Modulation of glial diversity and functional heterogeneity concerning brain activity by the lipoprotein receptor-related protein 1 (LRP1) receptor and the glycoprotein of the extracellular matrix tenascin-C

在第一个资助期间，实验室已经表明，LewisX（LeX）家族的复杂487 LeX和5750 LeX聚糖在放射状神经胶质干细胞和神经胶质祖细胞的表面上差异表达，并允许富集神经胶质亚群。细胞外基质腱生蛋白C（Tnc）和脂蛋白受体相关蛋白1（LRP 1）的糖蛋白被确定为载体蛋白。Tnc是干细胞龛基质体的组成部分，调节星形胶质细胞祖细胞的成熟。应用数字时间推移视频显微镜，我们可以表明，Tnc调节谱系树和胚胎脊髓胶质干细胞和祖细胞的细胞周期。初步数据表明，成年人的行为不同于胚胎神经胶质干细胞和祖细胞。神经干细胞微环境的功能异质性将在第二个资助期内参考Tnc得到解决。LRP 1是具有多个配体的多功能受体，包括ECM的特定组分。我们可以表明，从神经胶质干细胞和祖细胞中缺失LRP 1会损害神经发生和少突胶质细胞的生成，并有利于星形胶质细胞的分化。这种作用部分依赖于LRP 1依赖的信号转导，而不是内吞作用。选择性删除LRP 1从皮质桡导致严重的神经系统表型。从出生后第三周开始，检测到神经元兴奋性增加和癫痫发作导致死亡率增加。基于这些结果和初步数据，我们计划研究神经胶质异质性及其对神经活动的影响的机制基础上。本研究的目的如下：i）利用数字延时视频显微镜，研究胚胎和成人神经胶质干细胞和祖细胞对含Tnc微环境的不同反应的异质性; ii）监测成人CNS中487 LeX和5750 LeX聚糖的表达，并表征相应的神经胶质细胞群; iii）在GLASTCre/wtLRP 1fl/flReporterfl/fl小鼠模型中，通过条件性缺失检查LRP 1在星形胶质细胞亚群中相对于总体CNS活性的功能相关性; iv）NG 2细胞亚群中LRP 1相对于总体CNS活性的功能意义将通过NG 2Cre/wtLRP 1fl/flReporterfl/fl小鼠模型。该项目结合了遗传学，细胞生物学和生物化学方法，从发育的角度研究胶质异质性的产生及其对整体大脑活动的影响。

During the first funding period the laboratory has shown that the complex 487LeX and 5750LeX glycans of the LewisX (LeX) family are differentially expressed on the surface of radial glia stem and glial progenitor cells and permit the enrichment of glial subpopulations. The glycoprotein of the extracellular matrix tenascin C (Tnc) and the lipoprotein receptor related protein 1 (LRP1) were identified as carrier proteins. Tnc is a constituent of the stem cell niche matrisome and regulates the maturation of astrocyte progenitors. Applying digital time lapse video microscopy we could show that Tnc modulates the lineage trees and the cell cycle of embryonic spinal cord glial stem and progenitor cells. Preliminary data suggest the adult behave differently than the embryonic glial stem and progenitor cells. The functional heterogeneity of the micro milieu of neural stem cells will be addressed during the second funding period with reference to Tnc. LRP1 is a multifunctional receptor with multiple ligands, including particular components of the ECM. We could show that the deletion of LRP1 from glial stem and progenitor cells impairs neurogenesis and the generation of oligodendrocytes, and favours the differentiation of astrocytes. This effect relies partly on LRP1 dependent signal transduction, rather than on endocytosis. Selective deletion of LRP1 from cortical radial resulted in a severe neurological phenotype. Beginning with the third postnatal week increasing neuronal excitability and epileptic seizures leading to increased mortality were detected. Based on these results and preliminary data, we plan to investigate glial heterogeneity and its impact on neural activity on a mechanistic basis. The following aims will be addressed: i) the heterogeneity of embryonic and adult glial stem and progenitor cells will be explored with regard to their differential response to Tnc containing microenvironments using digital time lapse video microscopy; ii) the expression of the 487LeX and 5750LeX glycans in the adult CNS will be monitored and corresponding glial populations will be characterized; iii) the functional relevance of LRP1 in astroglial subpopulations with respect to overall CNS activity will be examined by conditional deletion in the GLASTCre/wtLRP1fl/flReporterfl/fl mouse model; iv) the functional significance of LRP1 in NG2 cell subpopulations with respect to overall CNS activity will be analysed by conditional deletion in the NG2Cre/wtLRP1fl/flReporterfl/fl mouse model. The project combines genetic, cell biological and biochemical approaches to examine the generation of glial heterogeneity and its influence on overall brain activity in a developmental perspective.