Cheng H J, Nakamoto M, Bergemann A D, Flanagan J G
Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115, USA.
Cell. 1995 Aug 11;82(3):371-81. doi: 10.1016/0092-8674(95)90426-3.
Topographic maps with a defined spatial ordering of neuronal connections are a key feature of brain organization. Such maps are believed to develop in response to complementary position-specific labels in presynaptic and postsynaptic fields. However, the complementary labeling molecules are not known. In the well-studied visual map of retinal axons projecting to the tectum, the labels are hypothesized to be in gradients, without needing large numbers of cell-specific molecules. We recently cloned ELF-1 as a ligand for Eph family receptors. Here, RNA hybridization shows matching expression gradients for ELF-1 in the tectum and its receptor Mek4 in the retina. Binding activity detected with alkaline phosphatase fusions of ELF-1 and Mek4 also reveals gradients and provides direct evidence for molecular complementarity of gradients in reciprocal fields. ELF-1 and Mek4 may therefore play roles in retinotectal development and have properties predicted of topographic mapping labels.
具有明确神经元连接空间排序的地形图是大脑组织的一个关键特征。人们认为，这类图谱是在突触前和突触后区域互补的位置特异性标记的作用下形成的。然而，互补标记分子尚不清楚。在研究充分的视网膜轴突投射到顶盖的视觉图谱中，这些标记被推测为梯度分布，无需大量细胞特异性分子。我们最近克隆了ELF-1作为Eph家族受体的配体。在这里，RNA杂交显示ELF-1在顶盖及其受体Mek4在视网膜中的表达梯度相匹配。用ELF-1和Mek4的碱性磷酸酶融合物检测到的结合活性也显示出梯度，并为相互区域中梯度的分子互补性提供了直接证据。因此，ELF-1和Mek4可能在视网膜顶盖发育中发挥作用，并具有地形图标记所预测的特性。
