大脑皮层神经元放射状迁移导向机制的新发现

神经系统由规则的细胞群落和精细的神经回路组成，这些精巧的构造对于脑的各项高级功能是至关重要的。作为神经系统高级中枢的大脑皮层长期以来都是研究脑结构发育机理的重要模式系统。成年哺乳动物的大脑皮层神经元排列成典型的板层结构（1aminar structure），每一层神经元都具有特定的输入和输出神经联系。

New Mechanism of Guiding Radial Migration of Cortical Neurons

Postmitotic neurons in the developing cortex mi- grate along radial glial fibers to their proper location in the cortical plate and form the layered structure. Here we report that the radial migration of rat layer Ⅱ/Ⅲ cortical neurons requires guidance by the extracellular diffusible factor Semaphorin-3A （Sema3A）. This factor is expressed in a descending gradient across the cortical layers, whereas its receptor neuropilin-1 （ NP1 ） is highly expressed in migrating neurons. Downregulation or conditional knockout of NP1 in newborn cortical neurons impedes their radial migration by disrupting their radial orientation during migration without altering their cell fate. Studies in cultured cortical slices further show that the endogenous gradient of Sema3A is required for the proper migration of newborn neurons. In addition,transwell chemotaxis assays show that isolated newborn neurons are attracted by Sema3A. Thus, Sema3A may function as a chemoattractive guidance signal for the radial migration of newborn cortical neurons toward upper layers.