Abstract
A full-length cDNA encoding the immunoglobulin (IgM) heavy chain gene of Nile tilapia was successfully cloned using the 5’ and 3’ RACE techniques. The complete cDNA of the Nile tilapia IgM heavy chain gene is 1,921 bp in length and has an open reading frame (ORF) of 1,740 bp, which corresponds to 580 amino acid residues. The deduced amino acid sequence of the Nile tilapia IgM heavy chain includes a typical secretory IgM heavy chain designated On and a variable region that is connected to 4 constant regions to form the L H -V H -C µ 1-C µ 2-C µ 3-C µ 4 pattern. Comparisons of the nucleotide and amino acid sequences of On -sIgM with IgM heavy chains of other organisms showed the highest similarity scores of 62.6 and 55.4%, respectively, to the orange-spotted grouper ( Epinephelus coioides ). Structural analysis of 126 cDNAs encoding variable domains of the IgM heavy chain revealed that at least 9 V H families, 6 D H segments and 4 J H families were utilized using several mechanisms to generate the repertoire of antigen-binding domains. Variation analysis of the variable domains indicated that the amino acid sequences of the framework regions (FRs) were less variable than those of the complementarity determining regions (CDRs), among which the most variable was CDR3. Tissue expression profile analysis using quantitative real-time RT-PCR of healthy Nile tilapia showed that the IgM heavy chain gene was ubiquitously expressed in all 13 tested tissues, but the highest expression level was observed in the head kidney, followed by the spleen, intestine and peripheral blood leukocytes (PBLs). Furthermore, Southern blot analysis of the constant region of the IgM heavy chain gene of 3 different fishes indicated that Nile tilapia genomes may contain 2 copies of the IgM gene. Keywords: Nile Tilapia, IgM Heavy Chain, Variable Region, Diversity, Secreted Form, Southern Blot
Highlights
Nile tilapia (Oreochromis niloticus) is a freshwater fish that is cultured worldwide and is an important economic aquatic animal
Tissue expression profile analysis using quantitative real-time RT-PCR of healthy Nile tilapia showed that the IgM heavy chain gene was ubiquitously expressed in all 13 tested tissues, but the highest expression level was observed in the head kidney, followed by the spleen, intestine and peripheral blood leukocytes (PBLs)
The full-length cDNA was 1,921 nucleotides in length and composed of a 45-nucleotide 5’ untranslated region (UTR) that was followed by the open reading frame (ORF) beginning with ATG, the first translated codon
Summary
Nile tilapia (Oreochromis niloticus) is a freshwater fish that is cultured worldwide and is an important economic aquatic animal. In 2014, 174,872 tons were produced in Thailand as result of Phuyindee et al 2283 increased aquaculture throughout the country, ranging from earthen ponds to intensive cage-culture systems, making Thailand the 5th largest world tilapia producer (FAO, 2014) This activity has been promoted by related industries and supply chains, such as hatcheries, feed manufacturers and distributors, to support the huge domestic consumption. The bulk of fish deaths occurs due to protozoan, fungal and bacterial infections, typically due to Aeromonas hydrophila, Streptococcus agalactiae and Flavobacterium columnare, and result in lost tilapia yields in culture systems (Mohamed and Refat, 2011; Pridgeon et al, 2011; Rodkhum et al, 2011) To circumvent these problems, fish immunity must improve to increase the efficiency of disease prophylactic and therapeutic methods. An immunoglobulin molecule is composed of 2 heavy chains and 2 light chains that are joined by inter- and intradisulfide bonds
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
