Characterization of TCR ß-chain Locus genotypes of rainbow trout (Oncorhynchusmykiss) by SSCP analysis.
T cells play important regulatory roles in the immune responses of jawed vertebrates. In the present study T cell receptor (TCR) coding genes of the Rainbow trout (Oncorhynchusmykiss) as a main aquaculture species of Iranian cold waters was analyzed. So five farms of this species were selected in Harazriver and 50 fin sampleswere collected and screened for TCR ß chain locus with the single strand conformation analysis method. Results of this research indicated limited alleles number (3-6 alleles) with higher observed heterozygosity (75%) than expected heterozygosity (68%). In addition, results imply the effect of aquaculture farms effluent that increases the pollution of pathogens and abiotic materials with increase of allele numbers in next farms. These data could be very useful in immunogenetic assessment of aquaculture farms.
INTRODUCTION; Characterization of TCR ß-chain Locus genotypes of rainbow trout
T cells play important regulatory roles in the immune responses of jawed vertebrates. In mammals, TCRs are heterodimeric that consisting of either α/ß or γ/δ polypeptide combinations. The T cells are active when the heterodimer TCR on the surface of a T cell, specifically recognizes an externally presented Ag, in conjunction with the CD3 receptor complex . The structure and expression of genes encoding molecules homologous to mammalian αß TCR have been identified from almost all vertebrate classes, including birds , amphibians (Chretien et al, 1997), teleosts, and elasmobranches . However, γδTCR homologues have not been identified in teleosts. Even though, the molecular structure of TCR proteins, presumed from their cDNA sequences, is appropriately conserved in all vertebrates, althoug there is very little information on the genomic organization and the genetic loci that encode the TCR molecules in primitive vertebrates. With increasing the importance of aquaculture production and immunity considerations, the structural and genomic organization of TCR ß chain locus have been analyzed in different fish species such as horned shark  and the rainbow trout . Hence, the TCR α locus has been characterized in Japanese puffer fish (Takifugurubripes) with cosmidcolnes.
MATERIAL AND METHOD
Genomic DNA was extracted from the fin clips of 50 rainbow trout brood stocks of randomly selected three farms located in Harazriver, IRAN (figure 1). Alcohol preserved samples was used for DNA extraction according to standard phenol-chloroform procedures (Sambrook et al, 1989)
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