Spatial and Temporal Expression Characteristics of the HBB Gene Family in Six Different Pig Breeds

SIMPLE SUMMARY: β-Thalassemia is one of the most prevalent inherited diseases in China. It is important to develop animal models to accurately simulate human β-thalassemia and there are unique advantages to studying β-thalassemia in pigs. However, there are only few reports on the systematic analysis of the β-thalassemia-related genes and their expression pattern in pigs so far. Therefore, in this study, we firstly predicted 11 porcine hemoglobin-encoding genes and found that there was no HBG gene in pigs, indicating that the globin switches might not exist in pigs. A new hemoglobin-encoding gene, ‘HBB-like’, was found in pigs, which showed high conservation in its amino sequences between pigs and humans. Then, we studied the evolutionary relationship of hemoglobin-encoding genes in human, pig and mouse. The results showed that the β-chain structure of pig and human was highly similar. In addition, we analyzed the hemoglobin-encoding gene expressions by using the iswine database and qPCR. Our results showed significant differences in the spatiotemporal expression patterns among the four genes (HBA, HBB, HBB-like and HBE) in three developmental stages of six different pig breeds. Our study provides an important theoretical basis for further construction of a gene-edited β-thalassemia miniature pig model to assess β--thalassemia treatments. ABSTRACT: β-Thalassemia induces hemolytic anemia caused by mutations in the β-chain gene locus. As humans progress from embryo to adulthood, hemoglobin recombines twice. To test whether similar hemoglobin reassembly occurs in pigs, bioinformatics tools were used to predict the pig hemoglobin-encoding gene. We then systematically analyzed the expression patterns of the HBB gene family in three developmental stages (weaning, sexual maturity and physical maturity) of six different pig breeds (Landrace, Yorkshire, Wuzhishan, Songliao black, Meishan and Tibetan). The results showed that the new hemoglobin coding gene ‘HBB-like’ was found in pigs, while the HBG gene did not exist in pigs, indicating that human-like reassembly might not exist in pigs. The HBB and HBB-like genes shared highly similar amino acid sequences and gene sequences. The genes on the β-chain were highly similar between humans and pigs and the amino acid sequences of human and pig HBB genes at position 26 and positions 41–42 were identical. qPCR results showed that there were significant differences in the spatiotemporal expression patterns of the four genes (HBA, HBB, HBB-like and HBE) across breeds. Our results provide a foundation for follow-up studies assessing the relationship between the gene-encoding hemoglobin and β-thalassemia disease, as well as the construction of a gene-edited β-thalassemia miniature pig model to assess β-thalassemia treatments.