SIGNAL TRANSDUCTION PATHWAYS REGULATING NEURON DIFFERENTIATION

摘要 拟议研究的长期目标是阐明转录调控机制。 哺乳动物大脑中神经元的形态发生和连接。我们最近发现， 转录调控因子SnoN1在哺乳动物神经元定位控制中发挥重要作用 大脑。RNAi抑制新生大鼠乳鼠SnoN1基因的表达可引发颗粒的过度迁移 活体小脑皮质中的神经元。值得注意的是，SnoN1与转录因子形成了一个复合体 Foxo1抑制X连锁无脑基因Doublecortin(DCX)的转录，从而 控制小脑皮质中神经元的定位。重要的是，FOXO击倒现象复制和DCX 基因敲除抑制SnoN1基因敲除引起的颗粒神经元在体内的过度迁移。 有趣的是，与SnoN1相关的选择性剪接异构体SnoN2与SnoN1在 FOXO依赖的转录调控和体内神经元定位。这些发现定义了 SnoN1-FOXO1复合体作为一种新的细胞内在机制来协调神经元的定位。我们的 研究结果还对SnoN1的机制和生物学作用提出了几个根本性的问题。 Foxo1复合体在控制神经元定位中的作用。为了解决这些问题，我们建议测试 一种假说认为，与SnoN1特异相关但不与SnoN1相关的蛋白质调节 SnoN1-FOXO1复合体在体内转录和神经元定位中的作用我们还将识别新的基因 除DCX外，SnoN1-FOXO1复合体的靶标，介导SnoN1-FOXO1复合体的能力 控制神经元的定位。我们还将测试SnoN1对神经元定位的调节是 与神经元发育的其他关键方面相协调，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 活体RNAi和互补基因敲除方法检验SnoN1组分的假设 在体内，通路调节大脑皮层神经元的定位。拟议的研究代表了一种 一组重要的实验，将促进我们对控制神经元的机制的理解 在大脑中的定位。由于神经元定位的紊乱在慢性阻塞性肺疾病的发病机制中起着关键作用。 遗传性精神发育迟滞和癫痫障碍，阐明支配神经元的机制 定位也应该有助于更好地理解这些认知和神经发育障碍 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.