Rao Muddanna S, Shetty Ashok K
Department of Surgery (Division of Neurosurgery), DUMC Box 3807, Duke University Medical Centre, Durham NC 27710, USA.
Eur J Neurosci. 2004 Jan;19(2):234-46. doi: 10.1111/j.0953-816x.2003.03123.x.
Doublecortin (DCX), a microtubule-associated phosphoprotein, has been recently utilized as a marker of newly born neurons in the adult dentate gyrus (DG). Nonetheless, it is unknown whether DCX exclusively labels newly formed neurons, as certain granule cells with the phenotype of differentiated neurons express DCX. We addressed the authenticity of DCX as a marker of new neurons in the adult DG by quantifying cells that are positive for 5'-bromodeoxyuridine (BrdU), DCX and both BrdU and DCX in hippocampal tissues of adult rats treated with daily injections of BrdU for 12 consecutive days. We provide new evidence that neurons visualized with DCX immunostaining in the adult rat DG are new neurons that are predominantly born during the 12 days before euthanasia. This is confirmed by the robust expression of BrdU in 90% of DCX-positive neurons in the DG of animals injected with BrdU for 12 days. Furthermore, DCX expression is specific to newly generated healthy neurons, as virtually all DCX-positive cells express early neuronal antigens but lack antigens specific to glia, undifferentiated cells or apoptotic cells. As DCX expression is also robust in the dendrites, DCX immunocytochemistry of thicker sections facilitates quantification of the dendritic growth in newly born neurons. Thus, both absolute number and dendritic growth of new neurons that are generated in the adult DG over a 12-day period can be quantified reliably with DCX immunostaining. This could be particularly useful for analysing changes in dentate neurogenesis in human hippocampal tissues as a function of ageing or neurodegenerative diseases.
双皮质素（DCX）是一种与微管相关的磷蛋白，最近被用作成年齿状回（DG）中新生神经元的标志物。然而，尚不清楚DCX是否仅标记新形成的神经元，因为某些具有分化神经元表型的颗粒细胞也表达DCX。我们通过对连续12天每日注射溴脱氧尿苷（BrdU）的成年大鼠海马组织中对5'-溴脱氧尿苷（BrdU）、DCX以及BrdU和DCX均呈阳性的细胞进行定量，来探讨DCX作为成年DG中新神经元标志物的真实性。我们提供了新的证据，表明成年大鼠DG中通过DCX免疫染色可视化的神经元是主要在安乐死前12天内产生的新神经元。这一点在注射BrdU 12天的动物的DG中90%的DCX阳性神经元中BrdU的强烈表达得到了证实。此外，DCX表达对新产生的健康神经元具有特异性，因为几乎所有DCX阳性细胞都表达早期神经元抗原，但缺乏神经胶质细胞、未分化细胞或凋亡细胞特有的抗原。由于DCX在树突中也有强烈表达，较厚切片的DCX免疫细胞化学有助于对新生神经元的树突生长进行定量。因此，通过DCX免疫染色可以可靠地定量成年DG在12天内产生的新神经元的绝对数量和树突生长。这对于分析人类海马组织中齿状回神经发生随衰老或神经退行性疾病的变化可能特别有用。
