Center for Neuroscience, Shantou University Medical College, 22 Xin Ling Road, Shantou, Guangdong Province 515041, PR China.
Center for Neuroscience, Shantou University Medical College, 22 Xin Ling Road, Shantou, Guangdong Province 515041, PR China.
Exp Neurol. 2014 Nov;261:196-205. doi: 10.1016/j.expneurol.2014.06.006. Epub 2014 Jun 11.
Based on the observation that the tumor suppressor gene PTEN (phosphatase and tensin homolog) reduces regeneration after spinal cord injury (SCI) as evidenced in the PTEN knockout mouse, we have investigated the function of Ptena and Ptenb, the two zebrafish homologs of mammalian PTEN, in adult zebrafish after spinal cord injury with the aim to assess the contribution of the two zebrafish genes to functional recovery in an animal species that spontaneously recovers from central nervous system injury. The inhibition of Ptena expression by antisense morpholino (MO) application improved spinal cord regeneration through 4 to 5weeks after injury. Retrograde tracing showed regrowth of axons from neurons of the regeneration-competent nucleus of the medial longitudinal fascicle in the brainstem in the Ptena MO-treated fish. Ptenb MO-treated fish recovered as well as control MO-treated fish at 4 and 5weeks after SCI, with their locomotion being similar to that of sham-injured and non-injured fish. The mRNA levels of Ptena were upregulated after SCI at the early stage after injury (12h and 6days) caudal to the lesion site, compared to the non-injured control, while the levels of Ptenb were upregulated only at 12h after injury. In situ hybridization experiments were in agreement with the qPCR measurements. At the protein level, Ptena was found to be expressed in spinal motoneurons and immature neurons. These results indicate that Ptena, but not Ptenb, inhibits regeneration in zebrafish, thus sharing this feature with PTEN in mammals. The fact that zebrafish regenerate better than mammals despite the inhibitory presence of Ptena is likely due to regeneration-conducive molecules that tip the balance from inhibition to enhancement. Interestingly, although Ptena and Ptenb have been shown to be functionally redundant in promoting the development of the fish larval central nervous system, they are not functionally redundant in the adult, suggesting that regeneration in fish is not predominantly due to the overall recapitulation of development.
基于肿瘤抑制基因 PTEN（磷酸酶和张力蛋白同源物）减少脊髓损伤（SCI）后再生的观察结果，我们研究了两种斑马鱼同源物 Ptena 和 Ptenb 在成年斑马鱼 SCI 后的功能，目的是评估这两个斑马鱼基因对中枢神经系统损伤自发恢复的动物物种功能恢复的贡献。通过应用反义 morpholino（MO）抑制 Ptena 的表达，促进了损伤后 4 至 5 周的脊髓再生。逆行追踪显示，在 Ptena MO 处理的鱼中，来自脑桥中再生能力核的中纵束的神经元的轴突再生。Ptenb MO 处理的鱼与对照 MO 处理的鱼在 SCI 后 4 周和 5 周时恢复情况相同，其运动与假损伤和未损伤的鱼相似。与未损伤的对照相比，在损伤后早期（损伤部位下游的 12h 和 6d），Ptena 的 mRNA 水平上调，而 Ptenb 的水平仅在损伤后 12h 上调。原位杂交实验与 qPCR 测量结果一致。在蛋白质水平上，发现 Ptena 在脊髓运动神经元和未成熟神经元中表达。这些结果表明，Ptena 抑制了斑马鱼的再生，与哺乳动物中的 PTEN 具有相同的特征，而 Ptenb 则没有。尽管斑马鱼存在抑制性的 Ptena，但它们的再生能力比哺乳动物好，这可能是由于存在促进再生的分子，使平衡从抑制变为增强。有趣的是，尽管 Ptena 和 Ptenb 在促进鱼类幼虫中枢神经系统发育方面表现出功能冗余，但在成年鱼中它们并非功能冗余，这表明鱼类的再生主要不是由于整体重演发育。
