Analysis of variations, structures, and phylogenic characteristics of bovine leukocyte antigen DRB3 exon2

Abstract

Bovine leukocyte antigen (BoLA) DRB3 is a highly polymorphic gene in major histocompatibility complex<br />(MHC) class II that plays a central role in immune responses and production factors. As of yet, molecular and<br />evolutionary characteristics of BoLA-DRB3.2* have not been as fully understood as human and mouse.<br />Therefore, we attempted to analyze variability and phylogeny of BoLA-DRB3.2* and illustrate some novel<br />practical evidence on interspecies diversity, the resistance /susceptibility points in cattle breeding, and vaccine<br />design. Initially, BoLA-DRB3.2* alleles and orthologous exons in the selected livestock were retrieved and<br />checked. In the next step, the secondary/tertiary structure of BoLA-DRB3.2*24 gene product was modeled and<br />validated. Then, hypervariable regions (HVRs) of alleles were identified by hybrid approaches. In the last step,<br />interspecies relationship, allele's phylogeny/grouping, and estimate of average evolutionary divergence were<br />explored. Shannon entropy variation analysis showed eight HVRs and three semi-variable regions in BoLADRB3.2*<br />alleles. These HVRs were present in all the three sub-structures and dominantly existed in alpha helix.<br />In addition, strong relationships and little diversity were noted in phylogenetic trees of cattle, buffaloes, sheep,<br />and goats. Furthermore, there was some evidence on divergence of DRB3 before speciation among the<br />mentioned species and possibility of cross prediction resistance/susceptibility alleles. Finally, DRB3 alleles were<br />grouped into seven clusters, and older and newer alleles were identified. The results show that similar studies<br />should be done in other animals to better understand the nature of the DRB3 attributes.