Müller Stephan, Chakrapani Baby P S, Schwegler Herbert, Hofmann Hans-Dieter, Kirsch Matthias
Institute of Anatomy and Cell Biology, University of Freiburg, Freiburg, Germany.
Stem Cells. 2009 Feb;27(2):431-41. doi: 10.1634/stemcells.2008-0234.
In the neurogenic areas of the adult rodent brain, neural stem cells (NSCs) proliferate and produce new neurons throughout the lifetime. This requires a permanent pool of NSCs, the size of which needs to be tightly controlled. The gp130-associated cytokines ciliary neurotrophic factor (CNTF) and leukemia inhibitory factor (LIF) have been implicated in regulating NSC self-renewal and differentiation during embryonic development and in the adult brain. To study the relevance of the two cytokines in vivo, we analyzed precursor cell proliferation and neurogenesis in the dentate gyrus of CNTF- and LIF-deficient mouse mutants. The number of radial glia-like NSCs, proliferative activity, and generation of new neurons were all reduced in CNTF(-/-) mutants but unaltered in LIF(-/-) animals. Conditional ablation of the signal transducer and activator of transcription 3 (STAT3) gene under the control of the human glial fibrillary acidic protein promoter resulted in a reduction of neurogenesis similar to that in CNTF(-/-) mice. The size of the granule cell layer was decreased in both mutants. Treatment of neurosphere cultures prepared from adult forebrain with CNTF inhibited overall proliferative activity but increased the number of NSCs as indicated by enhanced secondary neurosphere formation and upregulated expression of stem cell markers. Knockdown of STAT3 with short interfering RNA inhibited CNTF effects on neurospheres, and knockdown of suppressor of cytokine signaling 3 (SOCS3) enhanced them. Our results provide evidence that CNTF-induced STAT3 signaling is essential for the formation and/or maintenance of the neurogenic subgranular zone in the adult dentate gyrus and suggest that CNTF is required to keep the balance between NSC self-renewal and the generation of neuronal progenitors.
在成年啮齿动物大脑的神经源性区域，神经干细胞（NSCs）在整个生命周期中都能增殖并产生新的神经元。这需要一个永久性的神经干细胞库，其大小需要受到严格控制。与gp130相关的细胞因子睫状神经营养因子（CNTF）和白血病抑制因子（LIF）已被证明在胚胎发育和成年大脑中调节神经干细胞的自我更新和分化。为了研究这两种细胞因子在体内的相关性，我们分析了CNTF和LIF缺陷型小鼠突变体齿状回中前体细胞的增殖和神经发生情况。在CNTF（-/-）突变体中，放射状胶质样神经干细胞的数量、增殖活性以及新神经元的产生均减少，但在LIF（-/-）动物中未发生改变。在人类胶质纤维酸性蛋白启动子的控制下，条件性敲除信号转导和转录激活因子3（STAT3）基因导致神经发生减少，类似于CNTF（-/-）小鼠。在这两种突变体中，颗粒细胞层的大小均减小。用CNTF处理成年前脑制备的神经球培养物会抑制总体增殖活性，但会增加神经干细胞的数量，这表现为次级神经球形成增强以及干细胞标志物表达上调。用短发夹RNA敲低STAT3可抑制CNTF对神经球的作用，而敲低细胞因子信号转导抑制因子3（SOCS3）则增强了这些作用。我们的结果表明，CNTF诱导的STAT3信号对于成年齿状回神经源性颗粒下区的形成和/或维持至关重要，并提示CNTF是维持神经干细胞自我更新和神经元祖细胞产生之间平衡所必需的。
