Schäfer Matthias, Kinzel Doris, Winkler Christoph
Department of Physiological Chemistry I, Biocenter, University of Würzburg, Am Hubland, 97074 Würzburg, Germany.
Dev Biol. 2007 Jan 1;301(1):117-29. doi: 10.1016/j.ydbio.2006.09.018. Epub 2006 Sep 16.
The floor plate is a signaling center in the ventral neural tube of vertebrates with important functions during neural patterning and axon guidance. It is composed of a centrally located medial floor plate (MFP) and a bilaterally positioned lateral floor plate (LFP). While the role of the MFP as source of signaling molecules like, e.g., Sonic Hedgehog (Shh) is well understood, the exact organization and function of the LFP are currently unclear. Based on expression analyses, the one cell wide LFP in zebrafish has been postulated to be a homogenous structure. We instead show that the zebrafish trunk LFP is discontinuously arranged. Single LFP cells alternate with p3 neuronal precursor cells, which develop V3 interneurons along the anteroposterior (AP) axis. Our mutant analyses indicate that both, formation of LFP and p3 cells require Delta-Notch signaling. Importantly, however, the two cell types are differentially regulated by Hedgehog (HH) and Nkx2.2 activities. This implicates a novel mechanism of neural tube patterning, in which distinct cell populations within one domain of the ventral neural tube are differently specified along the AP axis. We conclude that different levels of HH and Nkx2.2 activities are responsible for the alternating appearance of LFP and p3 neuronal progenitor cells in the zebrafish ventral neural tube.
底板是脊椎动物腹侧神经管中的一个信号中心，在神经模式形成和轴突导向过程中具有重要功能。它由位于中央的内侧底板（MFP）和双侧定位的外侧底板（LFP）组成。虽然MFP作为信号分子（如音猬因子（Shh））来源的作用已得到充分理解，但LFP的确切组织和功能目前尚不清楚。基于表达分析，斑马鱼中单个细胞宽度的LFP被假定为一种同质结构。相反，我们发现斑马鱼躯干LFP是不连续排列的。单个LFP细胞与p3神经元前体细胞交替出现，p3神经元前体细胞沿前后（AP）轴发育成V3中间神经元。我们的突变分析表明，LFP和p3细胞的形成都需要Delta-Notch信号传导。然而，重要的是，这两种细胞类型受刺猬因子（HH）和Nkx2.2活性的差异调节。这暗示了一种神经管模式形成的新机制，其中腹侧神经管一个区域内的不同细胞群体沿AP轴被不同地指定。我们得出结论，不同水平的HH和Nkx2.2活性导致了斑马鱼腹侧神经管中LFP和p3神经元祖细胞交替出现。
