Ichijo H, Kawabata I
Department of Anatomy, Institute of Basic Medical Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8575, Japan.
J Neurosci. 2001 Dec 1;21(23):9304-14. doi: 10.1523/JNEUROSCI.21-23-09304.2001.
The axons of the retinal ganglion cells run on the diencephalotelencephalic boundary on their way to the tectum; however, they do not invade the telencephalon anteriorly. To investigate the mechanisms that prevent the retinal axons from entering the telencephalic territory, the effects of the telencephalic cells were examined on the outgrowth of the retinal axons in vitro; the retinal outgrowth was selectively inhibited by the cellular substrate derived from the telencephalon. The responsible factor for the selective inhibition was, furthermore, found in the telencephalic membranes and the fraction of peripheral membrane molecules from the telencephalon. Because the inhibitory effect was destroyed by chondroitinase ABC but not by heat, this inhibition was attributable to the carbohydrate chains of chondroitin sulfate proteoglycans (CSPGs) adhering to the membranes of the telencephalic cells. To understand the function of the telencephalic CSPGs on the retinal pathfinding in vivo, their carbohydrate chains [chondroitin sulfate glycosaminoglycan (CS-GAG)] were removed from the embryonic brains by intraventricular injection of chondroitinase ABC; the removal of CS-GAG resulted in an anterior enlargement of the optic tract. The results indicate that the telencephalic cells delimit the anterior border of the optic tract with their CSPGs and prevent the retinal axons from aberrantly entering the anterior territory.
视网膜神经节细胞的轴突在通往顶盖的途中，沿着间脑-端脑边界走行；然而，它们不会向前侵入端脑。为了研究阻止视网膜轴突进入端脑区域的机制，研究人员在体外检测了端脑细胞对视网膜轴突生长的影响；来自端脑的细胞底物选择性地抑制了视网膜轴突的生长。此外，在端脑膜和来自端脑的外周膜分子组分中发现了导致这种选择性抑制的因子。由于这种抑制作用可被软骨素酶ABC破坏，但不受热的影响，所以这种抑制作用归因于附着在端脑细胞表面的硫酸软骨素蛋白聚糖（CSPG）的糖链。为了了解端脑CSPG在体内视网膜路径寻找中的作用，通过脑室内注射软骨素酶ABC从胚胎大脑中去除其糖链[硫酸软骨素糖胺聚糖（CS-GAG）]；去除CS-GAG导致视束向前扩大。结果表明，端脑细胞通过其CSPG界定了视束的前缘，防止视网膜轴突异常进入前部区域。
