DIFFERENTIAL MECHANISM IN NERVE REGENERATION BETWEEN CNS AND PNS DIFFERENCE

为了鉴定神经再生相关分子，我们使用了一种称为差异显示的方法。我们分别从神经损伤的舌下神经核和正常舌下神经核中纯化RNA，并将这些RNA进一步处理用于差异显示。本方法成功地证明了几个候选基因，在神经损伤后上调。使用原位杂交组织化学的筛选进一步挤压候选者。这些分子是（1）属于谷氨酸代谢的分子，（2）与自由基清除剂有关的分子，（3）某组生长因子受体，（4）沿着某种细胞内信号传导的分子，以及（5）与氧化还原调节有关的分子。由于这些分子来源于成年受损的运动神经元，即使在神经损伤后也能存活。我们研究了这些分子是否也对新生运动神经元中的类似类型的神经损伤做出反应，这些运动神经元注定会因神经损伤而死亡。切断成年和幼年舌下神经轴突，进行原位杂交，以确定转录调控。在这个比较中，我们发现一些分子有能力对成年人的神经损伤做出反应，但在幼崽中没有。例如，LIF-R和GDNFR（α）在成年人中对神经损伤有积极反应，但在幼崽中呈负反应。这种对神经损伤的相反反应可能是神经损伤后成年运动神经元存活而幼鼠运动神经元死亡的原因之一。

In order to identify nerve regeneration associated molecules, we have used a method called the differential display. We purified RNA from nerve injured-and normal hypoglossal nuclei respectively, and these RNAs were further processed for the differential display. The present method successfully demonstrated several candidate genes which were up-regulated after nerve injury. A screening using in situ hybridization histochemistry further squeeze the candidates. These are (1) molecules belonging to glutamate metabolism, (2) molecules implicated in free radical scavenger, (3) a certain group of growth factor receptors, (4) molecules along a certain intracellular signaling, and (5) molecules implicated in redox regulation. Since these molecules were derived from adult injured motoneurons which can survive even after nerve injury. We examined if these molecules were also respond to a similar type of nerve injury in new born motoneurons which were fated to die by nerve injury. Both adult and pups hypoglossal nerve were axotomized, and in situ hybridization was carried out to identify transcription regulations. In this comparison, we found that some molecules have an ability to respond to nerve injury in adult, but not in pups. For instance, LIF-R and GDNFR (alpha) respond to nerve injury positively in adult, but negatively in pups. This opposite responses to nerve injury may be a reason why adult motoneurons can survive and pup's motoneurons die after nerve injury.