Distribution of ancient α1 and α2 domain lineages between two classical MHC class I genes and their alleles in grass carp

AbstractMajor histocompatibility complex (MHC) class I molecules play a crucial role in the immune response by binding and presenting pathogen-derived peptides to specific CD8+ T cells. From cDNA of 20 individuals of wild grass carp (Ctenopharyngodon idellus), we could amplify one or two alleles each of classical MHC class I genesCtid-UAA andCtid-UBA. In total, 27 and 22 unique alleles ofCtid-UAA andCtid-UBA were found. The leader, α1, transmembrane and cytoplasmic regions distinguish betweenCtid-UAA andCtid-UBA, and their encoded α1 domain sequences belong to the ancient lineages α1-V and α1-II, respectively, which separated several hundred million years ago. However,Ctid-UAA andCtid-UBA share allelic lineage variation in their α2 and α3 sequences, in a pattern suggestive of past interlocus recombination events that transferred α2+α3 fragments. The allelic Ctid-UAA and Ctid-UBA variation involves ancient variation between domain lineages α2-I and α2-II, which in the present study was dated back to before the ancestra l separation of teleost fish and spotted gar (>  300 million years ago). This is the first report with compelling evidence that recombination events combining different ancient α1 and α2 domain lineages had a major impact on the allelic variation of two different classical MHC class I genes within the same species.

Source: Immunogenetics - April 1, 2019 Category: Genetics & Stem Cells Source Type: research