七鳃鳗鸟嘌呤转移因子Vav2分子克隆、表达及系统发育分析研究

鸟嘌呤转移因子Vav2为Vav家族成员，其在Ras-related GTP酶活性调节过程中发挥重要作用。本文首次从七鳃鳗体内克隆并表达出七鳃鳗Vav2分子（Lj-Vav2）。系统发育分析结果阐明，Lj-Vav2为脊椎动物Vav2基因家族的直系同源基因。进化动力学分析指明，CH结构域、DH结构域、PH结构域、C1结构域、SH3结构域、SH2结构域贯穿于脊椎动物Vav2家族的进化历程。实时定量PCR结果表明，Lj-Vav2分布于七鳃鳗心脏、肾脏、髓样组织、肝脏、鳃以及类淋巴细胞中，同时经过LPS刺激后淋巴细胞中Lj-Vav2的表达水平呈现明显上调趋势。综上，Lj-Vav2在七鳃鳗体内免疫防御过程中发挥重要作用。此外，我们的研究将为今后更好地阐明Lj-Vav2生物学功能奠定坚实的物质基础。

Molecular cloning, expression pattern and phylogenetic analysis of Guanine nucleotide exchange factor Vav2 in lamprey, Lampetra japonica

The Guanine nucleotide exchange factor Vav2 (Vav2) is a member of the Vav family that serves as an important regulators for the Rho family of Ras-related GTPases. In the current study, an ortholog (Lj-Vav2) of Vav2 was identified in the lamprey (Lampetra japonica). To elucidate the phylogenetic relationship of Vav2, the metazoan genome databases were analyzed to mine the ortholog of Vav. It was found that Vav2 genes were only existed in vertebrates and Lj-Vav2 was the original one found in agnathans. The evolutionary dynamics of conserved motifs of Vav2 were explored using combined amino acid sequence as markers, and it is revealed that the Calponin homology (CH) domain, Dbl-homologous (DH) domain, Pleckstrin homology (PH) domain, Cysteine-rich (C1) domains, Src homology 3 (SH3) domains and Src homology 2 (SH2) domain were conserved throughout the Vav2 gene family in vertebrates during gene evolution. Relative quantitative real-time PCR analysis showed that the Lj-Vav2 was distributed in the heart, kidney, supraneural myeloid body, liver, gill and lymphocyte-like cells. The Lj-Vav2 was found to be expressed in these tissues, and the level of which was upregulated in lymphocyte-like cells after the animal was stimulated with LPS. These results indicated that the Lj-Vav2 might be involved in the immune response of lymphocyte-like cells in lamprey. Meanwhile, our findings provided a foundation for further investigation of the function of Lj-Vav2 in the primary vertebrate.