Role of mPar6 Polarity in CNS Neuronal Migration

描述（由申请人提供）：年轻神经元从它们产生的位置迁移到它们建立成人大脑回路的位置是发育的关键一步。移民缺陷会导致大量的人类出生缺陷，从严重的智力迟钝到轻微的学习障碍，以及大量的癫痫。我们的实验室一直致力于了解控制迁移的基因，希望能深入了解正常发育的关键一步。我们使用小脑颗粒神经元的迁移作为模型系统来研究胶质引导的神经元迁移的分子控制。神经元极性的建立是启动神经元沿胶质向导迁移的关键步骤。筛选在颗粒神经元迁移中起作用的基因显示极性信号复合物mPar6a神经元退出循环并建立极性的高水平表达。在秀丽隐杆线虫中，一组6个PAR蛋白建立前/后不对称并控制随后的不对称细胞分裂。PAR蛋白在整个进化过程中是保守的。在初步研究中（Solecki et al, 2004），我们发现mPar6a信号复合物位于迁移的小脑颗粒神经元的中心体中，当神经元沿着胶质纤维迁移时，它协调中心体和细胞核的运动。在本研究中，我们将研究mPar6a复合物的其他组分aPKCzeta和Par3在迁移颗粒神经元极性中的作用。mPar6a在细胞分裂中的作用表明，靶向功能突变体的缺失和shRNA实验将不可行。因此，我们将使用Roger Tsien开发的一种新方法，将结合染料ReAshS的遗传标签（TC）结合到mParGq中，并使用单色激光辅助光失活中心体中的mParGa。在这些实验中，我们将产生TC-mPar6a BAC转基因小鼠，以便对颗粒细胞和皮质神经元进行研究。在最后一组实验中，我们将研究在颗粒细胞中表达的受体/配体系统，该系统与mParGa复合物、EphB配体ephrin-B1和ephrin-B2相互作用。总之，这些实验将为发育中的大脑皮层区域的神经元迁移调控提供新的信息。

DESCRIPTION (provided by applicant): The migration of young neurons from sites where they are generated into the positions where they establish the circuitry of the adult brain is a critical step in development. Defects in migration cause a host of human birth defects, ranging from severe mental retardation to subtle learning disabilities, as well as a large number of the epilepsies. Our lab has focused on understanding the genes that control migration, in the hope that insights into this key step in normal development. We use the migration of the cerebellar granule neuron as a model system to examine the molecular control of glial-guided neuronal migration. The establishment of neuronal polarity is a key step in initiating neuronal migration along the glial guide. Screens for genes that function in granule neuron migration revealed high levels of expression of the polarity signaling complex mPar6a neurons exiting the cycle and establishing polarity. In C. elegans, a set of 6 PAR proteins establish anterior/posterior asymmetries and control subsequent asymmetric cell divisions. PAR proteins are conserved throughout evolution. In Preliminary Studies (Solecki et al, 2004), we discovered that the mPar6a signaling complex is localized in the centrosome of migrating cerebellar granule neurons, where it coordinates the movement of the centrosome and the nucleus as the neuron migrates along the glial fiber. In the proposed research, we will study the other components of the mPar6a complex, aPKCzeta and Par3, in the polarity of migrating granule neurons. The role of mPar6a in cell division suggests that targeted loss of function mutants and shRNA experiments will not be feasible. We will therefore use a novel method developed by Roger Tsien to incorporate a genetic tag (TC) which binds the dye ReAshS, into mParGq and use chromophore-assisted light inactivation with a monochromatic laser to inactivate mParGa in the centrosome. For those experiments, we will generate TC-mPar6a BAC transgenic mice, enabling studies on granule cells and cortical neurons. In a final group of experiments, we will study a receptor/ligand system expressed in granule cells which interacts with the mParGa complex, the EphB ligands ephrin-B1 and ephrin-B2. Together, these experiments will provide novel information on the regulation of neuronal migration in cortical regions of developing brain.