The SNPs Of Chicken IGF2,IGFBP2 Gene Are Genetically Associated With Growth & Body Composition Traits

Although traditional selection depending on phenotypic value of broiler chicken has made significant improvement in growth rate during the past half century, poultry geneticists face additional challenges today because of negative correlation between production performance and fitness traits. Accompanying selection for rapid growth, meat-type birds exhibit an increase in physiological disorders such as obesity, ascites, sudden death syndrome, and leg problems, as well as a reduction in overall immunocompetency. Molecular marker-assisted selection may be required to increase selection efficiency. Genetic markers linked with QTL allow for direct selection on genotype. The combination of traditional genetic selection and modern molecular methods may be preferred for breeding chickens in the future.The biological effects of IGF2 are abroad, including effects on growth and differentiation of animal, and adipocyte precursor cell proliferation. In vivo, IGFBP2, being multifunctional binding protein, regulates the activity of IGF2 and TGF β , and affects the development of growth and fitness traits. Therefore, IGF2 and IGFBP2 genes can be viewed as the candidate genes that influence chicken growth and body composition traits. The objectives of the present study were to identify polymorphisms of IGF2 and IGFBP2 genes, develop PCR-SSCP methods to detect those DNA polymorphisms in the population of China native breeds, AA broiler and Hyline layer for population genetic analysis, in CAU F2 population and NEAU broiler lines divergent selection for abdominal fat for evaluating associations between IGF2 and IGFBP2 polymorphisms and traits of body composition and growth.(1)Two SNPs were found in coding sequence region of chicken IGF2 gene. Those are C139G(Accession No: S82962)in exon2 region, C943T in exon3 region. One SNP (C1196A, Accession No: U15086) was detected in 3'UTR region of IGFBP2 gene.(2)Population genetic analysis of SNPs in different breeds showed that: The frequency of genotypes (AA, AB, BB) caused by SNP of C139G were significant difference between each two breeds of BeijingYou, Shiqiza, Baier, Hyline layer, AA broiler (P0.05). To SNP of C1196A, the frequency genotypes (MM, MN, NN) were also significant difference between each two breeds of BeijingYou, Shiqiza, Baier, Hyline layer, AA broiler (P0.05).(3)There were significant associations between the C139G SNP and BW at 5 wk in CAU F2 population, AA genotype birds were significant lower than AB genotype birds (P<0.05); The difference of AFW, AFP between AB and BB genotype birds were significant (P0.05) inthe fifth NEAU broiler line. In the sixth NEAU broiler line, there were significant asssciations between the C139G SNP and CW/BW, GW (P0.05).There were significant associations between the C943T SNP and BW of new hatched, 7,8,9 wk, CW, LW in CAU F2 population (P0.05). The difference of BW of new hatched, CW between CC and CD genotypes were significant (P0.05). There were significant difference in BW of 7-9 wk, LW between CC and CD, DD genotype birds (P0.05).There were significant associations between the C1196A SNP and LW/BW in CAU F2 population, and there were significant difference between MM and MN genotype birds (P0.05). In the sixth NEAU broiler line, there were significant associations between the C1196A SNP and AFW, AFP, GW (P0.05). There were significant difference in AFW, AFP between MM and MN genotype birds (P0.05), in GW between MM and NN genotype birds.