Analysis Of The Genetic Mutations In MGAT Gene And Their Effect With Growth Traits In Cattle

The primary function of monoacylglycerol acyltransferase (MGAT) is that catalyze the synthesis of diacylglycerol from monoacylglycerol and so far three members of MGAT gene have been identified, and can be roughly divided into MGAT1, MGAT2 and MGAT3, respectively. MGAT genes as an important gene family for the synthesis of diacylglycerol, relates to dietary fat uptake, lipids synthesis, storage and intracellular signal transduction. Genetic variations of MGAT genes were detected by DNA pool sequencing, PCR-SSCP and PCR-RFLP techniques in 1145 individuals from five cattle populations (Jiaxian cattle, Nanyang cattle, Qinchuan cattle, Caoyuan cattle and Luxi cattle), and association analysis were carried out to evaluate the effects of genotypes of the candidate genes on growth traits of three Chinese cattle (Jiaxian Red cattle, Nanyang cattle, Qinchuan cattle). The objects were to discover the hereditary characteristics and to explore molecular markers with significant effects on growth traits for efficient selection and improvement of Chinese cattle, and for the protection and usage of breed resource of Chinese cattle, to provide genetic information for foundation of molecular marker database. The results were as follows:1. SNPs detection of MGAT1, MGAT2 and MGAT3 geneAll of the exons, partial introns, 5'UTR and 3'UTR in seventeen loci of MGAT1, MGAT2, MGAT3 were dected in JX, QC, NY, CY and LX cattle. In the six loci of MGAT1 gene, 3 mutations were detected and only one SNP was located in exon 4(MGAT1 m.509 C>G). The mutation of MGAT1 m.509 C>G locus resulted to Ser>Cys. In the six loci of MGAT2 gene, 9 mutations were detected and only two SNPs were located in the CDS. Analysis of the mutations, MGAT2 gene m.84 T>G locus resulted to Ile>Met and m.756 G>A locus belong to same sense mutation. In the five loci of MGAT3 gene, 25 mutations were detected and one SNP located in exon 1 and two SNPs located in exon 4 were detected. The mutations of MGAT3 gene m.229 G>A locus and m.664/665 C/A>T/G locus resulted to Gly>Ser and His>Cys, respectively.2. The polymorphisms of MGAT1, MGAT2 and MGAT3 gene and their association with growth traits in Nanyang, Qinchuan and Jiaxian Red cattleByχ2 test, the SNPs of MGAT1, MGAT2 and MGAT3 were not association with the growth traits in QC and JX breed. In NY breed, except the MGAT2 gene m.756 G>A locus was not association with the body weight and average daily gain. All of the mutations were association with body weight and average daily gain (P<0.05). For the m.509 C>G mutation of MGAT1 gene the CC genotype showed better body weight and average daily gain than the GG genotype. In MGAT2 gene m.84 T>G locus the TT genotype showed better body weight and average daily gain than the GG genotype. For the m.229 G>A locus of MGAT3 gene the CC genotype showed better body weight and average daily gain than the GG genotype, and in m.664/665 C/A>T/G locus the TC/GA genotype also showed better body weight and average daily gain than the TT/GG genotype.3. Bioinformatics analysis of MGAT geneThe protein sequence and structure of MGAT have been analysized. The results showed that the homologies of cDNA nucleotide sequence of MGAT1, MGAT2, and MGAT3 gene with the DGAT2 gene were closed. This meant that the MGAT gene in cattle also possessed DGAT activity. Moreover, MGAT1 gene and MGAT2 gene encoded 335 aa and 332 aa in Chinese cattle, respectively. Both of them contained a signal peptide, a strong hydrophobicity structure and two transmembrane domains. MGAT3 gene encoded 405 aa which had no signal peptide clearly, but contained a strong hydrophobicity structure and three transmembrane domains.