Kriegstein Arnold R
Department of Neurology, University of California, San Francisco, San Francisco, California 94143, USA.
Epilepsia. 2005;46 Suppl 7:15-21. doi: 10.1111/j.1528-1167.2005.00304.x.
Our knowledge of the proliferation, migration, and differentiation of neurons has changed dramatically over the last 10 years. Whereas traditionally it was thought that glial and neuronal cells were separate cell lines with different lineages, we now know that this is not true. Radial glia are a type of neural stem cell that generate excitatory pyramidal neurons directly through asymmetric cell division in the ventricular zone (VZ) of the telencephalon and indirectly through the symmetric division of daughter intermediate precursor cells that divide in the subventricular zone (SVZ). Moreover, pyramidal neurons, once thought to migrate only along radial guide fibers to the developing layers of the cortex, have been shown to proceed through four distinct stages of migration during which they change shape, direction, and speed. Gamma-aminobutyric acid (GABAergic) inhibitory interneurons, on the other hand, are generated not in the cortex, but in the medial ganglionic eminence and migrate tangentially to their final cortical destinations. Evidence suggests that GABA activation may play a role in coordinating the generation and migration of both pyramidal and interneuron populations. At the end of neurogenesis, radial glial cells translocate to the cortex and transform into astrocytes. Although they do not actively divide in the adult brain, astrocytes may retain the potential to generate new neurons. These new findings have increased our understanding of the mechanisms underlying certain developmental disorders and, in doing so, reveal potentially useful modes of therapeutic intervention.
在过去十年中，我们对神经元的增殖、迁移和分化的认识发生了巨大变化。传统上认为神经胶质细胞和神经元细胞是具有不同谱系的独立细胞系，但现在我们知道并非如此。放射状胶质细胞是一种神经干细胞，它通过端脑脑室区（VZ）的不对称细胞分裂直接产生兴奋性锥体神经元，并通过在脑室下区（SVZ）分裂的子代中间前体细胞的对称分裂间接产生兴奋性锥体神经元。此外，锥体神经元曾被认为仅沿着放射状引导纤维迁移到皮质的发育层，但现已证明它们在迁移过程中会经历四个不同阶段，在此期间它们会改变形状、方向和速度。另一方面，γ-氨基丁酸（GABA能）抑制性中间神经元并非在皮质中产生，而是在内侧神经节隆起中产生，并沿切线方向迁移到它们最终的皮质目的地。有证据表明，GABA激活可能在协调锥体神经元和中间神经元群体的产生和迁移中发挥作用。在神经发生结束时，放射状胶质细胞迁移到皮质并转化为星形胶质细胞。虽然它们在成人大脑中不进行活跃分裂，但星形胶质细胞可能保留产生新神经元的潜力。这些新发现增进了我们对某些发育障碍潜在机制的理解，从而揭示了可能有用的治疗干预模式。
