Abstract
Diacylglycerol acyltransferase (DGAT) is a key enzyme that catalyzes the final and rate-limiting step of triglyceride synthesis. Both DGAT1 and DGAT2 genes code proteins with DGAT activity. Studies have shown DGAT1 polymorphisms associate with intramuscular fat deposition in beef cattle, but fewer associations between DGAT2 and beef cattle economic traits have been reported. The objective of this study was to investigate single nucleotide polymorphism (SNP) in intron3 of bovine DGAT2 and evaluate the associations of that with carcass, meat quality, and fat yield traits. Test animals were 157 commercial feedlot steers belonging to 3 Chinese native breeds (22 for Luxi, 24 for Jinnan, and 23 for Qinchuan), 3 cross populations (20 for CharolaisxFuzhou, 18 for Limousin xLuxi, and 17 for Simmental×Jinan) and 1 Taurus pure breed population (16 Angus steers). In the current study, 15 SNP were discovered in intron3 and exon4 of DGAT2 at positions 65, 128, 178, 210, 241, 255, 270, 312, 328, 334, 365, 366, 371, 415, and 437 (named as their positions in PCR amplified fragments). Only 7 of them (128, 178, 241, 270, 312, 328, and 371) were analyzed, because SNP in three groups (65-128-255, 178-210-365 and 241-334-366) were in complete linkage disequilibrium within the group, and SNP 415 was a deletion and 437 was a null mutation. Frequencies for rare alleles in the 3 native breed populations were higher than in the 3 cross populations for 178 (p = 0.04), 270 (p = 0.001), 312 (p = 0.03) and 371 (p = 0.002). A general linear model was used to evaluate the associations between either SNP genotypes or allele substitutions and the measured traits. Results showed that SNP 270 had a significant association with the fat yield associated with kidney, pelvic cavity, heart, intestine, and stomach (KPHISY). Animals with genotype CC and CT for 270 had less (CC: -7.71±3.3 kg and CT: -5.34±2.5 kg) KPHISY than animals with genotype TT (p = 0.02). Allele C for 270 was associated with an increase of -4.26±1.52 kg KPHISY (p = 0.006) and -0.92±0.45% of retail cuts weight percentage (NMP, Retail cuts weight/slaughter body weight) (p = 0.045); allele G for 312 was associated with an increase of -5.45±2.41 kg KPHISY (p = 0.026). An initial conclusion was that associations do exist between DGAT2 gene and carcass fat traits. Because of the small sample size of this study, it is proposed that further effort is required to validate these findings in larger populations.
Highlights
Triglycerides are the major energy storage molecules in eukaryotes
The present study discovered 14 new bi-allelic single nucleotide substitutions in intron3 of the bovine DGAT2 gene and 1 single nucleotide substitution in exon4
Our analyses revealed that intron3 single nucleotide polymorphisms (SNP) in 3 groups, were in complete linkage disequilibrium within SNP groups
Summary
Triglycerides are the major energy storage molecules in eukaryotes. The final, and presumably rate-limiting, step of triglyceride synthesis is catalyzed by a diacylglycerolLi et al (2009) Asian-Aust. Triglycerides are the major energy storage molecules in eukaryotes. The final, and presumably rate-limiting, step of triglyceride synthesis is catalyzed by a diacylglycerol. Other studies detected 15 SNP in intron of the bovine DGAT2 gene (Figure 1), which was found to be the most abundant polymorphisms among all 7 introns and 8 exons of DGAT2 (Xu et al, 2004). Several studies have reported associations between DGAT1 and economic traits of cattle (Spelman et al, 2002; Thaller et al, 2003; Winter et al, 2003b). There have been fewer reports on associations between DGAT2 and beef cattle traits. The objective of this study was to investigate single nucleotide polymorphisms (SNP) in bovine DGAT2 gene intron and evaluate the associations between SNP and slaughter body weight, carcass and meat quality, and especially fat yield traits in commercial feedlot populations of steers
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