The function of Semaphorin on the neural network formation in the olfactory system.

Semaphorin 3A（Sema 3A）排斥表达神经纤毛蛋白-1（Sema 3A的受体）的生长的嗅觉轴突。Sema 3A介导的轴突引导似乎是必要的，在嗅球的肾小球感觉地图的形成。为了了解Sema 3A是否以及如何参与感觉地图的形成，我们研究了成年Sema 3A缺陷小鼠嗅球中的肾小球地图。在野生型小鼠中，Neuropilin-1阳性肾小球形成外侧和内侧带，并避开嗅球的前内侧和腹侧区域。在Sema 3A缺陷的嗅球神经纤毛蛋白-1阳性肾小球遍布整个嗅球，我们始终发现神经纤毛蛋白-1阳性肾小球的异位排列在前内侧和腹侧区域。此外，一个特定的子集Neuropilin-1阴性和OCAM阳性肾小球，特别是那些在前内侧区，从突变嗅球消失。这些结果显示了Sema 3A在嗅球中肾小球的空间排列中的关键作用。光学成像从背嗅球显示，扭曲的肾小球地图保守的分子特征域。然而，结构域的位置发生了变化，这表明在Sema 3A缺陷的嗅球中肾小球地图的二级重排。

Semaphorin 3A (Sema3A) repels growing olfactory axons that express Neuropilin-1, a receptor for Sema3A. The Sema3A-mediated axon guidance seems to be essential for the formation of the glomerular sensory map in the olfactory bulb. To understand whether and how Sema3A is involved in the sensory map formation, we examined the glomerular map in the olfactory bulb of adult Sema3A-deficient mice. In the wild-type mice Neuropilin-1-positive glomeruli form the lateral and medial bands and avoid the anteromedial and ventral regions of the olfactory bulb. In the Sema3A-deficient olfactory bulb Neuropilin-1-positive glomeruli spread over the entire olfactory bulb and we consistently found the ectopic arrangement of Neuropilin-1-positive glomeruli in the anteromedial and ventral regions. In addition, a specific subset of Neuropilin-1-negative and OCAM-positive glomeruli, especially those in the anteromedial region, disappeared from the mutant olfactory bulb. These results show a critical role for Sema3A in the spatial arrangement of glomeruli in the olfactory bulb. Optical imaging from the dorsal olfactory bulb showed that the distorted glomerular map conserved molecular-feature domains. However, the positions of the domains were shifted, which suggests a secondary rearrangement of the glomerular map in the Sema3A-deficient olfactory bulb.