Feldner Julia, Becker Thomas, Goishi Katsutoshi, Schweitzer Jörn, Lee Percy, Schachner Melitta, Klagsbrun Michael, Becker Catherina G
Zentrum für Molekulare Neurobiologie Hamburg, Universität Hamburg, Hamburg, Germany.
Dev Dyn. 2005 Nov;234(3):535-49. doi: 10.1002/dvdy.20520.
Neuropilin-1, a receptor for axon-repellent semaphorins and vascular endothelial growth factor (VEGF), functions both in angiogenesis and axon growth. Here, we show strong expression of neuropilin-1a in primary motor neurons in the trunk of embryonic zebrafish. Reducing the expression of neuropilin-1a using antisense morpholino oligonucleotides induced aberrant branching of motor nerves, additional exit points of motor nerves from the spinal cord, and migration of neurons out of the spinal cord along the motor axon pathway in a dose-dependent manner. These phenotypes could be partially rescued by co-injecting neuropilin-1a mRNA. Other axons in the spinal cord and head appeared unaffected by the morpholino treatment. In addition, neuropilin-1a morpholino treatment disturbed normal formation of blood vessels in the trunk of 24 hours postfertilization embryos, as shown by microangiography. Morpholinos to VEGF also disturbed formation of blood vessels but did not affect motor axons, indicating that correct formation of blood vessels is not needed for the growth of primary motor axons. Morpholinos to the semaphorin 3A homologs semaphorin 3A1 and semaphorin 3A2 also had no effect on motor axon growth. However, combined injections of neuropilin-1a morpholino, at a concentration that did not elicit axonal aberrations when injected alone, with VEGF, semaphorin 3A1, or semaphorin 3A2 morpholinos synergistically increased the proportion of embryos showing aberrant motor axon growth. Thus, neuropilin-1a in primary motor neurons may integrate signals from several ligands and is needed for proper segmental growth of primary motor nerves in zebrafish.
神经纤毛蛋白-1是轴突排斥性信号素和血管内皮生长因子（VEGF）的受体，在血管生成和轴突生长中均发挥作用。在此，我们展示了神经纤毛蛋白-1a在胚胎斑马鱼躯干初级运动神经元中的强烈表达。使用反义吗啉代寡核苷酸降低神经纤毛蛋白-1a的表达，会以剂量依赖的方式诱导运动神经的异常分支、运动神经从脊髓的额外出口点以及神经元沿运动轴突路径从脊髓迁出。通过共注射神经纤毛蛋白-1a mRNA可部分挽救这些表型。脊髓和头部的其他轴突似乎不受吗啉代处理的影响。此外，如微血管造影所示，神经纤毛蛋白-1a吗啉代处理扰乱了受精后24小时胚胎躯干中血管的正常形成。针对VEGF的吗啉代也扰乱了血管形成，但不影响运动轴突，表明初级运动轴突的生长不需要血管的正确形成。针对信号素3A同源物信号素3A1和信号素3A2的吗啉代对运动轴突生长也没有影响。然而，将单独注射时不会引发轴突畸变浓度的神经纤毛蛋白-1a吗啉代与VEGF、信号素3A1或信号素3A2吗啉代联合注射，会协同增加显示运动轴突生长异常的胚胎比例。因此，初级运动神经元中的神经纤毛蛋白-1a可能整合来自几种配体的信号，是斑马鱼初级运动神经正常节段生长所必需的。
