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

描述(由申请人提供)：神经胶质前体细胞库持续存在于整个成人中枢神经系统。白质中风、创伤性脑损伤和复发-缓解型多发性硬化症的病变后，这一人群负责重新髓鞘形成。然而，在慢性多发性硬化症和脊髓损伤等情况下，重新髓鞘形成通常会受到抑制。抑制髓鞘形成可能有两个原因，要么是祖细胞过度维持，要么是常驻的神经胶质前体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前体细胞重新髓鞘形成的分子机制。在对成人神经胶质前体细胞进行基因组学筛选的基础上，我们发现这些细胞表达高水平的结构性激活受体酪氨酸磷酸酶RPTP？/？(PTPRZ1)。PTPRZ1可以去磷酸化连环蛋白，从而调节经典的WNT信号。Pleiotroin是RPTP？/？的内源性抑制因子，我们发现胶质前体细胞和血管内皮细胞都大量表达Pleiotroin，提示RPTP？/？依赖的信号通路既有自分泌又有旁分泌调控。在初步实验中，我们发现多营养素增加了激活的连环蛋白，类似地，RPTP？/？/PTPRZ1 shRNAi敲除增加了WNT信号下胎儿神经胶质前体细胞TCF依赖的转录。此外，我们发现RPTP？/？/PTPRZ1基因敲除增强了神经胶质前体细胞的自我更新和扩张能力，这与RPTP2/6抑制提供的？-catenin的更高可用性是一致的。在本应用程序中，我们建议使用RPTP？/？敲除结合微阵列分析以确定胎儿人神经胶质前体细胞对RPTP/？的转录反应。抑制力。通过这样做，我们希望确定RPTP的下游目标？在这些细胞中，这些细胞又可能构成调控常驻的人类神经胶质前体细胞分化命运的靶点。此外，我们还打算评估多营养素介导的RPTP是否？抑制可能被用作促进神经胶质前体细胞反应性扩增的策略，如果是这样的话，是否可以使用多营养素抑制来抑制反应性星形细胞增殖，从而增强髓鞘形成的临床治疗。因此，这些对神经胶质前体细胞信号控制的基础研究可能会为我们在与生理相关的人类细胞系统中提供更大的洞察力，了解一大类神经疾病，这些疾病共同存在反应性胶质增生和流产的重新髓鞘形成，是恢复的关键障碍。 公共卫生相关性：神经胶质前体细胞在整个成年期持续存在，这一群体负责白质中风、创伤性脑损伤和急性多发性硬化症病变等损伤后的重新髓鞘形成。然而，在慢性多发性硬化症和脊髓损伤等情况下，重新髓鞘形成通常会受到抑制。因此，本研究的目的是确定一种新的候选基因，即多营养素，以及它在体外和体内对抑制神经胶质前体细胞分化的可能作用。

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.