Mechanisms of Oligodendrocyte Fate Specification in the Developing Neocortex

项目摘要 新皮层对于执行我们的高级大脑功能至关重要，如认知，意识， 感知和运动控制这些功能背后的复杂神经回路是由许多 不同类型的神经元和神经胶质在大脑发育过程中。这种细胞类型的多样性是如何从一个 发育中的前脑中神经祖细胞的共同库是主要的研究焦点，但仍然存在 我们对这一过程的认识存在许多根本性的空白。特别是，控制的分子机制 神经胶质细胞命运的特化和从新皮层祖细胞的产生在很大程度上是未探索的。长期 本项目的目标是了解细胞类型多样性和特化的机制， 大脑皮层，并将这些知识用于患病大脑的治疗目的。的目的 建议是阐明少突胶质细胞特化和亚型多样性的机制。 少突胶质细胞是大脑正常发育和功能所必需的，它们的重要性是 在它们被破坏的疾病中，包括多发性硬化症和脑白质营养不良，类似 最近的研究已经开始揭示少突胶质细胞谱系中的多样性， 反映了它们在新皮层回路中的多重功能。这种现象的早期发展起源 少突胶质细胞的多样性是未知的。在申请人的实验室中产生的初步数据表明， 1)来自神经祖细胞的少突胶质细胞谱系特化在新皮层发育早期开始， 在神经发生完成之前; 2）Sonic hedgehog信号传导到胚胎背前脑中的祖细胞 是产生新皮质少突胶质细胞的关键;和3）新皮质内的异质性 少突胶质细胞谱系依赖于Sonic hedgehog信号传导水平的精确调节。基于这些 数据，中心假设是，胚胎Shh信号限制了新皮层祖细胞的一个子集， 少突胶质细胞的身份，和不同水平的Shh信号进一步指定亚型内的命运。 少突胶质细胞谱系。这一假设将通过使用体内技术追求两个特定目标来检验 在小鼠中：1）在第一个目标下，将通过遗传学方法鉴定属于背侧Ascl 1谱系的子细胞。 命运定位和体内克隆分析，以检验Ascl 1+新皮质祖细胞是 2）在第二个目的下，体内克隆分析与剂量限制相结合， 受控的功能丧失方法将确定Shh信号传导的精确水平是否控制比率， 不同亚型的少突胶质细胞谱系细胞。这项拟议的研究意义重大，因为它是 有望提供一个更好的基本了解的分子机制， 少突胶质细胞的特化，这是朝着新的进展，在推导特定亚型的第一步， 用于治疗性移植以对抗脱髓鞘疾病的干细胞的少突胶质细胞。

PROJECT SUMMARY The neocortex is crucial for execution of our higher order brain functions such as cognition, consciousness, perception and motor control. The complex neural circuits that underlie these functions are built from many different types of neurons and glia during brain development. How this cell type diversity is achieved from a common pool of neural progenitors in the developing forebrain is a major research focus, but there are still many fundamental gaps in our knowledge of this process. In particular, the molecular mechanisms that control glial cell fate specification and generation from neocortical progenitors are largely unexplored. The long-term goal of this project is to understand the mechanisms underlying cell type diversity and specification in the cerebral cortex and to use this knowledge for therapeutic purposes in the diseased brain. The objective of this proposal is to elucidate the mechanisms underlying oligodendrocyte specification and subtype diversity. Oligodendrocytes are essential for normal brain development and function, and their importance is underscored in diseases in which they are disrupted, including multiple sclerosis and leukodystrophies. Similar to neurons, recent studies have started to uncover diversity within the oligodendrocyte lineage that likely reflects their multiple functions in the neocortical circuitry. The early developmental origins of this oligodendrocyte diversity are not known. Preliminary data produced in the applicants' laboratory indicates that 1) oligodendrocyte lineage specification from neural progenitors begins early in neocortical development, before neurogenesis is complete; 2) Sonic hedgehog signaling to progenitors in the embryonic dorsal forebrain is critical for generating neocortical oligodendrocytes; and 3) heterogeneity within the neocortical oligodendrocyte lineage depends on precise regulation of Sonic hedgehog signaling levels. Based on these data, the central hypothesis is that embryonic Shh signaling restricts a subset of neocortical progenitors to oligodendrocyte identities, and differing levels of Shh signaling further specifies subtype fate within the oligodendrocyte lineage. This hypothesis will be tested by pursuing two specific aims using in vivo techniques in mice: 1) Under the first aim, daughter cells belonging to the dorsal Ascl1 lineage will be identified by genetic fate-mapping and in vivo clonal analysis, to test the hypothesis that Ascl1+ neocortical progenitors are oligodendrocyte-fate restricted; 2) Under the second aim, in vivo clonal analyses in combination with dose- controlled loss-of-function approaches will determine whether precise levels of Shh signaling control the ratio of different subtypes of oligodendrocyte-lineage cells. The proposed research is significant because it is expected to provide a better fundamental understanding of the molecular mechanisms underlying oligodendrocyte specification, and it is the first step toward new advances in deriving specific subtypes of oligodendrocytes from stem cells for therapeutic transplantation to combat demyelinating disorders.