Identification of a 13 bp indel polymorphism in the 3′-UTR of DGAT2 gene associated with backfat thickness and lean percentage in pigs

• A 13 bp indel polymorphism exists at 905 bp downstream from the stop codon of porcine DGAT2 gene.
• Allele A is dominant in Yorkshire, Landrace, Duroc, Lulai Black, Laiwu, Dapulian and Junmu No.1 white pig breeds.
• Allele B carrying the 13 bp fragment has positive effect on backfat thickness and DGAT2 expression.
• DGAT2 mRNA expression in the backfat tissue of pigs with genotype BB was significantly higher than AB.

DGAT2 (acyl-CoA: diacylglycerol acyltransferase, EC2.3.1.20) is a member of acyl-CoA: monoacylglycerol acyltransferase (MGAT) family, which catalyzes one fatty acyl-CoA and diacylglycerol (DG) molecule to form triacylglycerols (TG) and is the final and rate-limiting step in the reaction of TG synthesis pathways. We previously showed that, during pig development, the fold change of DGAT2 mRNA in backfat tissue is much higher than that of DGAT1, implying that DGAT2 is more important in regulating porcine fat deposition. In this study, a 13 bp indel polymorphism located at 905 bp downstream from the stop codon (TGA) of porcine DGAT2 was found and two alleles of A (with 13 bp insertion) and B (no insertion) were designated. Allele A is dominant in all pig populations investigated. The backfat thickness of individuals with genotype AA is significantly lower than those with genotype AB (p < 0.01), and the lean percentage of individuals with genotype AA is significantly higher than those with genotype AB (p < 0.05) in Junmu No. 1 white pig population. The secondary structure of 3′-UTR without the 13 bp insertion is slightly less stable than with the 13 bp insertion type. In vitro assay indicates that, after differentiation, the luciferase activity was significantly higher for pGL3-B compared to pGL3-A vector (p < 0.001). Moreover, the DGAT2 mRNA expression in the backfat tissue of pigs with genotype BB was significantly higher than AB in commercial DLY pigs (p < 0.05). These results suggest that the 13 bp indel polymorphism in the 3′-UTR of porcine DGAT2 most likely affects fat deposition by altering its expression in pigs.