Latimer Andrew J, Appel Bruce
Department of Biological Sciences, Vanderbilt University, U7211 BSB/MRBIII, 465 21st Avenue South, Nashville, TN 37232, USA.
Dev Biol. 2006 Oct 15;298(2):392-402. doi: 10.1016/j.ydbio.2006.05.039. Epub 2006 Jun 30.
Notochord and floor plate cells are sources of molecules that pattern tissues near the midline, including the spinal cord. Hypochord cells are also found at the midline of anamniote embryos and are important for aorta development. Delta-Notch signaling regulates midline patterning in the dorsal organizer by inhibiting notochord formation and promoting hypochord and possibly floor plate development, but the precise mechanisms by which this regulation occurs are unknown. We demonstrate here that floor plate and hypochord cells arise from distinct regions of the zebrafish shield. Blocking Notch signaling during gastrulation entirely prevented hypochord specification but only reduced the number of floor plate cells that developed compared to control embryos. In contrast, elevation of Notch signaling at the beginning of gastrulation caused expansion of hypochord at the expense of notochord, but floor plate was not affected. A cell proliferation assay revealed that Notch signaling maintains dividing floor plate progenitors. Together, our results indicate that Notch signaling regulates allocation of appropriate numbers of different midline cells by different mechanisms.
脊索和底板细胞是为包括脊髓在内的中线附近组织定型的分子来源。下索细胞也存在于无羊膜动物胚胎的中线处，对主动脉发育很重要。Delta-Notch信号通过抑制脊索形成并促进下索以及可能的底板发育来调节背侧组织者中的中线模式，但这种调节发生的确切机制尚不清楚。我们在此证明，底板和下索细胞源自斑马鱼胚盾的不同区域。原肠胚形成期间阻断Notch信号完全阻止了下索的特化，但与对照胚胎相比，仅减少了发育的底板细胞数量。相反，原肠胚形成开始时Notch信号的增强导致下索以脊索为代价而扩张，但底板不受影响。细胞增殖试验表明，Notch信号维持正在分裂的底板祖细胞。总之，我们的结果表明，Notch信号通过不同机制调节不同中线细胞的适当数量分配。
