SIGNAL TRANSDUCTION PATHWAYS REGULATING NEURON DIFFERENTIATION

描述（由申请人提供）：拟议研究的长期目标是阐明哺乳动物大脑中调节神经元形态发生和连接的转录机制。我们最近发现，转录调节因子SnoN1在哺乳动物大脑神经元定位的控制中起着至关重要的作用。在出生后的大鼠幼崽中通过RNAi敲低SnoN1强烈触发体内小脑皮质中颗粒神经元的过度迁移。值得注意的是，SnoN1与转录因子FOXO 1形成复合物，FOXO 1抑制X连锁无脑畸形基因双皮质素（DCX）的转录，从而控制小脑皮质中的神经元定位。重要的是，FOXO敲低表型复制和DCX敲低抑制SnoN1敲低诱导的颗粒神经元体内过度迁移。有趣的是，SnoN1相关的选择性剪接亚型SnoN2在体内FOXO依赖性转录和神经元定位的调节中反对SnoN1的功能。这些发现将SnoN1-FOXO1复合物定义为协调神经元定位的新型细胞内在机制。我们的研究结果也提出了几个基本的问题SnoN1-FOXO1复合物在控制神经元定位的机制和生物学作用。为了解决这些问题，我们建议测试的假设，即蛋白质，特别是与SnoN1，但不SnoN2调节SnoN1-FOXO1复合物的功能在体内的转录和神经元定位。我们还将确定SnoN1-FOXO1复合物的新基因靶点，除了DCX，介导SnoN1-FOXO1复合物控制神经元定位的能力。我们还将测试的假设，SnoN1-调节神经元的定位是协调与其他关键方面的神经元发育，包括神经元分支和树突发育在体内。最后，由于DCX控制大脑皮层中的神经元迁移，我们将使用体内RNAi和互补敲除方法来测试SnoN1通路的组成部分在体内调节大脑皮层中的神经元定位的假设。这项拟议中的研究代表了一系列重要的实验，这些实验将促进我们对控制大脑中神经元定位机制的理解。由于神经元定位障碍在遗传性精神发育迟滞和癫痫疾病的发病机制中起着至关重要的作用，阐明神经元定位的机制也应该导致更好地理解这些神经发育障碍的认知和癫痫。

DESCRIPTION (provided by applicant): 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 use 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.