Higgins M R, Gibson N J, Eckholdt P A, Nighorn A, Copenhaver P F, Nardi J, Tolbert L P
Arizona Research Laboratories Division of Neurobiology, University of Arizona, Tucson, Arizona 85721, USA.
Dev Biol. 2002 Apr 1;244(1):134-54. doi: 10.1006/dbio.2002.0583.
During development of the primary olfactory projection, olfactory receptor axons must sort by odor specificity and seek particular sites in the brain in which to create odor-specific glomeruli. In the moth Manduca sexta, we showed previously that fasciclin II, a cell adhesion molecule in the immunoglobulin superfamily, is expressed by the axons of a subset of olfactory receptor neurons during development and that, in a specialized glia-rich "sorting zone," these axons segregate from nonfasciclin II-expressing axons before entering the neuropil of the glomerular layer. The segregation into fasciclin II-positive fascicles is dependent on the presence of the glial cells in the sorting zone. Here, we explore the expression patterns for different isoforms of Manduca fasciclin II in the developing olfactory system. We find that olfactory receptor axons express transmembrane fasciclin II during the period of axonal ingrowth and glomerulus development. Fascicles of TM-fasciclin II+ axons target certain glomeruli and avoid others, such as the sexually dimorphic glomeruli. These results suggest that TM-fasciclin II may play a role in the sorting and guidance of the axons. GPI-linked forms of fasciclin II are expressed weakly by glial cells associated with the receptor axons before they reach the sorting zone, but not by sorting-zone glia. GPI-fasciclin II may, therefore, be involved in axon-glia interactions related to stabilization of axons in the nerve, but probably not related to sorting.
在初级嗅觉投射的发育过程中，嗅觉受体轴突必须根据气味特异性进行分类，并在大脑中寻找特定的位点来形成气味特异性的嗅小球。在烟草天蛾中，我们之前已经表明，免疫球蛋白超家族中的细胞粘附分子成束蛋白II在发育过程中由一部分嗅觉受体神经元的轴突表达，并且在一个富含胶质细胞的特殊“分类区”中，这些轴突在进入嗅小球层的神经纤维网之前与不表达成束蛋白II的轴突分离。向成束蛋白II阳性束的分离依赖于分类区中胶质细胞的存在。在这里，我们探索了烟草天蛾成束蛋白II不同异构体在发育中的嗅觉系统中的表达模式。我们发现嗅觉受体轴突在轴突向内生长和嗅小球发育期间表达跨膜成束蛋白II。跨膜成束蛋白II阳性轴突的束靶向某些嗅小球并避开其他嗅小球，比如性二态性嗅小球。这些结果表明跨膜成束蛋白II可能在轴突的分类和导向中起作用。与受体轴突相关的胶质细胞在轴突到达分类区之前微弱表达糖基磷脂酰肌醇连接形式的成束蛋白II，但分类区胶质细胞不表达。因此，糖基磷脂酰肌醇连接的成束蛋白II可能参与与神经中轴突稳定相关的轴突 - 胶质细胞相互作用，但可能与分类无关。
