Inflammation and NG2 Cell Differentiation

描述（由申请人提供）：多发性硬化症（MS）是一种脱髓鞘疾病，在美国影响35万人，是慢性神经功能障碍的主要原因，影响成年人在他们生命中最活跃的时期。髓鞘再生衰竭是多发性硬化症长期和原发性进行性病变的特征，与冲动传导障碍和轴突病理有关。尽管髓鞘再生失败的临床效果使人衰弱，但为什么一些病变有效地髓鞘再生而另一些则没有，原因尚不清楚。表达NG2蛋白聚糖的神经胶质细胞（NG2细胞）广泛存在于成熟的中枢神经系统。最近的遗传命运定位研究直接证明，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。使用我们所产生的新的转基因小鼠系，我们观察到，在成熟的NG2细胞中特异性地缺失基本的螺旋-环-螺旋转录因子Olig2，可以减少成人大脑中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，以鉴定上调Olig2转录的化合物。我们将使用这些新获得的工具来验证实验性自身免疫性脑脊髓炎（EAE）中成功的髓鞘再生需要临界水平的Olig2这一假设，EAE是ms临床相关的啮齿动物模型。在Aim 1中，我们将确定在EAE病变中，Olig2的缺失是否会损害NG2细胞产生新少突胶质细胞的能力。在Aim 2中，我们将确定新发现的增加Olig2转录的化合物是激活Sonic hedgehog-Gli途径还是激活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中髓鞘再生的能力。在Aim 3中，我们将确定Ezh2的缺失是否会通过抑制髓鞘形成所需的基因来促进髓鞘再生。Ezh2是多梳抑制复合物的一员，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.