人类新基因netrin-G 2的初步分析

Netrins是与层粘连蛋白相关的、高度保守的小分子分泌蛋白家族成员，在细胞迁移和轴突导向活动中具有重要的作用，其同源物在多种模式动物中均已发现.Netrins分为2个亚家族:netrins和netrin-Gs；其中的netrin-G亚家族各成员之间具有高度的相似性.目前,在人类中得到确证的只有netrin-G₁，推测在人类中应该还有其它的netrin-G亚家族成员以及编码它的基因.从20周龄人胚中提取脑组织的总RNA，用PCR cDNA文库试剂盒制备脑组织cDNA文库，再用特异性引物进行PCR扩增，得到1条人netrin-G的全长cDNA，命名为人netrin-G₂，用Northern杂交研究其表达，用进化树分析其与netrin家族各成员间的关系；证实人netrin-G₂确实为netrin-G亚家族的1个新成员，该基因位于染色体的9q34，大小为2 428 bp，含有1个1 593 bp的假定开放阅读框，起始密码子为86位的甲硫氨酸，终止密码子为1 678位的TGA，可编码1个大小为530个氨基酸的蛋白质；Northern杂交显示，人netrin-G₂在脑组织中特异性表达，而在其它组织中却很少发现，推测人netrin-G₂可能在中枢神经系统的发育过程中具有重要的作用，可能与刺激性神经冲动的传递以及神经调节有关.

Primary Analysis of Human Novel Gene netrin-G2

The netrins is one of a small phylogenetically conserved family members which are laminin related secreted proteins. The netrins play a critical role in cell migration and axon guidance. Its homologues have been widely described in various animals. Netrins can be subdivided into two subfamilies, classical netrins and netrin-Gs. Since the members of netrin-G subfamily exhibit a high degree of similarity and there is only one member, netrin-G₁, identified in human, it is presumed that there must be new members in human too. The total RNA in brains was extracted from 20 weeks human embryos, and the cDNA library was constructed by using a cDNA PCR Library Kit. A full length human netrin-G cDNA, which named netrin-G₂, was generated by using special primers and PCRs. Finally, a primary study about the expression of human netrin-G₂ was carried out by Northern blot analysis and a research about the relationship between human netrin-G₂ and other netrins family members was determined by phylogenetic tree analysis. Human netrin-G₂ was indeed a new member of netrin-G subfamily, which mapped to chromosome 9q34. The final assembled cDNA sequence of human netrin-G₂ was 2 428 bp in length and had a putative open reading frame of 1 593 bp, which could encoding a 530 amino acid residures, and a start codon for methionine at the position 86 and TGA stop codon at position 1 678 were found. Northern blot analysis revealed that netrin-G₂ were expressed specifically in brain and seldom in other tissues. These results suggested that netrin-G₂ might play an important role in the development of central nervous system and might contribute to excitatory neurotransmission and neural modulation.