Tenne-Brown J, Puche A C, Key B
Department of Anatomy and Cell Biology, University of Melbourne, Parkville, Vic., Australia.
Int J Dev Biol. 1998 Sep;42(6):791-9.
Primary sensory olfactory axons arise from the olfactory neuroepithelium that lines the nasal cavity and then project via the olfactory nerve into the olfactory bulb. The beta-galactoside binding lectin, galectin-1, and its laminin ligand have been implicated in the growth of these axons along this pathway. In galectin-1 null mutant mice, a subpopulation of primary sensory olfactory axons fails to reach its targets in the olfactory bulb. In the present study we examined the spatiotemporal expression pattern of galectin-1 in normal mice in order to understand its role in the development of the olfactory nerve pathway. At E15.5, when olfactory axons have already contacted the olfactory bulb, galectin-1 was expressed in the cartilage and mesenchyme surrounding the nasal cavity but was absent from the olfactory neuroepithelium, nerve and bulb. Between E16.5 and birth galectin-1 began to be expressed by olfactory nerve ensheathing cells in the lamina propria of the neuroepithelium and nerve fibre layer. Galectin-1 was neither expressed by primary sensory neurons in the olfactory neuroepithelium nor by their axons in the olfactory nerve. Laminin, a galectin-1 ligand, also exhibited a similar expression pattern in the embryonic olfactory nerve pathway. Our results reveal that galectin-1 is dynamically expressed by glial elements within the nerve fibre layer during a discrete period in the developing olfactory nerve pathway. Previous studies have reported galectin-1 acts as a substrate adhesion molecule by cross-linking primary sensory olfactory neurons to laminin. Thus, the coordinate expression of galectin-1 and laminin in the embryonic nerve fibre layer suggests that these molecules support the adhesion and fasciculation of axons en route to their glomerular targets.
初级感觉嗅觉轴突起源于鼻腔内衬的嗅觉神经上皮，然后通过嗅神经投射到嗅球。β-半乳糖苷结合凝集素半乳糖凝集素-1及其层粘连蛋白配体与这些轴突沿该途径的生长有关。在半乳糖凝集素-1基因敲除突变小鼠中，一部分初级感觉嗅觉轴突无法到达嗅球中的目标。在本研究中，我们检测了正常小鼠中半乳糖凝集素-1的时空表达模式，以了解其在嗅神经通路发育中的作用。在胚胎第15.5天，当嗅觉轴突已经接触到嗅球时，半乳糖凝集素-1在鼻腔周围的软骨和间充质中表达，但在嗅觉神经上皮、神经和嗅球中不存在。在胚胎第16.5天至出生期间，半乳糖凝集素-1开始由神经上皮固有层和神经纤维层中的嗅觉神经鞘细胞表达。半乳糖凝集素-1既不在嗅觉神经上皮中的初级感觉神经元中表达，也不在嗅神经中的轴突中表达。层粘连蛋白作为半乳糖凝集素-1的配体，在胚胎嗅神经通路中也表现出类似的表达模式。我们的结果表明，在发育中的嗅神经通路的一个特定时期，半乳糖凝集素-1由神经纤维层内的神经胶质成分动态表达。先前的研究报道，半乳糖凝集素-1通过将初级感觉嗅觉神经元与层粘连蛋白交联而作为一种底物粘附分子。因此，半乳糖凝集素-1和层粘连蛋白在胚胎神经纤维层中的协同表达表明，这些分子支持轴突在通向其肾小球靶点的途中的粘附和成束。
