The Cloning, Expression And Polymorphism Of MHC Class â…¡ Gene From Three Marine Fishes

The major histocompatibility complex (MHC) is a group of closely linked loci present in remarkably similar form in all mammals and perhaps in all vertebrates. It is hetero-dimer gene encoding glycoprotein which presents peptides to T4 cell, and plays a central role in immune system. This research studied the cloning, expression, polymorphism and the associations between some genotypes and resistance ability of major histocompatibility complex (MHC) using the methods of PCR, RT-PCR, RACE and RFLP-Southern blot from three important marine fishes in our country, red sea bream, Japanese flounder and turbot, respectively. Our aim was to screen some MHCâ…¡B alleles associated with resistance in order to realize application of molecular markers in fish breeding.(1) In order to study function and molecular polymorphism of classâ…¡B gene in fish, we have isolated cDNAs encoding classâ…¡B from spleen cDNA library of red sea bream (Chrysophrys major) by using EST sequencing, and examined genomic organization, molecular polymorphism and expression of red sea bream classâ…¡B gene. As in other vertebrates, five exons and four introns were identified in red sea bream classâ…¡B gene. Seven classâ…¡B alleles were identified from seven individuals of red sea bream. The deduced amino acid sequence of red sea bream MHC classâ…¡B 1(Chma-DAB*0101) had 87.1%,85.1%,87.1%,90.4%,87.1%,90.8% identity with those of red sea bream classâ…¡B 2, 3, 4, 5, 6, 7(Chma-DAB*0201-Chma-DAB*0701), respectively, and had 75.2%, 74.5%, 55.9%, 55.1%, 34.3% and 30.4 % identity with those of striped sea bass, cichlid, rainbow trout, Atlantic salmon, mouse and human, respectively. Four different classâ…¡B alleles were observed in a single individual and two different 3'untranslated region...