Regulation of glial lineage by Olig2

描述(申请人提供)：哺乳动物中枢神经系统(CNS)中表达NG2蛋白多糖的神经胶质细胞(NG2细胞)出现在胚胎晚期，并迅速扩张，均匀占据整个CNS。这些细胞不同于成熟的少突胶质细胞、星形胶质细胞或静息的分支小胶质细胞，是第四大神经胶质细胞群。培养的NG2细胞可分化为少突胶质细胞，称为少突胶质前体细胞(OPC)。使用我们新产生的NG2creBAC转基因小鼠进行的体内命运图谱研究表明，白质和背侧前脑中的NG2细胞只产生少突胶质细胞，而腹侧前脑灰质中的NG2细胞既产生少突胶质细胞又产生原浆星形胶质细胞。当NG2细胞中的基本螺旋-环-螺旋转录因子Orig2缺失时，几乎所有的NG2细胞在背侧前脑中都会分化为星形胶质细胞，而少突胶质细胞则会减少，导致髓鞘丢失。因此，NG2细胞保持了谱系可塑性，并且单个转录因子Orig2在维持NG2细胞的少突胶质细胞命运中起着关键作用。在分化程度较高的少突胶质细胞中，与早期阶段的少突胶质细胞缺失相比，其缺失并不改变新皮质GFAP的表达水平，这表明在少突胶质细胞系细胞缺失的情况下，存在一个发育窗口，即少突胶质细胞谱系细胞可以转化为星形胶质细胞。目的1验证NG2细胞在成熟为少突胶质细胞时失去其谱系可塑性并不能生成星形胶质细胞的假说，以及NG2细胞谱系可塑性的限制受表观遗传机制的调节。目的2将验证一种假设，即存在一条信号通路，维持正常脑组织NG2细胞中Orig2的表达，并阻止它们分化为星形胶质细胞。这将通过筛选小分子文库来探索，以寻找一种改变寡核苷酸转录活性的化合物。已确定的化合物将用于未来的研究，以描绘调节Orig2表达的内源信号通路。然后，该途径可以在未来的损伤修复范例中进行操纵，以促进NG2细胞分化为所需的细胞类型。 公共卫生相关性：NG2细胞代表神经胶质前体细胞群，它普遍分布在中枢神经系统的灰质和白质中。这些研究的目的是确定通过转录因子Orig2调节其谱系可塑性的机制。这些研究的结果可以用于未来的实验，在这些实验中，内源性NG2细胞的命运可以被操纵，以最大限度地促进各种类型损伤的损伤修复。

DESCRIPTION (provided by applicant): Glial cells in the mammalian central nervous system (CNS) that express the NG2 proteoglycan (NG2 cells) appear during late embryonic stages and rapidly expand to uniformly occupy the entire CNS. These cells are distinct from mature oligodendrocytes, astrocytes, or resting ramified microglia and represent a fourth major glial population. Cultured NG2 cells give rise to oligodendrocytes and are thus called oligodendrocyte precursor cells (OPCs). In vivo fate mapping studies using our newly generated NG2creBAC transgenic mice revealed that NG2 cells in the white matter and dorsal forebrain generate exclusively oligodendrocytes, while those in the gray matter of the ventral forebrain generate both oligodendrocytes and protoplasmic astrocytes. When the basic helix-loop-helix transcription factor Olig2 is deleted in NG2 cells, almost all the NG2 cells in the dorsal forebrain differentiate into astrocytes at the expense of oligodendrocytes, resulting in myelin loss. Thus, NG2 cells retain lineage plasticity, and a single transcription factor Olig2 plays a critical role in maintaining the oligodendroglial fate of NG2 cells. Deletion of Olig2 in more differentiated oligodendrocytes does not alter the level of neocortical GFAP expression, in contrast to Olig2 deletion at earlier stages, suggesting that there is a developmental window in which oligodendrocyte lineage cells can be converted into astrocytes in the absence of Olig2. Aim 1 will test the hypothesis that NG2 cells lose their lineage plasticity and become incapable of generating astrocytes as they mature into oligodendrocytes, and that restriction of lineage plasticity in NG2 cells is regulated by epigenetic mechanisms. Aim 2 will test the hypothesis that there is a signaling pathway that maintains the expression of Olig2 in NG2 cells in the normal brain and prevents them from differentiating into astrocytes. This will be explored by screening small-molecule libraries for a compound that alters Olig2 transcriptional activity. Identified compounds will be used in future studies to delineate the endogenous signaling pathways that regulate Olig2 expression. The pathway could then be manipulated in future injury repair paradigms to promote differentiation of NG2 cells into the desired cell type. PUBLIC HEALTH RELEVANCE: NG2 cells represent a glial progenitor population that is ubiquitously distributed throughout the gray and white matter of the central nervous system. The proposed studies are aimed to identify the mechanisms that regulate their lineage plasticity through the transcription factor Olig2. The results from these studies can be used in future experiments in which the fate of endogenous NG2 cells can be manipulated to maximize their contribution to lesion repair in various types injury.