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MOLECULAR INSIGHTS INTO B CELL ACTIVATING FACTOR FROM BLACK ROCKFISH Sebastes schlegelii WITH ITS IMMUNE RESPONSES

G. I. Godahewa1,2*, N. C. N. Perera and Jehee Lee
E-mail: imarshana@gmail.com
 
1Department of Marine Life Sciences, School of Marine Biomedical Sciences, Jeju National University, Jeju Self-Governing Province 690-756, Republic of Korea
2Fish Vaccine Research Center, Jeju National University, Jeju Self-Governing Province 690-756, Republic of Korea

Tumor necrosis factor (TNF) family members are vital immune regulators of the biological system. B cell activating factor (BAFF) is considered as an important member of the TNF family cytokines that plays a major role in B cell survival, proliferation and differentiation. The biological function of BAFF is facilitated by three specific receptors which are B cell maturation antigen (BCMA), transmembrane activator and calcium-modulating/cyc-lophilin ligand-interacting protein (TACI) and BAFF-receptor (BAFF-R or BR3). Previous studies suggested that BAFF-R is the basic BAFF binding receptor responsible for B cell development and survival. However, growing amounts of evidences suggest that excessive level of BAFF and its receptors production may disturb immune tolerance by allowing the survival of auto-reactive B-cells, resulting in autoimmune disease. In order to explore the teleost immunity, we are studying the rockfish (Sebastes schlegelii) BAFF (SsBAFF) gene as per molecular characterization and transcriptional regulation upon immune stimulations. Characteristic features of cDNA and amino acid sequence of SsBAFF were discovered by different bioinformatics tools. The SsBAFF mRNA expressions in healthy and challenged tissues were assessed by quantitative real time PCR (qPCR). The conceptually translated protein of SsBAFF gene resembled the conventional domain structure of its known counterparts and demonstrated significant homology. In fact, SsBAFF possessed 804 bp of a putative coding sequence (CDS) that coded into 267 aa polypeptide with a 29 kDa molecular weight. The characteristic TNF superfamily domain was identified. Also potential N-linked glycosylation sites were observed. Pairwise homology analysis exhibited highest identity (87%) with the Epinephelus awoara BAFF. In addition, phylogenetic evolutionary analysis of SsBAFF was shown closer relatedness with E. awoara counterpart. The SsBAFF mRNA was strongly transcribed in rockfish spleen where other examined tissues express the ubiquitous expressional pattern. Moreover, it was noted that SsBAFF mRNA level is significantly up-regulated at 3 h post infection of lipopolysaccharide, Streptococcus iniae and poly I:C in the spleen tissue. Findings of the current study collectively provide an overall understanding of the immune related BAFF gene of teleost origin.  

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