DIFFERENTIAL MECHANISM IN NERVE REGENERATION BETWEEN CNS AND PNS DIFFERENCE

为了识别神经再生相关分子，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和正常舌下神经核中提纯了RNA，并对这些RNA进行了进一步的处理，用于差异显示。目前的方法成功地证明了神经损伤后上调的几个候选基因。用原位杂交组织化学进行的筛选进一步挤压了候选者。这些分子是(1)谷氨酸代谢的分子，(2)与自由基清除剂有关的分子，(3)一组生长因子受体，(4)沿某种细胞内信号转导的分子，(5)与氧化还原调节有关的分子。因为这些分子来自成年损伤的运动神经元，即使在神经损伤后也能存活。我们检查了这些分子是否也对新生的运动神经元中类似类型的神经损伤做出反应，这些神经元注定会因神经损伤而死亡。成年和幼鼠均切断舌下神经，并进行原位杂交以确定转录调控。在这一比较中，我们发现一些分子对成年动物的神经损伤有反应的能力，但在幼鼠身上没有。例如，在成年动物中，LIF-R和GDNFR(α)对神经损伤的反应是积极的，而在幼鼠中则是消极的。这种对神经损伤的相反反应可能是成年运动神经元能够存活，而幼崽的运动神经元在神经损伤后死亡的原因之一。

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.