Hirata T, Fujisawa H, Wu J Y, Rao Y
Division of Brain Function, National Institute of Genetics, Mishima 411-8540, Japan.
J Neurosci. 2001 Apr 1;21(7):2373-9. doi: 10.1523/JNEUROSCI.21-07-02373.2001.
During development, mitral cells, the major output neurons of the olfactory bulb, project their axons caudolaterally into the telencephalon and form the lateral olfactory tract (LOT). Two types of guidance cues have been suggested for this projection. First, a long-range factor Slit, which is secreted from the septum, repels mitral cell axons into a caudolateral direction. Second, the pathway of mitral cell axons contains a subset of neurons designated as lot cells, which guide the axons through short-range interactions. It is not clear how these two guidance cues relate to each other and how they share the physiological roles. Here we examined the behavior of mitral cell axons in organotypic culture on ectopic application of Slit and inhibition of endogenous Slit signaling. The results suggested that the short-range guidance cue in the LOT pathway functions independently from Slit. Furthermore, our results showed that removal of the septum and inhibition of Slit signaling did not affect the projection of mitral cell axons. Although the septum and exogenous Slit can repel olfactory bulb axons, our results cast doubts on the physiological relevance of the septum and endogenous Slit in guiding the projection of mitral cell axons.
在发育过程中，嗅球的主要输出神经元——二尖瓣细胞，将其轴突向尾外侧投射到端脑并形成外侧嗅束（LOT）。对于这种投射，已提出两种类型的导向线索。第一，一种由隔膜分泌的远距离因子Slit，将二尖瓣细胞轴突排斥向尾外侧方向。第二，二尖瓣细胞轴突的路径包含一组被称为LOT细胞的神经元，它们通过短程相互作用引导轴突。目前尚不清楚这两种导向线索如何相互关联，以及它们如何分担生理作用。在这里，我们通过异位应用Slit和抑制内源性Slit信号传导，研究了器官型培养中二尖瓣细胞轴突的行为。结果表明，LOT途径中的短程导向线索独立于Slit发挥作用。此外，我们的结果表明，去除隔膜和抑制Slit信号传导并不影响二尖瓣细胞轴突的投射。尽管隔膜和外源性Slit可以排斥嗅球轴突，但我们的结果对隔膜和内源性Slit在引导二尖瓣细胞轴突投射方面的生理相关性提出了质疑。
