Fishell G, Hatten M E
Department of Pathology, College of Physicians and Surgeons, Columbia University, New York, NY 10032.
Development. 1991 Nov;113(3):755-65. doi: 10.1242/dev.113.3.755.
CNS neuronal migration is a specialized form of cell motility that sets forth the laminar structure of cortical regions of brain. To define the neuronal receptor systems in glial-guided neuronal migration, an in vitro assay was developed for mouse cerebellar granule neurons, which provides simultaneous tracking of hundreds of migrating neurons. Three general classes of receptor systems were analyzed, the neuron-glial adhesion ligand astrotactin, the neural cell adhesion molecules of the IgG superfamily, N-CAM, L1 and TAG-1, and the beta 1 subunit of the integrin family. In the absence of immune activities, migrating cerebellar granule neurons had an average in vitro migration rate of 12 microns h-1, with individual neurons exhibiting migration rates over a range between 0 to 70 microns h-1. The addition of anti-astrotactin antibodies (or Fabs) significantly reduced the mean rate of neuronal migration by sixty-one percent, resulting in eighty percent of the neurons having migration rates below 8 microns h-1. By contrast, blocking antibodies (or Fabs) against L1, N-CAM, TAG-1 or beta 1 integrin, individually or in combination, did not reduce the rate of neuronal migration. By video-enhanced contrast differential interference contrast microscopy the effects of anti-astrotactin antibodies were seen to be rapid. Within fifteen minutes of antibody application, streaming of cytoplasmic organelles into the leading process arrested, the nucleus shifted from a caudal to a central position, and the extension of filopodia and lamellopodia along the leading process ceased. Correlated video and electron microscopy suggested that the mechanism of arrest by antiastrotactin antibodies involved the failure to form new adhesion sites along the leading process and the disorganization of cytoskeletal components. These results suggest astrotactin acts as a neuronal receptor for granule neuron migration along astroglial fibers.
中枢神经系统神经元迁移是一种特殊的细胞运动形式，它形成了大脑皮质区域的分层结构。为了确定神经胶质细胞引导的神经元迁移中的神经元受体系统，我们开发了一种针对小鼠小脑颗粒神经元的体外检测方法，该方法可以同时追踪数百个迁移的神经元。我们分析了三类一般的受体系统：神经元-神经胶质细胞粘附配体astrotactin、免疫球蛋白超家族的神经细胞粘附分子N-CAM、L1和TAG-1，以及整合素家族的β1亚基。在没有免疫活性的情况下，迁移的小脑颗粒神经元在体外的平均迁移速度为每小时12微米，单个神经元的迁移速度在0至70微米/小时之间。添加抗astrotactin抗体（或Fab片段）可使神经元迁移的平均速度显著降低61%，导致80%的神经元迁移速度低于8微米/小时。相比之下，针对L1、N-CAM、TAG-1或β1整合素的阻断抗体（或Fab片段）单独或联合使用时，均不会降低神经元迁移速度。通过视频增强对比微分干涉对比显微镜观察到，抗astrotactin抗体的作用迅速。在应用抗体后的15分钟内，细胞质细胞器向突起前端的流动停止，细胞核从尾部位置移至中央位置，沿突起前端的丝状伪足和片状伪足的延伸也停止了。相关的视频和电子显微镜研究表明，抗astrotactin抗体导致迁移停止的机制涉及无法沿突起前端形成新的粘附位点以及细胞骨架成分的紊乱。这些结果表明，astrotactin作为颗粒神经元沿星形胶质纤维迁移的神经元受体发挥作用。
