An Illumina approach to MHC typing of Atlantic salmon.

The IPD-MHC Database represents the official repository for non-human major histocompatibility complex (MHC) sequences, overseen and supported by the Comparative MHC Nomenclature Committee, providing access to curated MHC data and associated analysis tools. IPD-MHC gathers allelic MHC class I and class II sequences from classical and non-classical MHC loci from various non-human animals including pets, farmed and experimental model animals. So far, Atlantic salmon and rainbow trout are the only teleost fish species with MHC class I and class II sequences present. For the remaining teleost or ray-finned species, data on alleles originating from given classical locus is scarce hampering their inclusion in the database. However, a fast expansion of sequenced genomes opens for identification of classical loci where high-throughput sequencing (HTS) will enable typing of allelic variants in a variety of new teleost or ray-finned species. HTS also opens for large-scale studies of salmonid MHC diversity challenging the current database nomenclature and analysis tools. Here we establish an Illumina approach to identify allelic MHC diversity in Atlantic salmon, using animals from an endangered wild population, and alter the salmonid MHC nomenclature to accommodate the expected sequence expansions.