Major histocompatibility complex genomic investigation of endangered Chinese alligator provides insights into the evolution of tetrapod major histocompatibility complex and survival of critically bottlenecked species

Background The major histocompatibility complex (MHC) gene family, a vital immune family in vertebrates, helps animals defend against pathogens. polymorphism of MHC genes is important for species and considered to be caused by the numerous alleles antigen-presenting genes. However, mechanism this process unclear due lack data on structure. evolutionary trajectories tetrapod are also because insufficient studies reptile architecture. Here, we studied Chinese alligator ( Alligator sinensis ), which experienced population bottleneck, but increased rapidly past 30 years proposed have unique system face pathogenic challenges. Results We successfully constructed 2 Mb region using bacterial artificial chromosome (BAC) library genome checked transcriptome rapid amplification cDNA ends (RACE) technique. architecture reported here uncovers adjacent Class I II subregions CD1 subregion. This newly added information suggested that I-II structure pattern was more ancient tetrapods helped reconstruct evolution found multiple groups class (MHC-I) (12 duplicated loci, belonging three groups, two were novel) (MHC-II) (11 groups) inside region, there MHC-I loci outside it. These highly had differences expression, amino acid length exons, splice signal exon intron, together promoted Although identified as monomorphic or oligomorphic our previous study, with high copy numbers many can make up loss, presenting another antigen presentation. MHC-IIB low each locus, all, may contribute binding variability population. Conclusion To summarize, fine reptiles presented study completes tetrapods, these distinctive expand recent years.