Chan C H, Godinho L N, Thomaidou D, Tan S S, Gulisano M, Parnavelas J G
Department of Anatomy & Developmental Biology, University College London, Gower Street, London WC1E 6BT, UK.
Cereb Cortex. 2001 Dec;11(12):1191-8. doi: 10.1093/cercor/11.12.1191.
The homeobox-containing gene, Emx1, a mouse homologue of Drosophila empty spiracles, is specifically expressed in the developing telencephalic cortex. It has been reported that Emx1 transcripts and the protein product are localized in most cells of the cerebral cortex during the process of proliferation, migration, differentiation and maturation. We provide evidence here, based on a multitude of experimental approaches in developing rats, in support of the hypothesis that the expression of this gene is restricted to pyramidal neurons. Specifically, we found that, similar to pyramidal neurons, cells expressing Emx1 are distributed in all cortical layers, except layer I. Using in situ hybridization and immunocytochemistry at the light and electron microscope levels, we have shown that the density, distribution, soma shape and ultrastructural features of these cells were identical to those of pyramidal neurons. Double-labelling experiments confirmed that the vast majority of Emx1-expressing cells also contained glutamate, a marker of pyramidal neurons. We also found that this gene is expressed by most glutamate-containing neurons in dissociated cortical cell cultures and the vast majority of cells in radially arranged clones of pyramidal cells in the cortices of chimeric mice. Thus, the homeobox gene Emx1 can be reliably used as a marker of the pyramidal cell lineage.
含同源异型框的基因Emx1是果蝇空气门的小鼠同源物，在发育中的端脑皮质中特异性表达。据报道，在增殖、迁移、分化和成熟过程中，Emx1转录本和蛋白质产物定位于大脑皮质的大多数细胞中。在此，我们基于对发育中的大鼠进行的多种实验方法，提供证据支持这一假说，即该基因的表达仅限于锥体神经元。具体而言，我们发现，与锥体神经元相似，表达Emx1的细胞分布于除第I层外的所有皮质层。通过在光学和电子显微镜水平进行原位杂交和免疫细胞化学，我们表明这些细胞的密度、分布、胞体形状和超微结构特征与锥体神经元相同。双重标记实验证实，绝大多数表达Emx1的细胞也含有谷氨酸，这是锥体神经元的一种标志物。我们还发现，在解离的皮质细胞培养物中，该基因由大多数含谷氨酸的神经元表达，在嵌合小鼠皮质中呈放射状排列的锥体细胞克隆中的绝大多数细胞也表达该基因。因此，同源异型框基因Emx1可可靠地用作锥体细胞谱系的标志物。
