Bak Magdalena, Fraser Scott E
Division of Biology, Biological Imaging Center, Beckman Institute, California Institute of Technology, Pasadena, CA 91125, USA.
Development. 2003 Oct;130(20):4999-5008. doi: 10.1242/dev.00713.
Early neuronal scaffold development studies suggest that initial neurons and their axons serve as guides for later neurons and their processes. Although this arrangement might aid axon navigation, the specific consequence(s) of such interactions are unknown in vivo. We follow forebrain commissure formation in living zebrafish embryos using timelapse fluorescence microscopy to examine quantitatively commissural axon kinetics at the midline: a place where axon interactions might be important. Although it is commonly accepted that commissural axons slow down at the midline, our data show this is only true for leader axons. Follower axons do not show this behavior. However, when the leading axon is ablated, follower axons change their midline kinetics and behave as leaders. Similarly, contralateral leader axons change their midline kinetics when they grow along the opposite leading axon across the midline. These data suggest a simple model where the level of growth cone exposure to midline cues and presence of other axons as a substrate shape the midline kinetics of commissural axons.
早期的神经元支架发育研究表明，最初的神经元及其轴突为后来的神经元及其突起提供引导。尽管这种排列可能有助于轴突导航，但这种相互作用的具体后果在体内尚不清楚。我们利用延时荧光显微镜观察活斑马鱼胚胎前脑连合的形成，以定量研究中线处连合轴突的动力学：轴突相互作用可能很重要的一个部位。虽然人们普遍认为连合轴突在中线处会减速，但我们的数据表明，只有引导轴突才是如此。跟随轴突则没有这种行为。然而，当引导轴突被切除时，跟随轴突会改变其在中线处的动力学，并表现得像引导轴突。同样，当对侧引导轴突沿着相反的引导轴穿过中线生长时，它们也会改变其在中线处的动力学。这些数据提出了一个简单的模型，即生长锥暴露于中线信号的程度以及其他轴突作为底物的存在塑造了连合轴突在中线处的动力学。
