Bartkowska K, Turlejski K, Grabiec M, Ghazaryan A, Yavruoyan E, Djavadian R L
Department of Molecular and Cell Neurobiology, Nencki Institute of Experimental Biology, Warsaw, Poland.
Brain Behav Evol. 2010;76(2):128-43. doi: 10.1159/000320944. Epub 2010 Nov 15.
We investigated adult neurogenesis in two species of mammals belonging to the superorder Laurasiatheria, the southern white-breasted hedgehog (order Erinaceomorpha, species Erinaceus concolor) from Armenia and the European mole (order Soricomorpha, species Talpa europaea) from Poland. Neurogenesis in the brain of these species was examined immunohistochemically, using the endogenous markers doublecortin (DCX) and Ki-67, which are highly conserved among species. We found that in both the hedgehog and mole, like in the majority of earlier investigated mammals, neurogenesis continues in the subventricular zone (SVZ) of the lateral ventricles and in the dentate gyrus (DG). In the DG of both species, DCX-expressing cells and Ki-67-labeled cells were present in the subgranular and granular layers. In the mole, a strong bundle of DCX-labeled processes, presumably axons of granule cells, was observed in the center of the hilus. Proliferating cells (expressing Ki-67) were identified in the SVZ of lateral ventricles of both species, but neuronal precursor cells (expressing DCX) were also observed in the olfactory bulb (OB). In both species, the vast majority of cells expressing DCX in the OB were granule cells with radially orientated dendrites, although some periglomerular cells surrounding the glomeruli were also labeled. In addition, this paper is the first to show DCX-labeled fibers in the anterior commissure of the hedgehog and mole. These fibers must be axons of new neurons making interhemispheric connections between the two OB or piriform (olfactory) cortices. DCX-expressing neurons were observed in the striatum and piriform cortex of both hedgehog and mole. We postulate that in both species a fraction of cells newly generated in the SVZ migrates along the rostral migratory stream to the piriform cortex. This pattern of migration resembles that of the 'second-wave neurons' generated during embryonal development of the neocortex rather than the pattern observed during development of the allocortex. In spite of the presence of glial cells alongside DCX-expressing cells, we never found colocalization of DCX protein with a glial marker (vimentin or glial fibrillary acidic protein).
我们研究了劳亚兽总目下两种哺乳动物的成年神经发生情况，分别是来自亚美尼亚的南白胸刺猬（猬形目，纯色刺猬种）和来自波兰的欧洲鼹鼠（鼩形目，欧洲鼹鼠种）。使用在物种间高度保守的内源性标记物双皮质素（DCX）和Ki-67，通过免疫组织化学方法检测了这些物种大脑中的神经发生情况。我们发现，与大多数早期研究的哺乳动物一样，刺猬和鼹鼠的侧脑室室下区（SVZ）和齿状回（DG）中都持续存在神经发生。在这两个物种的DG中，表达DCX的细胞和被Ki-67标记的细胞存在于颗粒下层和颗粒层。在鼹鼠的齿状回门中心，观察到一束粗壮的被DCX标记的突起，推测是颗粒细胞的轴突。在这两个物种的侧脑室SVZ中都鉴定出了增殖细胞（表达Ki-67），但在嗅球（OB）中也观察到了神经前体细胞（表达DCX）。在这两个物种中，OB中绝大多数表达DCX的细胞是具有放射状排列树突的颗粒细胞，不过围绕肾小球的一些球周细胞也被标记。此外，本文首次展示了刺猬和鼹鼠前连合中被DCX标记的纤维。这些纤维必定是新神经元的轴突，在两个OB或梨状（嗅觉）皮质之间建立了半球间连接。在刺猬和鼹鼠的纹状体和梨状皮质中都观察到了表达DCX的神经元。我们推测，在这两个物种中，SVZ中新生成的一部分细胞沿着吻侧迁移流迁移到梨状皮质。这种迁移模式类似于新皮质胚胎发育过程中产生的“第二波神经元”的迁移模式，而不是在旧皮质发育过程中观察到的模式。尽管在表达DCX的细胞旁边存在神经胶质细胞，但我们从未发现DCX蛋白与神经胶质标记物（波形蛋白或胶质纤维酸性蛋白）共定位。
