Bernhardt R R, Schachner M
Zentrum für Molekulare Neurobiologie, Universität Hamburg, Hamburg, D-20246, Germany.
Dev Biol. 2000 May 1;221(1):206-19. doi: 10.1006/dbio.2000.9673.
Chondroitin sulfates have been implicated in the promotion and in the inhibition of axon growth. In the zebrafish embryo, chondroitin sulfates are present at the interface of the somites and the notochord where spinal motor axons extend ventrally to establish the midsegmental ventral motor nerves. Injection of chondroitinase ABC prior to motor axon outgrowth effectively removed all chondroitin sulfate immunoreactivity and induced abnormal axonal outgrowth in many (39%) of the ventral motor nerves. The most common abnormality was the formation of side branches, approximately half of which extended posteriorly, the others anteriorly. The effect was specific to the removal of chondroitin sulfates, since injections of vehicle solution or of heparinase III did not affect the ventral motor nerves. Electron microscopic examination demonstrated that the injections caused no damage to spinal cord, somite, and notochord. This suggests that chondroitin sulfates normally constrain the outgrowth of the ventral motor nerves. Consistent with this hypothesis, injections of soluble chondroitin sulfates, either as a mixture or individually, led to truncated or missing ventral motor nerves. Truncations were most frequent after injection of chondroitin sulfate-B (up to 23%) while chondroitin sulfate-A had a lesser, and chondroitin sulfate-C no apparent, effect.
硫酸软骨素与轴突生长的促进和抑制均有关联。在斑马鱼胚胎中，硫酸软骨素存在于体节和脊索的界面处，脊髓运动轴突在此处向腹侧延伸以建立节段中部的腹侧运动神经。在运动轴突长出之前注射硫酸软骨素酶ABC可有效去除所有硫酸软骨素免疫反应性，并在许多（39%）腹侧运动神经中诱导异常的轴突生长。最常见的异常是侧支的形成，其中约一半向后延伸，另一半向前延伸。这种效应是硫酸软骨素去除所特有的，因为注射溶剂或肝素酶III对腹侧运动神经没有影响。电子显微镜检查表明，注射不会对脊髓、体节和脊索造成损伤。这表明硫酸软骨素通常会限制腹侧运动神经的生长。与这一假设一致的是，注射可溶性硫酸软骨素，无论是混合注射还是单独注射，都会导致腹侧运动神经截断或缺失。注射硫酸软骨素-B后截断最为频繁（高达23%），而硫酸软骨素-A的影响较小，硫酸软骨素-C则没有明显影响。
