The floor plate (FP) is a critical signaling center for the development of neural tube and body axis, and is localized at the ventral midline of the neural tube. Multiple types of neurons are present in the floor plate, while the distribution pattern of these neuronal cells remains unclear. By using transgenic zebrafish lines that specifically label different neuronal cells, we investigated the distribution pattern of these neurons in the floor plate region. Our results showed that foxj1a, sox2, clusterin and gfap genes were expressed in the medial floor plate (MFP), consisting of a single row of cells. The cerebrospinal fluid-contacting neurons (CSF-cNs), also named as Kolmer-Agduhr interneurons (KA' and KA" neurons), were located on the lateral sides of MFP. The foxj1a and pkd2l1 genes were expressed in the KA" neurons, which were located to the ventral terminal gap of wedge-shaped MFP cells. The neighboring KA" neurons were separated by neurons expressing Gfap, Olig2 or Sox2. In contrast, the KA' neurons were positive for Foxj1a +/Pkd2l1+/Olig2+, and were localized to the dorsal side of KA" neurons. Similarly, the Sox2 or Olig2 expressing neurons were intermingled with KA' neurons along the anterior-posterior axis in these regions. Further pharmaceutical treatment demonstrated that interference of Notch signaling resulted in the abnormal distribution of floor plate neurons together with strong dorsal body curvature at 3 days post fertilization in the zebrafish larvae. Our data showed the gene expression patterns and relative positions of the floor plate neurons; and suggested a potential role of Notch signaling during floor plate development.
神经底板(floor plate, FP)位于神经管腹侧中线区,存在多种神经细胞类型,是调控神经管分化及维持体轴生长的重要信号中心。目前,对神经底板处神经元细胞的类型及分布研究并不深入。本研究以斑马鱼(Danio rerio)为模式动物,结合多种神经细胞的转基因品系,分析了斑马鱼幼鱼中神经底板细胞群的排列图式。研究发现,foxj1a、sox2、clusterin和gfap等多个基因在内侧中央底板(medial floor plate, MFP)单排细胞中表达。Kolmer-Agduhr神经元KAʼ与KA”又称为脑脊液接触神经元,定位在MFP附近,其中KA”神经元表达foxj1a和pkd2l1基因,与表达Gfap蛋白、Olig2蛋白或Sox2蛋白的阳性细胞间隔性插入MFP细胞腹侧间隙中。KAʼ神经元位于KA”背侧,表达foxj1a、pkd2l1和olig2基因,并与Sox2+或Olig2+阳性细胞间隔分布于MFP细胞胞体的两侧。药物处理实验结果表明：抑制Notch信号影响神经底板的发育,导致神经底板细胞排布异常,并引起幼鱼出现体轴上弯表型。本研究初步阐释了斑马鱼幼鱼早期神经底板处各种细胞类型的分布及定位特征,发现Notch信号对神经底板发育的重要调控作用。.
Keywords: Notch; cerebrospinal fluid-contacting neurons (CSF-cNs); floor plate; zebrafish.