Ventricular mixing ; its functional implication and regulatory mechanisms

在神经管切片培养中观察了室带细胞的混合行为。从E10.5 Olig 2-CreER：Z/EG双杂合胎儿制备切片，该胎儿在E9.5时用他莫昔芬处理以诱导Cre介导的重组。将切片保持长达16小时。聚焦pMN结构域中的GFP+ Olig 2谱系细胞，并每10分钟捕获图像。我们在培养切片的中线区域观察到105个GFP+细胞。其中，45个细胞在时间窗期间重新定位超过2-3行细胞。因此，近一半的观察VZ细胞进行了心室混合。我们接下来检查是否心室混合发生在脊髓和后脑在体内。Olig 2-CreER：在E9.5时用他莫昔芬处理的Z/EG双杂合子胎儿在E10.5或成年期进行分析。在成年双杂合子动物的尾侧后脑中，Olig 2谱系细胞不仅分化成舌下神经核中的躯体运动神经元，而且还分化成内脏神经元和多巴胺能神经元，后者据报道来源于更腹侧的Nkx2.2结构域。在他莫昔芬处理后24小时，一些Olig 2谱系细胞向下重新定位到Nkx2.2结构域并在VZ中表达Nkx2.2，并且有限数量向下定位到底板。此外，一些Olig 2谱系细胞的实质区域表达Phox 2b在后脑和Sim 1在脊髓; Phox 2b是一个关键的转录因子内脏神经元分化和Sim 1是一个标记转录因子V3中间神经元。目前的结果阐明，Olig 2谱系细胞通过心室混合越过域边界，并在祖细胞阶段改变其表型，可能取决于新的位置信息。

Intermixing behavior of ventricular zone (VZ) cells were examined in the slice culture of the neural tube. Slices were prepared from the E10.5 Olig2-CreER: Z/EG double heterozygous fetus that had been treated with tamoxifen at E9.5 to induce Cre-mediated recombination. Slices were maintained for up to 16 hours. GFP+ Olig2 lineage cells in the pMN domain were focused and images were captured every 10 minutes. We observed 105 GFP+ cells in the midline region of the cultured slices. Among them, 45 cells relocated over 2-3 rows of cells during the time window. Thus, nearly half of observed VZ cells underwent ventricular mixing.We next examined whether ventricular mixing occurred in the spinal cord and hindbrain in vivo. Olig2-CreER: Z/EG double heterozygous fetus treated with tamoxifen at E9.5 was analyzed at E10.5 or at adult stage. In caudal hindbrain of the adult double heterozygous animal, Olig2 lineage cells differentiated into not only somatomotor neurons in the hypoglossal nucleus but also visceromotor and serotonergic neurons, the latter of which have been reported to be derived from more ventral Nkx2.2 domain. Twenty-four hours after the tamoxifen treatment, some of Olig2 lineage cells relocated down to the Nkx2.2 domain and expressed Nkx2.2 in the VZ, and a limited number down to the floor plate. Furthermore, some of Olig2 lineage cells in the parenchymal region expressed Phox2b in the hindbrain and Sim 1 in the spinal cord; Phox2b is a critical transcription factor for visceromotor neuron differentiation and Sim 1 is a marker transcription factor for V3 interneurons. The present results elucidated that Olig2 lineage cells crossed the domain border by ventricular mixing, and change their phenotype at the progenitor stages, probably depending of the new positional information.