Neuronal responses to chronic demyelination

项目摘要 少突胶质细胞是一种高度特化的神经胶质细胞类型，其使脊椎动物CNS的轴突髓鞘化， 通过跳跃式传导促进神经冲动的快速传递，并提供代谢和营养 支持轴突。该领域的一个广泛共识认为，这种少突胶质细胞的丢失 支持（如在脱髓鞘疾病如多发性硬化症中所见）直接导致轴突损失， 累积残疾然而，需要少突胶质细胞支持的直接实验证据， 轴突存活率很低。此外，关于神经元是如何 对原发性脱髓鞘损伤有反应为了更好地了解少突胶质细胞支持的丧失是否 轴突直接导致轴突损失或神经元的变化，我们将利用两个他莫昔芬诱导 Myrf基因的条件性敲除小鼠品系，该基因编码转录因子， 髓鞘形成和髓鞘维持。Myrf MyiPLP小鼠系导致少突胶质细胞损失和严重的CNS 脱髓鞘，但主要是通过募集非重组的OPC来髓鞘再生。而反观 Myrf MyiSox 10小鼠系显示出几乎完全的CNS脱髓鞘伴髓鞘再生失败，代表了 严重和慢性脱髓鞘的独特小鼠模型。 根据我们的初步数据，我们假设神经元最初即使对严重的脱髓鞘也有弹性 损伤，但他们变得容易在随后的髓鞘再生失败，炎症或 代谢挑战此外，我们还发现DLK/JNK/c-Jun轴突应激通路的激活， 慢性脱髓鞘的动物，提供了一个潜在的分子信号连接慢性脱髓鞘， 神经变性我们将在这些小鼠中使用视网膜神经节细胞（RGC）作为理想的有髓鞘神经元细胞。 1）确定髓鞘再生失败、神经炎症和代谢紊乱的相对作用。 2）建立DLK/JNK/c-Jun在介导神经元变性中的作用; 少突胶质细胞支持丧失后的变化和3）使用批量和单细胞RNA-Seq来确定 RGC对神经胶质支持丧失的反应中的转录变化，并确定是否特异性 RGC的亚组显示出对脱髓鞘的优先易感性。

PROJECT SUMMARY Oligodendrocytes are a highly specialized type of glial cell that myelinates axons of the vertebrate CNS, both promoting rapid transmission of nerve impulses via saltatory conduction and providing metabolic and trophic support for the axons. A widely held consensus view in the field holds that the loss of this oligodendrocyte support (as seen in demyelinating conditions such as multiple sclerosis) directly contributes to axonal loss and cumulative disability. Nevertheless, direct experimental evidence for oligodendrocyte support being required for axonal survival is largely lacking. In addition, there is remarkably little information available on how neurons respond to a primary demyelinating insult. To better understand whether loss of oligodendrocyte support of axons directly leads to axonal loss or neuronal changes, we will capitalize on two tamoxifen-inducible conditional knockout mouse strains for the Myrf gene, which encodes a transcription factor required for myelination and myelin maintenance. The Myrf∆iPLP mouse line leads to oligodendrocyte loss and severe CNS demyelination, but largely remyelinates through recruitment of non-recombined OPCs. In contrast, the Myrf∆iSox10 mouse line shows near complete CNS demyelination with remyelination failure, representing a unique mouse model of severe and chronic demyelination. Based on our preliminary data we hypothesize that neurons are initially resilient to even severe demyelinating insults, but that they become vulnerable to loss in the face of subsequent remyelination failure, inflammation or metabolic challenge. In addition, we have found activation of the DLK/JNK/c-Jun axonal stress pathway in chronically demyelinated animals, providing a potential molecular signal linking chronic demyelination to neurodegeneration. We will use retinal ganglion cells (RGCs) in these mice as the ideal myelinated neuronal population to: 1) determine the relative roles of remyelination failure, neuroinflammation and metabolic challenge in inducing neurodegeneration; 2) establish the role of the DLK/JNK/c-Jun in mediating neuronal changes following loss of oligodendrocyte support and 3) Use bulk and single cell RNA-Seq to determine the transcriptional changes in RGCs in response to loss of glial support and to determine whether specific subgroups of RGCs show preferential vulnerability to demyelination.