Association between KAT2B gene polymorphisms and growth traits in Xiangsu hybrid pigs

【Objective】To understand the expression level of K（lysine）acetyltransferase 2B（KAT2B） gene in the tissues of Xiangsu hybrid pigs, to select the single nucleotide polymorphism（SNP） site of Xiangsu hybrid pigs, and to analyze the association between gene polymorphism and growth traits, so as to provide reference for breeding new Xiangsu hybrid pigs. 【Method】Xiangsu hybrid pigs were selected as the study object. Real-time fluorescence quantitative PCR was used to detect the relative expression of KAT2B gene in different tissues of 3 days and 6 months of age, and the SNP sites of KAT2B gene were detected by direct sequencing. Allele frequency, genotype frequency, heterozygosity（Ho）, expected heterozygosity（He）, effective allele number（Ne） and average peptide information content（PIC） of SNP sites were measured. Chi-square test （χ²） was used to analyze whether the genotypes were in Hardy-Weinberg equilibrium state. Then analyzed the relationship between different genotypes and growth traits of Xiangsu hybrid pigs. 【Result】Realtime fluorescence quantitative PCR results showed that KAT2B gene was expressed in 6 tissues of heart, liver, spleen, lung, kidney and longissimus dorsi muscle. Compared with 3 days of age, the relative expression level of liver and spleen was extremely significantly increased（P＜0.01, the same below）, while the relative expression level of lung was extremely significantly decreased. Exon-2, Exon-14 and Exon-15 regions in KAT2B gene had one exon mutation, which were g.36682G＞A, g.104540G＞T and g.106651A＞ G, respectively. All the three SNPs sites were in moderate polymorphism level and Hardy-Weinberg equilibrium. The dominant genotype of g.36682G＞A site was GA type, and the allele frequency G＞A; the dominant genotype of g.104540G＞T site was GG genotype, and the allele frequency G＞T; the dominant genotype of G. 106651A＞G site was AA, and the allele frequency was A＞G. The results of association analysis showed that there was no significant difference between genotype and growth traits of g.36682G＞A sites（P＞0.05）, and there was significant difference in chest depth between AA genotype and AG genotype at g.106651A＞G（P＜0.05）. 【Conclusion】The KAT2B gene is expressed in all tissues of Xiangsu hybrid pigs and there are three SNPs sites（g.36682G＞A, g.104540G＞T and g.106651A＞G）, KAT2B gene can be used as a candidate gene related to growth traits of Xiangsu hybrid pigs.