Yak DGAT1 gene: Cloning, tissue expression profile, splicing and polymorphism analysis

The objective of the present study was to reveal the characteristics of diacylglycerol O-acyltransferase 1 (DGAT1) gene of high altitude yak (Bos grunniens). Two mRNA sequences of yak DGAT1, including a full length and a spliced isoform deleted with 66 nucleotides in exon VIII, were cloned from Jiulong yak liver by reverse transcription polymerase chain reaction (RT-PCR). The coding sequence (CDS) of yak full length DGAT1 gene is 1470 bp, sharing 99.5% of nucleotide sequence homology and 100% of amino acid sequence homology with those of cattle, respectively. PCR analysis using DNA and RNA as templates demonstrated the alternative splicing of yak DGAT1 gene and estimated the proportion of the spliced isoform as approximately 30% of the total DGAT1 mRNA in yak liver and biceps femoris. Quantitative real-time RT-PCR analysis showed that both adult yak and cattle had significantly higher DGAT1 mRNA level in liver and adipose tissue than in skeletal muscles (P < 0.05), while no difference was observed between the corresponding tissues of yak and cattle, suggesting that yak DGAT1 gene might not be responsible for the lower intramuscular fat content in yaks compared to cattle. Allelic variation at nucleotide positions 10433 and 10434 (K232A) of the DGAT1 gene of yak and cattle was detected by polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) method. Nearly all yaks (n = 81) examined were homozygous for the K allele, while Chinese Holstein cows showed high frequency for the A allele. The K allele of yak DGAT1 gene might be correlated with its higher milk fat content characteristic.