Mechanisms of Oligodendrocyte Fate Specification in the Developing Neocortex

项目总结 新大脑皮层对于执行我们的高级大脑功能，如认知、意识、 感知和运动控制。构成这些功能的复杂神经回路是由许多 大脑发育过程中不同类型的神经元和神经胶质细胞。这种细胞类型的多样性是如何通过 发育中的前脑中的共同神经前体细胞池是一个主要的研究焦点，但仍然有 我们对这一过程的认识存在许多根本性的差距。特别是，控制的分子机制 神经胶质细胞命运的指定和新皮质祖细胞的生成在很大程度上是未知的。长期的 这个项目的目标是了解细胞类型多样性和特异性背后的机制。 并将这一知识用于疾病大脑的治疗目的。这样做的目的是 建议阐明少突胶质细胞规范和亚型多样性的机制。 少突胶质细胞对正常的大脑发育和功能是必不可少的，它们的重要性是 在它们被破坏的疾病中强调，包括多发性硬化症和脑白质营养不良。类似 对于神经元，最近的研究已经开始揭示少突胶质细胞谱系中的多样性，这可能 反映了它们在新皮质回路中的多重功能。它的早期发展起源 少突胶质细胞的多样性尚不清楚。申请者实验室产生的初步数据表明 1)神经前体细胞的少突胶质细胞谱系在新皮质发育的早期就开始了， 在神经发生完成之前；2)在胚胎背侧前脑中向祖细胞发出的Sonic Hedgehog信号 是产生新皮质少突胶质细胞的关键；以及3)新皮质内的异质性 少突胶质细胞谱系依赖于Sonic Hedgehog信号水平的精确调节。基于这些 数据，中心假设是胚胎Shh信号将新皮质祖细胞的子集限制为 少突胶质细胞的特性和不同水平的Shh信号进一步指定了 少突胶质细胞谱系。这一假说将通过使用活体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，属于背部Ascl1血统的子代细胞将通过基因识别 命运图谱和体内克隆分析，以检验Ascl1新皮质前体细胞是 2)在第二个目标下，体内克隆分析结合剂量- 受控功能丧失方法将决定Shh信号的精确水平是否控制比率 不同亚型的少突胶质细胞系细胞。这项拟议的研究具有重要意义，因为它 有望更好地从根本上理解潜在的分子机制 少突胶质细胞规范，这是在获得特定亚型的新进展的第一步 干细胞中的少突胶质细胞用于治疗性移植以对抗脱髓鞘疾病。

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.