Boseret Géraldine, Ball Gregory F, Balthazart Jacques
University of Liège, Center for Cellular and Molecular Neurobiology, Belgium.
J Chem Neuroanat. 2007 May;33(3):140-54. doi: 10.1016/j.jchemneu.2007.02.002. Epub 2007 Feb 16.
The protein doublecortin (DCX) is expressed in post-mitotic migrating and differentiating neurons in the developing vertebrate brain and, as a part of the microtubule machinery, is required for neuronal migration. DCX expression is generally maximal during embryonic and early post-natal life but decreases markedly and almost disappears in older animals in parallel with the major decrease or cessation of neurogenesis. In several seasonally breeding songbird species such as canaries, the volume of several song control nuclei in the brain varies seasonally such that the largest nuclei are observed in the late spring and early summer. This variation is based on changes in cell size, dendritic branching, and, in nucleus HVC, on the incorporation of neurons newly born in adulthood. Because songbirds maintain an active neurogenesis and neuronal incorporation in their telencephalon throughout their lives, we investigated here the distribution of DCX-immunoreactive (ir) structures in the brain of adult male canaries. Densely stained DCX-ir cells were found exclusively in parts of the telencephalon that are known to incorporate new neurons in adulthood, in particular the nidopallium. Within this brain region, the boundaries of the song control nucleus HVC could be clearly distinguished from surrounding structures by a higher density of DCX-ir structures. In most telencephalic areas, about two thirds of these cells displayed a uni- or bipolar fusiform morphology suggesting they were migrating neurons. The rest of the DCX-ir cells in the telencephalon were larger and had a round multipolar morphology. No such staining was found in the rest of the brain. The broad expression of DCX specifically in adult brain structures that exhibit the characteristic of active incorporation of new neurons suggests that DCX plays a key role in the migration of new neurons in the brain of adult songbirds as it presumably does during ontogeny.
双皮质素（DCX）蛋白在发育中的脊椎动物大脑中处于有丝分裂后迁移和分化的神经元中表达，作为微管机制的一部分，它是神经元迁移所必需的。DCX表达通常在胚胎期和出生后早期达到最大值，但在老年动物中显著下降并几乎消失，这与神经发生的主要减少或停止同时发生。在几种季节性繁殖的鸣禽物种中，如金丝雀，大脑中几个发声控制核的体积会随季节变化，以至于在晚春和初夏观察到最大的核。这种变化基于细胞大小、树突分支的变化，以及在HVC核中基于成年后新生神经元的并入。由于鸣禽在其一生中在端脑中维持活跃的神经发生和神经元并入，我们在此研究了成年雄性金丝雀大脑中DCX免疫反应性（ir）结构的分布。仅在成年后已知会并入新神经元的端脑部分，特别是巢皮质中发现了密集染色的DCX-ir细胞。在这个脑区中，发声控制核HVC的边界可以通过更高密度的DCX-ir结构与周围结构清楚地区分开来。在大多数端脑区域，这些细胞中约三分之二呈现单极或双极梭形形态，表明它们是正在迁移的神经元。端脑中其余的DCX-ir细胞较大，具有圆形多极形态。在大脑的其他部位未发现这种染色。DCX在成年脑结构中的广泛表达，特别是在那些表现出活跃并入新神经元特征的结构中，表明DCX在成年鸣禽大脑中对新神经元的迁移起着关键作用，就像它在个体发育过程中可能起的作用一样。
