PATTERN FORMATION IN CHICK MIDBRAIN DEVELOPMENT

描述（由申请人提供）：本研究的主要目标是 了解细胞和分子机制，通过这些机制， 产生适当的大小、形状和神经元细胞类型组成 在发展过程中。我们在中脑研究这个问题， 脊椎动物的大脑。在神经发生期间，鸡腹侧 中脑暂时组织成规则间隔的纵向区域 通过形态学和组织化学来区分。我们的假设是， 区域，称为中脑弧，是一种模式化机制，神经元通过这种机制， 分配到不同的核命运。本研究的目的是（1）检验 这一假设的一个预测，即中脑弧在他们的不同， 纤维连接，（2）发现电弧的分子机制， 是在中脑发育过程中产生的在最初的融资阶段，我们 确定了最内侧的弧产生两个核结构， 眼神经复合体和红核。我们还证明了一个完整的 一组中脑弧可由形态发生素的异位来源引出 Sonic Hedgehog（SHH）.在拟议的实验中，我们将扩展我们的测试， 侧中脑的弧作为原核假说，我们将解决 SHH源是否直接形成弧，作为长程形态发生素，或 部分通过骨形态发生蛋白（BMP）中介物起作用。第一 一组实验研究了中脑外侧弧的解剖结构， 顺行和逆行追踪法。一项发现， 弧具有特征性的神经元连接不仅支持 原核假说，但可以用来确定特定的弧作为具体的 原核第二组实验测试SHH指定 中脑弧细胞直接分型，作为长程形态发生原。这些实验 将在野生型和talpid（2）突变鸡胚中进行， 卵电穿孔和外植体组织培养方法。这个发现 异位SHH诱导BMP基因表达，然而， BMP 2和BMP 7可以参与SHH源的远程信令。的 第三组实验测试BMP信号对中脑的贡献 电弧图案化。 腹侧中脑是中风和其他疾病的常见病理部位。 神经系统疾病了解它的发育生物学应该 促进对治疗方法的研究，包括基于组织的治疗方法 移植更普遍地说，腹侧中脑的发育为 了解脑细胞核的形成对这些机制的深入了解可能表明， 治疗核消融术引起的神经系统疾病的新方法 断线

DESCRIPTION (provided by applicant): The broad goal of this research is to understand the cellular and molecular mechanisms by which brain nuclei of the appropriate size, shape and neuronal cell-type constituency are generated during development. We study this problem in the midbrain, a principal division of the vertebrate brain. During the period of neurogenesis, the chick ventral midbrain is transiently organized into regularly spaced, longitudinal zones distinguished by morphology and histochemistry. Our hypothesis is that these zones, called midbrain arcs, are a patterning mechanism by which neurons are allocated to different nuclear fates. The aims of our research are (1) to test a prediction of this hypothesis, that the midbrain arcs differ in their fiber-connections, and (2) to discover the molecular mechanisms by which arcs are generated during midbrain development. In the initial funding period, we established that the most medial arc gives rise to two nuclear structures, the oculomotor complex and the red nucleus. We also demonstrated that a complete set of midbrain arcs could be elicited by an ectopic source of the morphogen Sonic Hedgehog (SHH). In the proposed experiments we will extend our test of the arcs-as-pronuclei hypothesis to lateral midbrain, and we will address whether a SHH source patterns the arcs directly, as a long-range morphogen, or acts in part through bone morphogenetic protein (BMP) intermediaries. The first set of experiments studies the anatomy of the lateral midbrain arcs with anterograde and retrograde tract-tracing methods. A finding of that the lateral arcs have characteristic neuronal connections would not only support the pronuclear hypothesis, but could serve to identify particular arcs as specific pronuclei. The second set of experiments tests the competency of SHH to specify midbrain arc cell-types directly, as a long-range morphogen. These experiments will be carried out in wild-type and talpid(2) mutant chick embryos using in ovo electroporation and explant tissue culture methods. Our finding that ectopic SHH induces BMP gene expression raises, however, the possibility that BMP2 and BMP7 may participate in long-range signaling by a SHH source. The third set of experiments tests the contributions of BMP signaling to midbrain arc patterning. The ventral midbrain is a frequent site of pathology in stroke and other neurological disorders. Understanding its developmental biology should facilitate research into therapeutics, including those based on tissue transplants. More generally, ventral midbrain development provides a model for understanding how brain nuclei form. Insight into these mechanisms may suggest novel approaches to neurological disorders due to nuclear ablations or disconnections.