SIGNAL TRANSDUCTION PATHWAYS REGULATING NEURON DIFFERENTIATION

摘要 该研究的长期目标是阐明调控转录的机制。 哺乳动物大脑中的神经元形态发生和连接。我们最近发现， 转录调节因子SnoN 1在哺乳动物神经元定位的控制中起重要作用。 个脑袋RNAi敲低出生后大鼠SnoN 1基因强烈触发颗粒过度迁移 小脑皮质的神经元。值得注意的是，SnoN 1与转录因子 FOXO 1抑制X连锁无脑畸形基因双皮质素（DCX）的转录， 控制着小脑皮层的神经元定位重要的是，FOXO敲低仿表型和DCX 敲低抑制体内SnoN 1敲低诱导的颗粒神经元过度迁移。 有趣的是，SnoN 1相关的选择性剪接异构体SnoN 2在细胞内与SnoN 1的功能相反， 体内FOXO依赖性转录和神经元定位的调节。这些发现定义了 SnoN 1-FOXO 1复合物作为一种新的细胞内在机制，协调神经元定位。我们 研究结果还提出了关于SnoN 1的机制和生物学作用的几个基本问题， FOXO 1复合物在神经元定位控制中的作用为了解决这些问题，我们建议测试 假设特异性与SnoN 1而非SnoN 2相关的蛋白质调节细胞的功能， SnoN 1-FOXO 1复合物在体内转录和神经元定位中的作用我们还将发现新的基因 SnoN 1-FOXO 1复合物的靶点，除了DCX，介导SnoN 1-FOXO 1复合物的能力， 控制神经元的定位。我们还将检验SnoN 1调节神经元定位的假设， 与神经元发育的其他关键方面协调，包括神经元分支和树突 体内发育最后，由于DCX控制着大脑皮层中的神经元迁移，我们将在 体内RNAi和互补敲除方法来测试SnoN 1的组分 信号通路调节体内大脑皮层神经元的定位。这项研究代表了一个 一组重要的实验，将促进我们对控制神经元的机制的理解， 在大脑中的位置。由于神经元定位的紊乱在脑梗死的发病机制中起着关键作用， 遗传性精神发育迟滞和癫痫疾病，阐明了控制神经元 定位也应该导致更好地理解这些神经发育障碍的认知， 癫痫

ABSTRACT The long-term goals of the proposed research are to elucidate the transcriptional mechanisms regulating neuronal morphogenesis and connectivity in the mammalian brain. We recently discovered that the transcriptional regulator SnoN1 plays an essential role in the control of neuronal positioning in the mammalian brain. Knockdown of SnoN1 by RNAi in postnatal rat pups robustly triggers the excessive migration of granule neurons in the cerebellar cortex in vivo. Remarkably, SnoN1 forms a complex with the transcription factor FOXO1 that represses transcription of the X-linked lissencephaly gene doublecortin (DCX) and thereby controls neuronal positioning in the cerebellar cortex. Importantly, FOXO knockdown phenocopies and DCX knockdown suppresses the SnoN1 knockdown-induced excessive migration of granule neurons in vivo. Interestingly, the SnoN1-related alternatively spliced isoform, SnoN2, opposes the function of SnoN1 in the regulation of FOXO-dependent transcription and neuronal positioning in vivo. These findings define the SnoN1-FOXO1 complex as a novel cell-intrinsic mechanism that orchestrates neuronal positioning. Our findings have also raised several fundamental questions on the mechanisms and biological role of the SnoN1- FOXO1 complex in the control of neuronal positioning. To address these questions, we propose to test the hypothesis that proteins that specifically associate with SnoN1 but not SnoN2 regulate the functions of the SnoN1-FOXO1 complex in transcription and neuronal positioning in vivo. We will also identify novel gene targets of the SnoN1-FOXO1 complex, besides DCX, that mediate the ability of the SnoN1-FOXO1 complex to control neuronal positioning. We will also test the hypothesis that SnoN1-regulation of neuronal positioning is coordinated with other key aspects of neuronal development including neuronal branching and dendrite development in vivo. Finally, because DCX controls neuronal migration in the cerebral cortex, we will us in vivo RNAi and a complementary knockout approach to test the hypothesis that components of the SnoN1 pathway regulate neuronal positioning in the cerebral cortex in vivo. The proposed research represents an important set of experiments that will advance our understanding of the mechanisms that control neuronal positioning in the brain. Since disturbances of neuronal positioning play a critical role in the pathogenesis of inherited mental retardation and epilepsy disorders, elucidating the mechanisms that govern neuronal positioning should also lead to a better understanding of these neurodevelopmental disorders of cognition and epilepsy.