Barami K, Iversen K, Furneaux H, Goldman S A
Department of Neurology and Neuroscience, New York Hospital-Cornell University Medical College, New York, New York, USA.
J Neurobiol. 1995 Sep;28(1):82-101. doi: 10.1002/neu.480280108.
The avian forebrain exhibits neurogenesis in adulthood, with neuronal production from ependymal/subependymal zone (SZ) precursor cells. To follow the commitment of newborn cells to neuronal lineage, we used their expression of the Hu family of neuronal RNA-binding proteins to identify them before their migration from the SZ. Adult canaries were injected with [3H]thymidine as a marker of DNA replication, sacrificed after varying intervals, stained for Hu, and autoradiographed. We found that Hu was not expressed by premitotic precursor cells, but rather appeared within hours in their neuronal progeny, which did not embark on parenchymal migration until 4 to 7 days later. Hu was expressed by all neurons, but not glia, both in vivo and in vitro, as determined by ultrastructural analysis as well as co-localization of Hu and cell-type selective antigens. In addition, co-staining for Hu and N-cadherin, whose expression is down-regulated on neuronal emigration from the SZ, revealed their initial co-expression by neuronal daughter cells still within the SZ. These results suggest that Hu expression may be used as a very early indicator of neuronal differentiation by SZ cells. Furthermore, the data indicate that in the adult avian brain, neuronal phenotype is established within hours of precursor mitosis, even though the neuronal daughter cells do not initiate parenchymal migration for at least 4 days thereafter, following their down-regulation of N-cadherin.
成年鸟类前脑在成年期表现出神经发生，神经元由室管膜/室下区（SZ）前体细胞产生。为了追踪新生细胞向神经元谱系的分化，我们利用它们对神经元RNA结合蛋白Hu家族的表达，在其从SZ迁移之前对它们进行识别。给成年金丝雀注射[3H]胸腺嘧啶核苷作为DNA复制的标记物，在不同时间间隔后处死，进行Hu染色并放射自显影。我们发现有丝分裂前的前体细胞不表达Hu，而是在其神经元后代中在数小时内出现Hu，而这些后代直到4至7天后才开始实质迁移。通过超微结构分析以及Hu与细胞类型选择性抗原的共定位确定，Hu在体内和体外均由所有神经元而非神经胶质细胞表达。此外，对Hu和N-钙黏着蛋白进行共染色，N-钙黏着蛋白在神经元从SZ迁出时表达下调，结果显示它们在仍位于SZ内的神经元子代细胞中最初是共表达的。这些结果表明，Hu表达可能被用作SZ细胞神经元分化的一个非常早期的指标。此外，数据表明，在成年鸟类大脑中，神经元表型在前体细胞有丝分裂后数小时内就已确立，尽管神经元子代细胞在下调N-钙黏着蛋白后至少4天内才开始实质迁移。
