Regulation of B-catenin by RPTPB/Z in fetal human glial progenitors

描述（由申请人提供）：一个胶质祖细胞库持续存在于整个成人中枢神经系统。这一人群在脑白质中风、外伤性脑损伤和复发-缓解型多发性硬化症病变后可发生髓鞘再生。然而，在慢性多发性硬化症和脊髓损伤等病例中，髓鞘再生通常受到抑制。髓鞘形成的抑制可能有两个原因，要么是祖细胞的过度维持，要么是常驻的胶质祖细胞分化为反应性星形胶质细胞。我们试图确定抑制神经胶质祖细胞髓鞘再生的分子机制。基于成人神经胶质祖细胞的基因组学筛选，我们发现这些细胞表达高水平的组成激活受体酪氨酸磷酸酶，RPTP¿/？(PTPRZ1)。PTPRZ1可以使连环蛋白去磷酸化，并以此调节典型的wnt信号。多营养蛋白作为内源性RPTP抑制剂我们发现，多营养蛋白在神经胶质祖细胞和内皮细胞中都大量表达，这表明RPTP有自分泌和旁分泌调控作用。-依赖信令。在初步实验中，我们发现多营养蛋白增加了活化的连环蛋白，同样地，RPTP也增加了活化的连环蛋白。/PTPRZ1 shRNAi敲低可增加胎儿人胶质祖细胞中wnt信号的tcf依赖性转录。此外，我们发现RPTP¿/？/PTPRZ1敲低可增强胶质祖细胞的自我更新和扩展能力，这与RPTP2/6抑制可提供更多的¿-catenin一致。在这个应用程序中，我们建议使用RPTP¿/？基因敲除与微阵列分析相关联，以确定胎儿人胶质祖细胞对RPTP的转录反应。抑制。通过这样做，我们期望确定RPTP的下游目标。在这些细胞中；这些反过来又可能构成调节人类胶质祖细胞分化命运的目标。此外，我们还打算评估是否多营养因子介导的RPTP ？抑制可以作为一种促进胶质祖细胞反应性扩张的策略，如果是这样，是否可以使用多营养抑制来抑制反应性星形细胞增生，从而增强髓鞘形成，用于临床治疗髓鞘再生。因此，这些神经胶质祖细胞信号控制的基础研究可以为我们提供在生理相关的人类细胞系统中，对神经系统疾病的广泛类别的深刻见解，这些疾病都具有反应性胶质增生和髓鞘再生流产，这是恢复的关键障碍。

DESCRIPTION (provided by applicant): A glial progenitor cell pool persists throughout the adult central nervous system. This population is responsible for remyelination after white matter stroke, traumatic brain injury and the lesions of relapsing- remitting multiple sclerosis. However, remyelination is often inhibited in cases such as chronic multiple sclerosis, and spinal cord injury. There could be two reasons for inhibition of myelination, either undue maintenance of the progenitor, or the differentiation of resident glial progenitors into reactive astrocytes. We seek to determine the molecular mechanism that inhibits glial progenitor cells from remyelinating. On the basis of a genomics screen of adult human glial progenitor cells, we found that these cells express high levels of a constitutively activate receptor tyrosine phosphatase, RPTP¿/? (PTPRZ1). PTPRZ1 can act to dephosphorylate ¿-catenin, and by so doing modulates canonical wnt signaling. Pleiotrophin serves as an endogenous inhibitor for RPTP¿/?, and we have found that pleiotrophin is abundantly expressed by both glial progenitors and endothelial cells, suggesting both autocrine and paracrine regulatory control of RPTP¿/? - dependent signaling. In preliminary experiments, we have found that pleiotrophin increases activated ¿-catenin, and similarly, that RPTP¿/? /PTPRZ1 shRNAi knockdown increases wnt-signaled TCF-dependent transcription by fetal human glial progenitor cells. Furthermore, we found that RPTP¿/? /PTPRZ1 knockdown potentiated both the self-renewal and expansion competence of glial progenitors, consistent with the greater availability of ¿-catenin afforded by RPTP2/6 suppression. In this application, we propose to use RPTP¿/? knock-down in association with microarray analysis to define the transcriptional response of fetal human glial progenitor cells to RPTP¿/? inhibition. By so doing, we expect to identify the downstream targets of RPTP¿/? in these cells; these in turn would comprise likely targets for modulating the differentiated fate of resident human glial progenitor cells. In addition, we also intend to assess if pleiotrophin-mediated RPTP¿/? inhibition may be used as a strategy by which to promote the reactive expansion of glial progenitor cells, and if so, whether pleiotrophin inhibition might be used to suppress reactive astrocytosis and thus enhance myelination for clinical therapies of remyelination. As such, these basic studies of signal control in glial progenitor cells may provide us great insight, in a physiologically-relevant human cell system, into a broad category of neurological diseases that share reactive gliosis and aborted remyelination as key impediments to recovery. PUBLIC HEALTH RELEVANCE: Glial progenitor cells persists throughout adulthood, and this population is responsible for remyelination after injuries such as white matter stroke, traumatic brain injury and in acute multiple sclerosis lesions. However, remyelination is often inhibited in cases such as chronic multiple sclerosis, and spinal cord injury. Therefore, this proposal aims to characterize a novel candidate, pleiotrophin, and its likely contribution to inhibiting glial progenitor differentiation in vitro and in vivo.