Coksaygan Turhan, Magnus Tim, Cai Jingli, Mughal Mohammed, Lepore Angelo, Xue Haipeng, Fischer Itzhac, Rao Mahendra S
Gerontology Research Center, Stem Cell Biology Unit/Laboratory of Neuroscience, National Institute on Aging, National Institutes of Health, 5600 Nathan Shock Drive, Room 4E02, Baltimore, MD 21224, USA.
Exp Neurol. 2006 Feb;197(2):475-85. doi: 10.1016/j.expneurol.2005.10.030. Epub 2005 Dec 5.
Talpha-1 tubulin promoter-driven EYFP expression is seen in murine neurons born as early as E9.5. Double labeling with markers for stem cells (Sox 1, Sox 2, nestin), glial progenitors (S100beta, NG2, Olig2), and neuronal progenitors (doublecortin, betaIII-tubulin, PSA-NCAM) show that Talpha-1 tubulin expression is limited to early born neurons. BrdU uptake and double labeling with neuronal progenitor markers in vivo and in vitro show that EYFP-expressing cells are postmitotic and Talpha-1 tubulin EYFP precedes the expression of MAP-2 and NeuN, and follows the expression of PSA-NCAM, doublecortin (Dcx), and betaIII-tubulin. Talpha-1 tubulin promoter-driven EYFP expression is transient and disappears in most neurons by P0. Persistent EYFP expression is mainly limited to scattered cells in the subventricular zone (SVZ), rostral migratory stream, and hippocampus. However, there are some areas that continue to express Talpha-1 tubulin in the adult without apparent neurogenesis. The number of EYFP-expressing cells declines with age indicating that Talpha-1 tubulin accurately identifies early born postmitotic neurons throughout development but less clearly in the adult. Assessment of neurogenesis after stab wound injuries in the cortex, cerebellum and spinal cord of adult animals shows no neurogenesis in most areas with an increase in BrdU incorporation in glial and other non neuronal populations. An up-regulation of Talpha-1 tubulin can be seen in certain areas unaccompanied by new neurogenesis. Our results suggest that even if stem cells proliferate their ability to generate neurons is limited and caution is warranted in attributing increased BrdU incorporation to stem cells or cells fated to be neurons even in neurogenic areas.
早在胚胎第9.5天出生的小鼠神经元中可观察到由Tα-1微管蛋白启动子驱动的增强型黄色荧光蛋白（EYFP）表达。用干细胞标志物（Sox 1、Sox 2、巢蛋白）、神经胶质祖细胞标志物（S100β、NG2、Olig2）和神经祖细胞标志物（双皮质素、βIII-微管蛋白、多唾液酸神经细胞黏附分子）进行双重标记显示，Tα-1微管蛋白表达仅限于早期出生的神经元。体内和体外的5-溴脱氧尿嘧啶核苷（BrdU）摄取及与神经祖细胞标志物的双重标记显示，表达EYFP的细胞已完成有丝分裂，且Tα-1微管蛋白EYFP在微管相关蛋白2（MAP-2）和神经元核抗原（NeuN）表达之前出现，并在多唾液酸神经细胞黏附分子、双皮质素（Dcx）和βIII-微管蛋白表达之后出现。由Tα-1微管蛋白启动子驱动的EYFP表达是短暂的，在出生后第0天（P0）时，大多数神经元中的该表达消失。持续的EYFP表达主要局限于脑室下区（SVZ）、嘴侧迁移流和海马体中的散在细胞。然而，在成年期仍有一些区域持续表达Tα-1微管蛋白，但无明显的神经发生。表达EYFP的细胞数量随年龄增长而减少，这表明Tα-1微管蛋白在整个发育过程中能准确识别早期出生的有丝分裂后神经元，但在成年期则不太明显。对成年动物的皮质、小脑和脊髓进行刺伤损伤后的神经发生评估显示，大多数区域无神经发生，而神经胶质细胞和其他非神经元群体中的BrdU掺入增加。在某些无新神经发生的区域可观察到Tα-1微管蛋白上调。我们的结果表明，即使干细胞增殖，其生成神经元的能力也是有限的，即使在神经发生区域，将BrdU掺入增加归因于干细胞或注定成为神经元的细胞时也应谨慎。
