Screening of Visual Center Specific Marker Molecules by Monoclonal Antibody Technique

为了阐明视网膜轴突与视觉中枢之间特异性神经元连接的分子背景，我们采用单克隆抗体制备技术筛选靶特异性标记分子。抗爪蟾蝌蚪（51-53期）机械分离的顶盖细胞的单克隆抗体A5（MAb-A5）与顶盖的第8和第9层（视神经支配的部位）以及间脑和中脑中的其他次要视觉中枢结合，但不与视网膜、视神经或视束结合。MAb-A5（A5抗原）的表位是分子量约140 K的细胞表面蛋白质分子。A5抗原首先出现在顶盖在第39阶段的发展时，顶盖入侵视网膜轴突开始。除视觉中枢外，A5抗原还出现在延髓和脊髓中非常有限的区域。当眼睛移植到爪蟾胚胎的背部时，来自移植眼的视网膜轴突优先到达髓质和脊髓中的A5抗原阳性区域。这些结果表明，A5抗原可能是视神经靶点的标记分子，并可能在优先引导或捕获向内生长的视网膜轴突中起重要作用。

To clarify the molecular background of the specific neuronal connection between retinal axons and visual centers, we undertook to screen target specific maker molecules by the monoclonal antibody producing technique. A monoclonal antibody A5 (MAb-A5) which was prepared against mechanically dissociated tectal cells of Xenopus tadpoles (at stages 51-53) bound to laminas 8 and 9 (the sites of optic nerve innervation) of the tectum and also other minor visual centers in the diencephalon and midbrain, but not to the retina, optic nerve or optic tract. The epitope of the MAb-A5 (A5 antigen) was a cell surface protein molecule approximately 140 K in molecular weight. The A5 antigen appeared in the tectum at first at stage 39 of development when tectal invasion by retinal axons was initiated. Besides the visual centers, the A5 antigen also appeared in very restricted regions in the medulla and spinal cord. When eyes were transplanted on the back of Xenopus embryos, retinal axons from the transplanted eye preferentially arrived at the A5 antigen-positive regions in the medulla and spinal cord. These findings suggest that the A5 antigen may be a marker molecule of optic nerve targets, and may play important roles in the preferential guiding or trapping of ingrowing retinal axons.