Analysis of differentiation system in cerebral GABAergic neuron and oligodendrocyte progenitors.

gaba能神经元和少突胶质细胞在前脑发育过程中具有许多共同的特征。据报道，这两种细胞类型都起源于内侧神经节隆起并迁移到新皮层。此前有报道称，gaba能神经元祖细胞不仅表达gaba能神经元标记物，还表达少突胶质细胞祖细胞标记物，如NG2和CNP （Belachew等，2003；Aguirre等，2004；Dayer等，2005）。此外，NG2/Olig2阳性胶质祖细胞在NG2creBAC转基因小鼠（Zhu et al., 2008）和Olig2- creer敲入小鼠（Ono et al., 2008）的发育前脑中产生少突胶质细胞和星形胶质细胞。这些先前的数据提出了一种可能性，即一些gaba能神经元祖细胞在发育中的前脑中产生胶质细胞。为了验证这种可能性，我们对来自GAD67-GFP敲入小鼠大脑的GAD67-GFP阳性细胞进行了免疫组织化学、单细胞RT-PCR、单细胞微阵列分析和免疫细胞化学分析。结果发现，在gad67 - gfp阳性细胞中，神经元标记物和胶质标记物在mRNA和蛋白水平上共定位。为了进一步在体内和体外研究gaba能神经元祖细胞的细胞系，我们使用GAD67-Cre敲入小鼠和Z/EG报告小鼠。结果发现，在gad67 - gfp阳性细胞中，神经元标记物和胶质标记物在mRNA和蛋白水平上共定位。最后，为了在体内和体外研究GAD67谱系，我们使用GAD67- cre敲入小鼠和Z/EG报告小鼠。我们观察到重组后的GFP阳性细胞以gaba能神经元细胞居多，少数细胞为少突胶质细胞和星形胶质细胞。目前，我们还不能完全排除GAD67基因在小亚群胶质祖细胞细胞型化过程中出现漏表达或弱表达的可能性。

GABAergic neurons and oligodendrocyte share many characters in the forebrain development. Both cell types have been reported to originate in the medial ganglionic eminence and migrate to the neocortex. Previously, it has been reported that GABAergic neuron progenitors express not only of GABAergic neuron markers but also ones of oligodendrocytes progenitors, such as NG2 and CNP (Belachew et al., 2003 ; Aguirre et al., 2004 ; Dayer, et al., 2005). Moreover, NG2/Olig2 positive glial progenitors generate both oligodendrocyte and astrocyte in the developing forebrain using NG2creBAC transgenic mouse (Zhu et al., 2008) and Olig2-CreER knock-in mouse (Ono et al., 2008). These previous data raise a possibility that some GABAergic neuron progenitors produce glial cells in the developing forebrain. To test this possibility, here we have performed immunohistochemistry, single-cell RT-PCR, single-cell microarray analysis and immunocytochemistry analyses with glial markers in GAD67-GFP positive cells from GAD67-GFP knock-in mouse brain. As a result, we found that the neuronal markers and glial markers are co-localized in the GAD67-GFP-positive cells at mRNA and protein level. To further investigate cell lineage(s) from GABAergic neuron progenitors in vivo and in vitro, we utilized GAD67-Cre knock-in mice and Z/EG reporter mice. As a result, we found that the neuronal markers and glial markers are co-localized in the GAD67-GFP-positive cells at mRNA and protein level. Finally, to investigate GAD67 lineage in vivo and in vitro, we utilized GAD67-Cre knock-in mice and Z/EG reporter mice. We observed the most of recombined GFP positive cells were GABAergic neuron, but a few cells were oligodendrocyte and astrocyte. At present, we can not completely rule out the possibility that leaky or weak expression of GAD67 gene occur in the small subset of glial progenitors during cell-type specification.