Regulation of glial lineage by Olig2

描述（由申请人提供）：哺乳动物中枢神经系统（CNS）中表达NG2蛋白聚糖（NG2细胞）的胶质细胞在胚胎后期出现，并迅速扩张并均匀地占据整个中枢神经系统。这些细胞不同于成熟的少突胶质细胞、星形胶质细胞或静止的分枝小胶质细胞，它们代表了第四种主要的胶质细胞群。培养的NG2细胞产生少突胶质细胞，因此被称为少突胶质细胞前体细胞（OPCs）。利用NG2creBAC转基因小鼠进行的体内命运图谱研究显示，NG2细胞在白质和前脑背侧只产生少突胶质细胞，而在前脑腹侧灰质中既产生少突胶质细胞，也产生原生质星形胶质细胞。当NG2细胞中基本的螺旋-环-螺旋转录因子Olig2缺失时，前脑背侧的NG2细胞几乎全部以少突胶质细胞为代价分化为星形胶质细胞，导致髓磷脂损失。因此，NG2细胞保持谱系可塑性，单一转录因子Olig2在维持NG2细胞的少突胶质命运中起着关键作用。在分化程度较高的少突胶质细胞中，Olig2缺失不会改变新皮质GFAP的表达水平，这与早期阶段的Olig2缺失不同，这表明在缺乏Olig2的情况下，少突胶质细胞谱系细胞可以转化为星形胶质细胞。目的1将验证NG2细胞在向少突胶质细胞成熟的过程中失去谱系可塑性并不能产生星形胶质细胞的假设，以及NG2细胞谱系可塑性的限制受到表观遗传机制的调节。Aim 2将验证一个假设，即存在一种信号通路维持正常大脑NG2细胞中Olig2的表达，并阻止其分化为星形胶质细胞。这将通过筛选小分子文库来探索改变Olig2转录活性的化合物。鉴定的化合物将在未来的研究中用于描述调节Olig2表达的内源性信号通路。然后，在未来的损伤修复范式中，可以操纵该途径，以促进NG2细胞分化为所需的细胞类型。

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.