Cloning And Expression Of Tbx2Subfamily Genes In Siberian Sturgeon,Acipenser Baerii

Tbx2subfamily including Tbx2, Tbx3, Tbx4and Tbx5genes, is a branch of a large transcription factor family, T-box family. Tbx2subfamily is birthed by tandem duplication from an ancestral gene Tbx2/3/4/5, long before the divergence of protostomes and deuterostomes (e.g., arthropods and vertebrates) at least600million years ago, and possibly before the divergence of poriferans and cnidarians (e.g., sponges and jellyfish). The expression of this gene family members (Tbx2-Tbx5) is widespread in virous tissues and organs. Tbx2subfamily well known to people by their significant function in development of body limb, is involved in morphogenesis and organogenesis in vertebrates, such as limb and eye development, heart remodeling and neural placode differentiation. In the present study, four cDNA fragments of Tbx2subfamily members and a full-length2,908bp Tbx3cDNA (AbTbx3) from Siberian sturgeon, Acipenser baerii were obtained by using RT-PCR and RACE technique. AbTbx3shares73.5%identity with its human homolog. Particularly, the DNA-binding domain of AbTbx3shared95.2%identity with human Tbx3, and its predicted secondary and three-dimensional structures were remarkably similar to human Tbx3. Phylogenetic analysis revealed that Tbx2, Tbx3, Tbx4and Tbx5of sturgeon were grouped with corresponding orthologs in other vertebrates, respectively. Meanwhile, the branch of Tbx2s and Tbx3s separated from the branch of Tbx4s and Tbx5s. Through quantitive Real Time-PCR, the expression of Tbx2and Tbx3was first detected at blastula stage during Siberian sturgeon embryonic development, increased gradually, reached its peak at early neurula stage and then decreased slightly as the increasingly expression of Tbx4and Tbx5. In adult sturgeon, Tbx2and Tbx3genes were widely expressed in various tissues and organs. Furthermore, the expression of Tbx3gene was significantly higher than Tbx2genes in the tissues which are constituted mainly by epithelium such as intestine, sensory epithelium and abdominal epithelium. Moreover, Tbx4and7bx5gene were expressed in pelvic fin and pectoral fin, respectively, and commonly expressed with Tbx2and Tbx3in eye, brain and heart. To better understand the role of Tbx3gene in the development of sturgeon, we carried out the whole mount in situ hybridization which showed that AbTbx3was mainly expressed in otic vesicle, hindbrain, branchial arch, dorsal notochord, pineal organ and dorsal fin bud in the larvae of stage37and43, suggesting that the expressional pattern of AbTbx3was conserved with other vertebrates, such as shark and mouse orthologs.