Circadian mechanisms of myelination

髓鞘-包裹轴突的结构-是有效转导电信号和代谢的组成部分。 神经元的支持。髓磷脂缺乏通常在广泛的脑部疾病中被发现-从 神经发育到神经退行性变-涉及髓鞘形成障碍，作为一个突出的，但往往被低估， 许多神经系统疾病的特征。类似的髓磷脂缺乏会导致注意力、记忆力、学习能力的下降， 社会行为和运动功能。为了最终了解髓鞘形成是如何失败的， 大脑疾病，我们首先必须有一个全面的了解机制驱动的扩散， 髓鞘形成前体细胞的维持。在出生前和出生后的发育髓鞘形成， 成年期神经元活性依赖性适应性髓鞘形成均依赖于少突胶质前体细胞 （OPCs）及其后代，髓鞘形成少突胶质细胞。在确定机制方面， 在这两种类型的髓鞘形成过程中介导OPC动力学，并揭示它们在定义和完善 发育和疾病中的回路和行为。OPC是大脑中最丰富的有丝分裂细胞， 在给定的时间内，所有分裂细胞的90%是OPC。基于已发表的工作，表明昼夜节律（~24小时） 由主要的昼夜节律分子调节因子Bmal 1驱动的系统调节许多神经细胞的细胞增殖， 前体细胞和干细胞群体以及我们的初步数据证实了Bmal 1在OPC动力学中的必要性， 我们的目的是研究昼夜节律系统如何调节OPCs和随之而来的髓鞘形成。除了 髓鞘形成障碍、昼夜节律相移和生物钟基因（如BMAL 1）的多态性已经被发现， 在患有自闭症、注意力缺陷/多动症、多发性硬化症和阿尔茨海默氏症的个体中记录 疾病，在这些疾病的病理生理学与昼夜节律机制的中断。我们将这种昼夜节律 髓鞘形成细胞在发育过程中的破坏将为广泛的脑病理学奠定基础。 在这个提议中，我们的目标是提升目前对髓鞘形成的生物学理解。拟议的工作将 研究昼夜节律系统如何通过1）两种不同的，但 靶向OPC中Bmal 1敲低以探测发育髓鞘形成的互补遗传小鼠模型2） 环境时间破坏性慢性时差（CJL）模型在发育髓鞘形成中的应用，以及3） 神经元活性诱导的适应性髓鞘形成的昼夜变化。我们的初步数据表明基因敲除 在胚胎和出生后发育过程中，OPC中Bmal 1驱动的昼夜节律钟的下降导致 1）OPC密度的降低，2）OPC增殖，3）髓鞘形成，和4）髓鞘相关行为。一 全面了解昼夜节律调节与OPC维持和髓鞘形成之间的相互作用 它不仅将提供大脑健康机制的信息，还将建立对潜在治疗策略的见解 靶向许多脑疾病中的髓鞘特异性昼夜节律调节过程。

Myelin—the structure that encapsulates axons—is integral to efficient transduction of electrical signals and metabolic support of neurons. Myelin deficits have been commonly identified in a wide range of brain disorders—from neurodevelopmental to neurodegenerative—implicating dysmyelination as a prominent, but often underappreciated, feature of many neurological disorders. Similar myelin deficiencies cause decrements in attention, memory, learning, social behaviors, and motor function in preclinical models. To ultimately understand how myelination fails in these brain disorders, we first must have a comprehensive understanding of the mechanisms driving the proliferation and maintenance of myelin-forming precursor cells. Developmental myelination during pre- and post-natal life and neuronal activity-dependent adaptive myelination in adulthood both depend on oligodendrocyte precursor cells (OPCs) and their progeny, myelin-forming oligodendrocytes. There remains an unmet need to define the mechanisms mediating OPC dynamics during these two types of myelination and to reveal their roles in defining and refining circuits and behavior in development and disease. The OPC is the most abundantly mitotic cell in the brain with 70- 90% of all dividing cells at a given time being OPCs. Based on published work showing that the circadian (~24 hour) system—driven by the principal circadian molecular regulator Bmal1—regulates cell proliferation of numerous neural precursor and stem cell populations and our preliminary data confirming the necessity of Bmal1 in OPC dynamics, we aim to investigate how the circadian system regulates OPCs and consequent myelination. In addition to dysmyelination, circadian phase-shifts and polymorphisms in circadian clock genes like BMAL1 have been documented in individuals with autism, attention deficit/hyperactivity disorder, multiple sclerosis, and Alzheimer’s disease, linking disruptions in circadian machinery with pathophysiology in these disorders. We posit that circadian disruption of myelin-forming cells during development will lay the foundation for a broad range of brain pathologies. In this proposal, we aim to elevate the current biological understanding of myelination. The proposed work will investigate how the circadian system regulates myelination through 1) the development of two distinct but complimentary genetic mouse models targeting Bmal1 knock down in OPCs to probe developmental myelination 2) application of the environmental chronodisruptive chronic jet lag (CJL) model to developmental myelination, and 3) diurnal changes in neuronal activity-induced adaptive myelination. Our preliminary data establish that genetic knock down of the Bmal1-driven circadian clock in OPCs during embryonic and post-natal development results in a reduction in 1) OPC density, 2) OPC proliferation, 3) myelination, and 4) myelin-associated behaviors. A comprehensive understanding of the interplay between circadian modulation and OPC maintenance and myelination will not only inform on mechanisms of brain health but will also establish insights into potential therapeutic strategies targeting myelin-specific circadian regulatory processes in numerous brain disorders.