Inflammation and NG2 Cell Differentiation

描述(申请人提供)：多发性硬化症(MS)是一种脱髓鞘疾病，在美国影响着35万人，是慢性神经功能障碍的主要原因，影响成年人一生中最活跃的时期。再生髓鞘衰竭是多发性硬化症长期和原发进行性病变的特征，并与冲动传导失败和轴突病理有关。尽管再生髓鞘失败的临床效果很弱，但为什么有些病变可以有效地再生髓鞘，而另一些则不是，原因尚不清楚。表达NG2蛋白多糖的神经胶质细胞广泛存在于成熟的中枢神经系统中。最近的遗传命运图谱研究直接证明，它们不仅在发育过程中产生少突胶质细胞，而且在成熟的中枢神经系统中也产生少突胶质细胞。使用我们已经建立的新的转基因小鼠系，我们观察到，在成熟的NG2细胞中特异地缺失基本螺旋-环-螺旋转录因子Orig2会减少成年大脑中NG2细胞产生的少突胶质细胞的数量。我们还进行了高通量筛选，以确定上调寡核苷酸转录的化合物。我们将使用这些新获得的工具来检验这一假设，即在实验性自身免疫性脑脊髓炎(EAE)中，成功地重新髓鞘形成需要一个关键水平的Orig2，这是一个与MS的临床相关的啮齿动物模型。这将在以下三个特定目标中进行测试。在目标1中，我们将确定在EAE皮损中，寡核苷酸2的缺失是否会损害NG2细胞产生新的少突胶质细胞的能力。在目标2中，我们将确定新发现的增加Opol2转录的化合物是否激活了Sonic hedgehog-Gli途径或丝裂原激活的蛋白激酶途径，并测试影响不同途径的化合物促进EAE重新髓鞘形成的能力。在目标3中，我们将确定Ezh2的缺失是否会通过取消髓鞘形成所需的基因来促进重新髓鞘形成。Ezh2是多梳抑制物复合体的成员，负责组蛋白H3上赖氨酸27的甲基化。

DESCRIPTION (provided by applicant): Multiple sclerosis (MS) is a demyelinating disease that affects 350,000 people in the U.S. and is a major cause of chronic neurological deficit, affecting adults during their most active period of their lives. Remyelination failure is a characteristic of long-standing and primary progressive lesions of MS and is associated with impulse conduction failure and axonal pathology. Despite the debilitating clinical effects of remyelination failure, the reason why some lesions are effectively remyelinated while others are not remains unclear. Glial cells that express the NG2 proteoglycan (NG2 cells) exist widely throughout the mature central nervous system. Recent genetic fate mapping studies have provided direct demonstration that they generate oligodendrocytes not only during development but also in the mature central nervous system. Using new transgenic mouse lines that we have generated, we have observed that deletion of the basic helix-loop-helix transcription factor Olig2 specifically in mature NG2 cells reduces the number of oligodendrocytes that are produced from NG2 cells in the adult brain. We have also performed a high throughput screen to identify compounds that upregulate Olig2 transcription. We will use these newly acquired tools to test the hypothesis that a critical level of Olig2 is required for successful remyelination in experimental autoimmune encephalomyelitis (EAE), which is a clinically relevant rodent model of MS. This will be tested in the following three specific aims. In Aim 1, we will determine whether loss of Olig2 will compromise the ability of NG2 cells to produce new oligodendrocytes in EAE lesions. In Aim 2, we will determine whether the newly identified compounds that increase Olig2 transcription activate the Sonic hedgehog-Gli pathway or the mitogen-activated protein kinase pathway and test compounds that affect different pathways for their ability to promote remyelination in EAE. In Aim 3, we will determine whether loss of Ezh2, which is a member of the Polycomb Repressor Complex responsible for methylating lysine 27 on histone H3, will promote remyelination by derepressing genes required for myelination.