Role of cell cycle inhibitors in adult neural stem cells

描述（由申请人提供）：虽然干细胞疗法已被提出用于修复，但对于这些细胞在成人受损中枢神经系统中的行为知之甚少。人们普遍认为，成年SVZ细胞的两种主要有丝分裂原对其行为有非常不同的影响：FGF2增加增殖并有利于神经发生（Kuhn et al., 1997），而EGF增加增殖以牺牲神经发生为代价（Doetsch et al., 2002），但下游信号通路仍然难以确定。该研究证实了p27Kip1和p53是SVZ细胞中FGF2和EGF激活的信号通路的下游效应器。p27Kip1和p53是成年SVZ细胞中表达的两个关键的细胞周期调节因子，经常在胶质母细胞瘤中发生突变。这一假设是基于我们实验室对p27Kip1-/-和p53-/-小鼠的表型特征进行的遗传证据，表明p53-/-小鼠和FGF2注射的表型非常相似，p27Kip1-/-小鼠和EGF注射的表型非常相似。基于我们的蛋白质组学和基因分析研究结果，我们进一步提出了一种分子机制，将这两个细胞周期基因整合到下游信号网络中，调节谱系决定和生存。因此，本研究提出了细胞周期分子p27Kip1和p53在调节成人祖细胞和成人心室下区（SVZ）神经干细胞增殖、存活和谱系规范中的作用的新分子机制。特异性目的1验证了成人SVZ中缓慢和快速增殖细胞的细胞周期调节是由p27Kip1和p53差异调节的，这些分子位于FGF2和EGF的下游。特异性目的2验证了FGF2和EGF对成人神经发生的相反作用取决于它们对p53和p27Kip1的作用的假设，p53和p27Kip1在影响细胞命运决定的分子网络中起拮抗作用。特异性目的3将验证p53和p27Kip1在成年SVZ细胞凋亡通路中发挥拮抗作用的假设。这些研究结果将大大扩展我们目前对成年SVZ细胞的细胞分裂和肿瘤转化机制的认识。此外，通过解决p27Kip和p53作为转录网络和信号通路的一部分的新的和未被探索的角色，它们也将显著影响其他几个领域，包括发育神经生物学和临床神经生物学。

DESCRIPTION (provided by applicant): Although stem cell therapy has been proposed for repair, still relatively little is known about the behavior of these cells in the adult injured CNS. It is well accepted that two major mitogens for adult SVZ cells have very different effects on their behavior: FGF2 increases proliferation and favors neurogenesis (Kuhn et al., 1997), while EGF increases proliferation at the expenses of neurogenesis (Doetsch et al., 2002), but the downstream signaling pathways remain elusive. This proposal tests the hypothesis that p27Kip1 and p53, two crucial cell cycle regulators which are expressed in the adult SVZ and often mutated in glioblastomas, are downstream effectors of signaling pathways activated by FGF2 and EGF in SVZ cells. This hypothesis is based on genetic evidence derived from the phenotypic characterization of p27Kip1-/- and in p53-/- mice, conducted in our laboratory and indicating a close similarity between the phenotype of p53-/- mice and FGF2 injection, and that of p27Kip1-/- mice and EGF injection. We further propose, based on the results of our proteomic and gene profiling studies, a molecular mechanism integrating these two cell cycle genes within downstream signaling networks that modulate lineage determination and survival. Therefore, this proposal addresses novel molecular mechanisms for the role of the cell cycle molecules p27Kip1 and p53 in modulating not only proliferation, but also survival and lineage specification of adult progenitors and neural stem cells residing in the adult subventricular zone (SVZ). Specific aim 1 tests the hypothesis that cell cycle regulation of slow and fast-proliferating cells in the adult SVZ is differentially modulated by p27Kip1 and p53 and that these molecules are downstream of FGF2 and EGF. Specific aim 2 tests the hypothesis that the opposing role of FGF2 and EGF on adult neurogenesis is dependent on their effect on p53 and p27Kip1 which play antagonistic roles on molecular networks affecting cell fate determination. Specific aim 3 will test the hypothesis that p53 and p27Kip1 exert antagonistic functions on apoptotic pathways in adult SVZ cells. The results of the proposed studies will significantly extend our current knowledge on the mechanisms of cell division and neoplastic transformation of adult SVZ cells. In addition, by addressing novel and unexplored roles for p27Kip and p53 as part of transcriptional networks and signaling pathways, they will also significantly impact several other fields, including developmental neurobiology and clinical neurobiology.