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

描述（由申请人提供）：神经胶质祖细胞池持续存在于整个成人中枢神经系统中。这一人群负责白色卒中、创伤性脑损伤和复发缓解型多发性硬化症病变后的髓鞘再生。然而，在慢性多发性硬化症和脊髓损伤等情况下，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。成人神经胶质祖细胞的基因组学筛选的基础上，我们发现，这些细胞表达高水平的组成型激活受体酪氨酸磷酸酶，RPTP？（PTPRZ 1）。PTPRZ 1可以使β-连环蛋白去磷酸化，从而调节经典的wnt信号传导。Pleiotrophin作为RPTP的内源性抑制剂，我们发现多效生长因子在神经胶质祖细胞和内皮细胞中大量表达，提示RPTP的自分泌和旁分泌调节控制。- 依赖信号在初步的实验中，我们发现，多效生长因子增加激活的连环蛋白，同样，RPTP？/PTPRZ 1 shRNAi敲低增加胎儿人神经胶质祖细胞的wnt信号TCF依赖性转录。此外，我们发现，RPTP？/PTPRZ 1敲低增强了神经胶质祖细胞的自我更新和扩增能力，这与RPTP 2/6抑制所提供的更大的<$-连环蛋白可用性一致。在这个应用程序中，我们建议使用RPTP <$/？基因敲除结合微阵列分析确定胎儿人神经胶质祖细胞对RPTP的转录反应？抑制作用通过这样做，我们希望确定下游目标的RPTP？/？在这些细胞中;这些反过来将包括用于调节驻留的人神经胶质祖细胞的分化命运的可能靶点。此外，我们还打算评估是否多效营养因子介导的RPTP？抑制可用作促进神经胶质祖细胞反应性扩增的策略，如果是这样，则是否可使用多效生长因子抑制来抑制反应性星形细胞增多症，从而增强髓鞘形成以用于髓鞘再生的临床治疗。因此，神经胶质祖细胞信号控制的这些基础研究可能为我们提供了很大的洞察力，在生理相关的人类细胞系统，到一个广泛的神经系统疾病，共享反应性神经胶质增生和髓鞘再生中止的关键障碍恢复。 公共卫生相关性：神经胶质祖细胞在整个成年期持续存在，并且该群体负责损伤后的髓鞘再生，例如白色卒中、创伤性脑损伤和急性多发性硬化症病变。然而，在慢性多发性硬化症和脊髓损伤等情况下，髓鞘再生通常受到抑制。因此，本建议的目的是表征一种新的候选物，多效生长因子，以及其在体外和体内抑制神经胶质祖细胞分化的可能贡献。

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.