NG2-expressing cells in demyelination and remyelination: studies using new transgenic mouse models

在这个建议中，我们计划使用新的转基因小鼠品系产生脱髓鞘病变。尽管MS早期和大多数脱髓鞘动物模型表现出相当大的髓鞘再生，但在疾病晚期，髓鞘再生失败导致不可逆的轴突病理。动物模型中的再髓鞘形成已被证明是由存活的有丝分裂少突胶质祖细胞（OPC）进行的。OPC细胞表达NG2蛋白多糖：我们最近培育了一种转基因小鼠系，将EYFP基因插入内源性NG2基因的第一个外显子，当内源性启动子活跃时，在中枢神经系统中产生黄色细胞，从而可以研究NG2细胞在发育和病变中的行为。Ari Waisman实验室培育了一种小鼠品系，在给小鼠注射白喉毒素（MOG-iCre-iDTR小鼠）后，表达mog的少突胶质细胞被删除。在这个项目中，我们计划交叉这两个小鼠品系，使我们能够在标记有ng2表达细胞的小鼠中诱导脱髓鞘病变。我们将讨论NG2+祖细胞如何与脱髓鞘轴突相互作用，这些细胞的特征以及持续的脱髓鞘周期是否会导致祖细胞耗竭。通过DNA疫苗接种产生NG2特异性自身抗体，我们将研究体内针对祖细胞的免疫反应是否会因OPC的缺失或阻碍其迁移而导致髓鞘再生加剧。最后，我们将NG2零突变的纯合子NG2- EYFP小鼠与MOG-iCreiDTR杂合子小鼠杂交，以确定NG2蛋白的缺乏是否会影响髓鞘再生。

In this proposal we plan to generate demyelinating lesions using novel transgenic mouse strains. Although early phases of MS and most demyelinating animal models exhibit considerable remyelination, in later phases of the disease remyelination fails leading to irreversible axonal pathology. Remyelination in animal models has been shown to be carried out by surviving mitotic oligodendrocyte progenitor cells (OPC). OPC cells express the NG2 proteoglycan: we have recently generated a transgenic mouse line in which the EYFP gene is inserted in the first exon of the endogeneous NG2 gene, resulting in yellow cells in the CNS when the endogeneous promotor is active thus enabling study of the behaviour of NG2 cells in development as well as in lesions. The lab of Ari Waisman has generated a mouse line in which MOG-expressing oligodendrocytes are deleted after injection of mice with diptheria toxin (MOG-iCre-iDTR mice). In this project we plan to cross these two mouse strains to allow us to induce demyelinating lesions in mice in which NG2–expressing cells are labelled. We will address how NG2+ progenitor cells interact with demyelinated axons, the characteristics of these cells and whether continual cycles of demyelination result in progenitor cell depletion. By generating autoantibodies specific for NG2 via DNA vaccination, we will investigate whether mounting an immune response against the progenitor cells in vivo results in an exacerbation of remyelination due to deletion, or blockage of migration of the OPC. Lastly, we will cross the homozygous NG2- EYFP mice, which are null mutants for NG2 with the MOG-iCreiDTR heterozygous mice, to determine whether the lack of the NG2 protein affects remyelination.