Sequence diversity of the MHC Ⅱ DRB gene in Chinese tree shrews (Tupaia belangeri chinensis)

•Our work is the first study of MHC variation in a Chinese tree shrew population.•We identified 12 different DRB exon 2 alleles from 15 Chinese tree shrews.•Each individual has 1 to 4 allele with high level of sequence divergence.•The DRB exon 2 in Chinese tree shrews has been influenced by positive selection.•It provides a foundation for immunogenetic research of the Chinese tree shrew.

The major histocompatibility complex (MHC) is a cluster of genes involved in vertebrate immune response regulation. MHC class I and II cell surface proteins are crucial for discrimination of self versus non-self by the adaptive immune system. Due to their special phylogenetic position within the Euarchontoglires and as a relative of primates, tree shrews have been proposed as an alternative experimental animal model for biomedical studies. However, information about the genetic structure of the tree shrew populations is largely unknown. In this study, we characterized diversity in exon 2 of the MHC II DRB gene isolated from Chinese tree shrews (Tupaia belangeri chinensis). We identified 12 different DRB exon 2 alleles from 15 Chinese tree shrews, 1 to 4 alleles were observed per individual with high levels of sequence divergence between alleles. There were more non-synonymous than synonymous substitutions in the functionally important antigen-binding site (dN/dS = 2.7952, P < 0.01), indicating that the DRB exon 2 in Chinese tree shrews has been influenced by positive selection.