Zupanc Günther K H
School of Engineering and Science, Jacobs University Bremen, Bremen, Germany.
J Physiol Paris. 2008 Jul-Nov;102(4-6):357-73. doi: 10.1016/j.jphysparis.2008.10.007. Epub 2008 Oct 17.
Whereas adult neurogenesis appears to be a universal phenomenon in the vertebrate brain, enormous differences exist in neurogenic potential between "lower" and "higher" vertebrates. Studies in the gymnotiform fish Apteronotus leptorhynchus and in zebrafish have indicated that the relative number of new cells, as well as the number of neurogenic sites, are at least one, if not two, orders of magnitude larger in teleosts than in mammals. In teleosts, these neurogenic sites include brain regions homologous to the mammalian hippocampus and olfactory bulb, both of which have consistently exhibited neurogenesis in all species examined thus far. The source of the new cells in the teleostean brain are intrinsic stem cells that give rise to both glial cells and neurons. In several brain regions, the young cells migrate, guided by radial glial fibers, to specific target areas where they integrate into existing neural networks. Approximately half of the new cells survive for the rest of the fish's life, whereas the other half are eliminated through apoptotic cell death. A potential mechanism regulating development of the new cells is provided by somatic genomic alterations. The generation of new cells, together with elimination of damaged cells through apoptosis, also enables teleost fish rapid and efficient neuronal regeneration after brain injuries. Proteome analysis has identified a number of proteins potentially involved in the individual regenerative processes. Comparative analysis has suggested that differences between teleosts and mammals in the growth of muscles and sensory organs are key to explain the differences in adult neurogenesis that evolved during phylogenetic development of the two taxa.
虽然成体神经发生似乎是脊椎动物大脑中的一种普遍现象，但“低等”和“高等”脊椎动物在神经发生潜能方面存在巨大差异。对裸背电鳗和斑马鱼的研究表明，硬骨鱼中新细胞的相对数量以及神经发生位点的数量，相较于哺乳动物，至少高出一个数量级，甚至可能高出两个数量级。在硬骨鱼中，这些神经发生位点包括与哺乳动物海马体和嗅球同源的脑区，到目前为止，在所有已检测的物种中，这两个脑区都持续表现出神经发生现象。硬骨鱼大脑中新细胞的来源是内在干细胞，这些干细胞可产生神经胶质细胞和神经元。在几个脑区，年轻细胞在放射状胶质纤维的引导下迁移到特定的目标区域，并融入现有的神经网络。大约一半的新细胞会在鱼的余生中存活，而另一半则通过凋亡性细胞死亡被清除。体细胞基因组改变为新细胞的发育提供了一种潜在的调控机制。新细胞的产生，以及通过凋亡清除受损细胞，也使硬骨鱼在脑损伤后能够快速有效地进行神经元再生。蛋白质组分析已经鉴定出一些可能参与个体再生过程的蛋白质。比较分析表明，硬骨鱼和哺乳动物在肌肉和感觉器官生长方面的差异，是解释这两个分类群在系统发育过程中成年神经发生差异的关键。
