. Experiments will utilize in utero electroporation to manipulate FGF8 signaling, and the area map will be analyzed postnatally when neocortical areas are identifiable by classic connectional and cytoarchitectonic criteria. The second aim is to test the hypothesis that the anterior FGF8 source interacts with a second source of signaling proteins, the cortical hem, proposed to regulate cortical patterning along the medial/lateral axis. Such an interaction would promote coordination of patterning along the two major axes of the cerebral cortex. The third aim is to clarify the FGF signaling mechanism that patterns the cortical primordium. Using electroporation of FOF and FGF receptor constructs, we will determine which FGF family members, in addition to FGF8, may constitute the endogenous patterning signal, which receptors mediate the signal, and whether the FGF signal acts to pattern the cortical primordium directly or via a relay mechanism. Finally, we will attempt to identify molecular mechanisms that lie downstream of FGF signaling in area patterning. In particular, to analyze the relation between FGF8 and the transcription factor Emx2, also implicated in A/P cortical patterning, we will employ electroporation-mediated gene transfer into a mouse line lacking Emx2 function. Several human birth defects that involve skeletal and CNS abnormalities have been traced to mutations in the FGF receptor FGFR3, which encodes a high-affinity FGF8 receptor. In particular, these mutations lead to hitherto unexplained defects of cerebral cortical development. The focus of the proposed studies on FGF8 and FGFR3 signaling in early cortical patterning should clarify how these defects are generated. More generally, an understanding of the molecular mechanisms that pattern the cerebral cortex should shed light on genetic disorders that lead to malformation and mispatterning of this part of the brain.