Yaginuma H, Shiga T, Oppenheim R W
Department of Anatomy, University of Tsukuba, Japan.
Perspect Dev Neurobiol. 1993;1(4):205-15.
Axonal guidance mechanisms involved in pathway formation by avian spinal interneurons have been studied using a variety of different approaches. The earliest developing spinal interneurons can be divided into two groups on the basis of the initial direction of axonal outgrowth: circumferential cells (C-cells) and primitive longitudinal cells. Perturbation studies suggest that a chemotropic-like mechanism plays a role in the guidance of the C-cell axons toward the floor plate. The shape of floor plate cells is polarized mediolaterally (direction of axon growth) and only in this region do growth cones express integrin and contact the basement membrane. Pathway formation following dorsal to ventral spinal cord rotation indicates that the ventrolateral region of the neural tube may provide a permissive substrate for longitudinally advancing growth cones. In addition, following rostrocaudal rotation of three segments of the neural tube, the axons of dorsolateral border cells in the rotated segments modified their directionality according to the general rostrocaudal polarity of the embryo. Changes in cell adhesion molecule expression by the C-cell growth cones and axons is region and age specific. These observations suggest that a variety of mechanisms and cues are working in the guidance of spinal interneurons in each region of the pathway.
人们已经使用各种不同方法研究了参与禽类脊髓中间神经元通路形成的轴突导向机制。最早发育的脊髓中间神经元可根据轴突生长的初始方向分为两组：周向细胞（C细胞）和原始纵向细胞。干扰研究表明，一种趋化样机制在引导C细胞轴突向底板生长方面发挥作用。底板细胞的形状在内外侧（轴突生长方向）呈极化状态，只有在该区域生长锥才表达整合素并与基底膜接触。脊髓背腹旋转后的通路形成表明，神经管的腹外侧区域可能为纵向前进的生长锥提供了一个允许性底物。此外，在神经管三个节段进行头尾旋转后，旋转节段中背外侧边界细胞的轴突根据胚胎的总体头尾极性改变了其方向性。C细胞生长锥和轴突中细胞粘附分子表达的变化具有区域和年龄特异性。这些观察结果表明，多种机制和线索在通路各区域脊髓中间神经元的导向中发挥作用。
