Sequence Analysis Of VLDLR Gene And Study On It’s Polymorphisms And Association With Growth And Carcass Traits In Gaoyou Duck

The very low density lipoprotein receptor (VLDLR), a member of LDLR family, has an important role in metabolism of apoprotein-E-containing triacylglycerol-rich lipoproteins and is widely distributed in the most of tissues, including the heart, skeletal muscle, adipose tissue, and the brain, but is absent in the liver. In this study, the Gaoyou duck VLDLR gene was cloned by RT-PCR. The characteristics and structure of the VLDLR gene were analyzed or predicted on the basis of the bioinformatics. After the polymorphisms of the VLDLR gene were analyzed by sequencing, we correlate different dipotypes wtih duck growth traits and carcass traits. This research provides a theoretical basis for utilization of molecular markers in duck genetic breeding.1 Cloning and Sequence analysis of VLDLR gene in Gaoyou duckTo investigate the function of VLDLR gene in Gaoyou duck, the VLDLR cDNA gene amplified by RT-PCR and cloned from muscle tissue of Gaoyou duck, and then the bioinformatics of sequences were analyzed. The results showed that the VLDLR coding region was comprised of 2244 nucleotides and encoded 747 amino acid. The sequence was submitted to GenBank and the accession number is KP335149. The nucleotide similarity of Gaoyou duck VLDLR gene with hybrid duck, chicken, cattle, human, mus musculus, rabbit, rattus norvegicus, sus scrofa and danio rerio was 90.9%,84.5%,71.3%,73.3%,71.8%,72.1%,72.1%,71.7% and 63.2% respectively. The amino acid similarity of Gaoyou duck VLDLR gene with hybrid duck, chicken, cattle, human, mus musculus, rabbit, rattus norvegicus, sus scrofa and danio rerio was 93.7%,92.5%,77.9%,78.1%,78.7%,78.1%,77.9%,78.5% and 65.9% respectively. The VLDLR is a hydrophilic transmembrane protein which is comprised of several a-helixes, P-sheets and coils, with a extracellular region of 3 N-glyoosylation sites and 8 O-glyoosylation sites. VLDLR is a secretory protein, and the most possible cleavage site is predicted to occur between 36 and 37 amino acid by the analysis of signal peptide. This study laid foundations for further research on VLDLR gene expression, biological function and application in the production.2 Polymorphisms of VLDLR gene and it’s association with growth and carcass traits in Gaoyou duckIn order to study the genetic effects of polymorphisms in VLDLR gene on growth and carcass traits in Gaoyou duck, VLDLR gene polymorphisms were detected by DNA sequencing in 280 Gaoyou ducks. Eight single nucleotide polymorphism (SNP) loci, g.l67G>A, g.231C>T, g.243G>A, g.356-357 insCT, g.359delT, g.498C>T, g.563-564 insGA and g.631G>A were found. And g.231C>T and g.243G>A were located in coding region and were synonymous mutations, that is, the produced amino acid sequence is not modified. Genetic polymorphisms analysis showed that g.231C>T and g.356-357 insCT in male ducks and g.631G>A in female ducks had low polymorphism information content (PIC<0.25), the others had intermediate polymorphism information content (0.25<PIC<0.5). The Chi-square test indicated that g.498C>T and g.631G>A deviated from the Hardy-Weinberg equilibrium (P<0.05), the rest of SNPs were in Hardy-Weinberg equilibrium (P>0.05). Based on these eight SNPs, eight haplotypes were constructed by phase 2.0. H1 haplotype had the highest frequency in male and female ducks (>50%). The least-square analysis demonstrated that diplotype H1H2 had the highest 3-10 weeks body weight, carcass weight, semi-eviscerated weight, eviscerated weight, liver weight, abdominal fat weight, semi-eviscerated percentage, eviscerated percentage and abdominal fat percentage in males, H2H4 were the lowest. In female ducks, H3H4 had the highest 3-7 weeks body weight, carcass weight, semi-eviscerated weight and eviscerated weight. H1H2 had the highest 9-10 weeks body weight, liver weight, abdominal fat weight and abdominal fat percentage. H6H6 were the lowest. The results suggested that the VLDLR gene played an important role in the growth trait and adipose deposition of duck. This was the first report that the VLDLR gene could be a candidate gene influencing growth and carcass traits in duck.