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，但对这些细胞在成年受损CNS中的行为仍知之甚少。公认的是，成年SVZ细胞的两种主要有丝分裂原对其行为具有非常不同的影响：FGF 2增加增殖并有利于神经发生（Kuhn et al.，1997），而EGF以神经发生为代价增加增殖（Doetsch等，2002年），但下游信号通路仍然难以捉摸。这一提议验证了以下假设，即p27 Kip 1和p53，这两个在成人SVZ中表达并经常在胶质母细胞瘤中突变的关键细胞周期调节因子，是SVZ细胞中由FGF 2和EGF激活的信号通路的下游效应子。这一假设是基于遗传学证据，来自表型表征的p27 Kip 1-/-和p53-/-小鼠，在我们的实验室进行，并表明表型之间的密切相似性p53-/-小鼠和FGF 2注射，和p27 Kip 1-/-小鼠和EGF注射。我们进一步提出，基于我们的蛋白质组学和基因分析研究的结果，这两个细胞周期基因的分子机制整合在下游信号网络，调节谱系确定和生存。因此，该提案提出了新的分子机制的作用，细胞周期分子p27 Kip 1和p53在调制不仅增殖，但也存活和谱系规范的成人祖细胞和神经干细胞居住在成人室管膜下区（SVZ）。具体目标1测试的假设，即在成人SVZ的缓慢和快速增殖的细胞的细胞周期调节是由p27 Kip 1和p53的差异调制，这些分子是FGF 2和EGF的下游。具体目标2检验了以下假设：FGF 2和EGF对成体神经发生的相反作用取决于它们对p53和p27 Kip 1的作用，p53和p27 Kip 1在影响细胞命运决定的分子网络上发挥拮抗作用。具体目标3将检验p53和p27 Kip 1在成人SVZ细胞中对凋亡途径发挥拮抗作用的假设。这些研究结果将极大地扩展我们目前对成人SVZ细胞分裂和肿瘤转化机制的认识。此外，通过解决p27 Kip和p53作为转录网络和信号通路的一部分的新的和未探索的作用，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.