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.