Patterning of late-acting germinal zones in the vertebrate CNS

描述（由申请人提供）：神经科学和再生医学的一个基本挑战是了解特定的神经元亚型如何在正确的数量、规定的时间和精确的位置出现。为协调这些事件而制定的项目已经开始被定义，例如，通过对早期脊髓神经管的研究；部分原因是由于物理和分子的可及性，以及相对简单的解剖结构——新生的神经元通常径向移动短距离，保持原始的DV/AP关系。生发区通过切向迁移模式将神经元群分布到遥远和不同的位置，而生发区是如何调控这些事件的，这通常是在发育后期进行的，目前尚不清楚。然而，这些生发区对大脑中神经元的多样性做出了重大贡献，鉴于其独特的性质和妊娠后期神经组织的独特环境，必须以新的方式来实现。本研究旨在通过对后脑（下）菱形唇（LRL）的研究来填补这一知识空白的关键方面，LRL是一个迟起作用的重要生发区，现在可以通过分子遗传学手段获得。LRL产生多种功能关键的脑干细胞类型，其中许多受到发育和退行性疾病的影响。我们提供的证据表明：(1)这种产生的细胞类型的多样性反映在LRL精确定义的分子亚区域化上——LRL不是同质的，而是由DV和AP基因表达微域组成，预测后代神经元的身份；(2)转录因子Pax6调节这种分子亚区域化的各个方面，确保产生正确比例的后代谱系；(3)典型的腹侧化形态原Sonic hedgehog （Shh）在背侧的后脑脉络丛上皮中表达，这是一个已知的背侧组织中心，本身是一个LRL谱系。这种先前被排除的模式分子，如Pax6和Shh，可能代表了一种普遍的策略，通过这种策略，一个迟起作用的生发区可以继续产生独特的祖细胞状态和命运。我们的目标是双重的：通过将高分辨率的DV:AP坐标连接到后来生成的细胞命运来扩展我们的LRL命运图（目标1）；在这张图上标出调节这种分子组织的分子活动，从而产生特定的细胞类型；例如，我们将探索Pax6和Shh的新作用（目标2和3）。

DESCRIPTION (provided by applicant): A fundamental challenge in neuroscience and regenerative medicine is to understand how specific neuron subtypes arise in correct number, at defined times, and target to precise locations. Programs enacted to coordinate such events have begun to be defined, for example, through studies of early-stage spinal neural tube; in part due to physical and molecular accessibility, and relatively simple anatomy--newly born neurons typically move short distances radially, maintaining originating DV/AP relationships. Less clear is how such events are regulated in germinal zones that distribute neuron cohorts to distant and varied locations through tangential migration modes, and which typically do so at later developmental stages. Yet such germinal zones contribute substantially to neuron diversity in the brain and must do so in novel ways given their unique properties and the distinct milieu of late-gestation neural tissue. This proposal seeks to fill key aspects of this knowledge gap through studies of the hindbrain (lower) rhombic lip (LRL), a late-acting and essential germinal zone now accessible by molecular genetic means. Diverse and functionally critical brainstem cell types arise from the LRL, many subject to developmental and degenerative disorders. We provide evidence that (1) this diversity in produced cell types is reflected in a precisely defined molecular sub-regionalization of the LRL - the LRL is not homogeneous, but rather comprised of DV and AP gene expression microdomains predictive of progeny neuron identity; (2) the transcription factor Pax6 modulates aspects of this molecular sub-regionalization, ensuring that correct proportions of descendant lineages are produced; and (3) the archetypal ventralizing morphogen, Sonic hedgehog (Shh), is expressed in the dorsally situated hindbrain choroid plexus epithelium, a known dorsal organizing center and itself a LRL lineage. Such co-opting of previously excluded patterning molecules, such as Pax6 and Shh, may represent a general strategy by which a late-acting germinal zone may continue generating unique progenitor cell states and fates. Our goal is to two-fold: Extend our LRL fate map by linking highly resolved DV:AP coordinates to later-generated cell fates (Aim 1); place on this map the action of molecules which regulate this molecular organization and thus production of specific cell types; for example, we will explore novel roles for Pax6 and Shh (Aims 2 & 3).