PATTERN FORMATION IN CHICK MIDBRAIN DEVELOPMENT

描述(由申请人提供)：本研究的总体目标是 了解脑内核团形成的细胞和分子机制 产生了合适的大小、形状和神经元细胞类型的选区 在开发过程中。我们在中脑中研究这个问题，中脑是一个主要的部门 脊椎动物的大脑。在神经发生期间，雏鸡的腹侧 中脑暂时被组织成规则间隔的纵向区域 以形态和组织化学为特征的。我们的假设是，这些 被称为中脑弧的区域是一种模式机制，神经元通过这种机制 分配给不同的核命运。我们研究的目的是：(1)测试 对这一假设的预测，即中脑弧线不同于 纤维连接，以及(2)发现弧光的分子机制 是在中脑发育过程中产生的。在最初的资助期，我们 确定了最内侧的弧形产生了两个核结构， 动眼神经复合体和红核。我们还展示了一个完整的 一组中脑弧可以由异位来源的形态原引发 Sonic Hedgehog(SHH)。在提议的实验中，我们将扩展我们的测试 将弧形原核假说转移到外侧中脑，我们将解决 SHH源是否直接将弧形化为长程形态，或者 部分通过骨形态发生蛋白(BMP)中介起作用。第一 一组实验研究了外侧中脑弧的解剖学 顺行和逆行追踪方法。一项关于侧向的发现 弧形具有特征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线是特定的 原核。第二组实验测试SHH的能力，以指定 中脑弧形细胞类型直接，作为一种长程的形态发生。这些实验 将在野生型和塔尔比德(2)突变鸡胚胎中进行，使用在 体外电穿孔和组织培养方法。我们的发现是 然而，异位SHH诱导BMP基因表达的可能性增加 BMP2和BMP7可以通过SHH源参与远程信令。这个 第三组实验测试BMP信号对中脑的贡献 弧形图案。 中脑腹侧是中风和其他疾病的常见病理部位。 神经紊乱。了解它的发育生物学应该 促进治疗学研究，包括基于组织的研究 移植。更广泛地说，腹侧中脑发育为 了解大脑核团是如何形成的。对这些机制的洞察可能会表明 治疗因核消融或其他原因引起的神经性疾病的新方法 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.