Comparative evolutionary analyses of beta globin gene in eutherian, dinosaurian and neopterygii taxa.

Background & Objectives: Comparative genomics and evolutionary analyses of conserved genes have enabled us to understand the complexity of genomes of closely related species. For example: β-globin gene present in human hemoglobin is one such gene that has experienced many genetic changes in many related taxa and produced more than 600 variants. One of the variant, HBS causes sickle-cell anemia in humans but offers protection against severe malaria due to Plasmodium falciparum. In the present study, we characterized and performed evolutionary comparative analyses of the ?-globin gene in different related and unrelated taxa to have a comprehensive view of its evolution.
Methods: DNA and protein sequences of β-globin gene were downloaded from NCBI and characterized in detail in nine eutherian (Homo sapiens, Pan troglodytes, Macaca mulatta, Mus musculus, Rattus norvegicus, Bos taurus, Canis familiaris, Equus caballus, Oryctolagus cuniculus), a dinosaurian (Gallus gallus) and a neopterygii (Danio rerio) taxa. Three more eutherian (Papio anubis, Ovis aries and Sus scrofa) taxa were included for an analysis at the protein level but not included at the gene level owing to lack of genomic information. Computational and phylogenetic analyses were performed using evolutionary comparative approach.
Results: Results of comparative and phylogenetic analyses revealed less conservation of genetic architecture of β-globin compared to its protein architecture in all eutherian taxa. Both dinosaurian and neopterygii taxa served as outgroups and varied at gene and protein levels.
Interpretation & Conclusion: Most remarkably, all primates from eutherian taxa including P. anubis showed only nine codon position differences and an absolute similarity between H. sapiens and P. troglodytes. Absolute conservation of coding region in Equus caballus (horse) was observed. The results were discussed with an inference on the role of evolutionary forces in maintaining such close similarities and variations across closely related taxa. Further, the need to utilize more comparative approaches in understanding the disease causing genes' evolution in closely related taxa is hoped for.