Molecular Characterization of MHC Class I Genes in Four Species of the Turdidae Family to Assess Genetic Diversity and Selection.

Muhammad Usman Ghani,Li Bo,Xu Yanchun,An Buyang,Muhammad Yasir,Shakeel Hussain

doi:10.1155/2021/5585687

Abstract

In vertebrate animals, the molecules encoded by major histocompatibility complex (MHC) genes play an essential role in the adaptive immunity. MHC class I deals with intracellular pathogens (virus) in birds. MHC class I diversity depends on the consequence of local and global environment selective pressure and gene flow. Here, we evaluated the MHC class I gene in four species of the Turdidae family from a broad geographical area of northeast China. We isolated 77 MHC class I sequences, including 47 putatively functional sequences and 30 pseudosequences from 80 individuals. Using the method based on analysis of cloned amplicons (n = 25) for each species, we found two and seven MHC I sequences per individual indicating more than one MHC I locus identified in all sampled species. Results revealed an overall elevated genetic diversity at MHC class I, evidence of different selection patterns among the domains of PBR and non-PBR. Alleles are found to be divergent with overall polymorphic sites per species ranging between 58 and 70 (out of 291 sites). Moreover, transspecies alleles were evident due to convergent evolution or recent speciation for the genus. Phylogenetic relationships among MHC I show an intermingling of alleles clustering among the Turdidae family rather than between other passerines. Pronounced MHC I gene diversity is essential for the existence of species. Our study signifies a valuable tool for the characterization of evolutionary relevant difference across a population of birds with high conservational concerns.

Highlights

The major histocompatibility complex (MHC) is a group of molecules encoded by certain genes that are most polymorphic to have been described in vertebrates’ genomes [1]
MHC class II molecules are heterodimers consisting of an α chain and a β chain; both contribute to presenting peptides from the processing of extracellular pathogens such as bacteria to the CD4+ T-helper cells [2]
Overall we find an elevated genetic diversity (π) within exon 3 alleles repertoire among individuals of Turdus atrogularis was (0.151) than Turdus eunomus (0.113)

Summary

Introduction

The major histocompatibility complex (MHC) is a group of molecules encoded by certain genes that are most polymorphic to have been described in vertebrates’ genomes [1]. Two types of MHC gene families, class I and class II, are useful to cell surface glycoproteins that regulate the immune response. MHC class II molecules are heterodimers consisting of an α chain and a β chain; both contribute to presenting peptides from the processing of extracellular pathogens such as bacteria to the CD4+ T-helper cells [2]. The MHC class I molecules are expressed in almost all somatic cells and trigger an adaptive immune response by presenting endogenously derived peptides of viral protein and an individual’s own body cells to CD8+ cytotoxic T-cells [4]. Polymorphism is largely confined within the region encoding the ABS (antigen-binding site) of MHC class I [5]. In an individual possessing huge numbers and diverse MHC alleles; more pathogens can be recognized [1]

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