Original research articleDifferential expression of six chicken genes associated with fatness traits in a divergently selected broiler population
Introduction
Chickens selected for rapid growth have an increased risk of physiological disorders such as obesity [1]. The excessive deposition of abdominal fat can lead to diseases such as ascites, leg malformation and sudden death syndrome in broiler chickens [2], [3]. Breeding chickens with less abdominal fat has become a goal of the poultry industry.
Genetic improvement of meat quality and carcass traits through traditional selection strategies is difficult because these traits have low or moderate heritability and, in general, can only be measured post slaughter [4], [5]. Abdominal fat is an important factor in meat quality and carcass traits in chickens. Efficient selection for improved meat quality and carcass traits through marker-assisted selection (MAS) or genomic selection using high-throughput genomic techniques is achievable. Genome-wide association studies (GWASs) are commonly used for the identification of genes responsible for complex traits in farm animals, which greatly facilitates MAS or genomic selection. GWASs have been used to identify major genomic loci associated with important economic traits in chickens [6].
In this study we have used a GWAS to identify a number of single nucleotide polymorphisms (SNPs) associated significantly with abdominal fat weight (AFW) and abdominal fat percentage (AFP) in chickens. Six significant SNPs located in the KDR, TUSC3, PPAT, EXOC1, MYBL2 and KIAA1211 genes were chosen to investigate whether these six genes affect the accumulation of abdominal fat via analysis of differential expression in abdominal fat and liver and by analysis of the correlation between the level of gene expression and AFW and AFP values.
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Experimental animals
The broilers used in this study were derived from the Northeast Agricultural University (NEAU) broiler lines divergently selected for abdominal fat content (NEAUHLF). The NEAUHLF line has been selected since 1996 using the AFP (abdominal fat weight/body weight) and the plasma very low-density lipoprotein (VLDL) concentration as selection criteria. The entire G0 generation of NEAUHLF came from the same Arbor Acres broiler grandsire line, which was then divided into two lines according to VLDL
Differential expression of the mRNA of six genes in abdominal fat and liver of two lines of chicken
As shown in Fig. 2, Fig. 3, all six genes were expressed in the abdominal fat and liver of the lean and fat lines. The same pattern of expression was observed when the internal controls GAPDH and β-actin were used as endogenous references. The results indicated that the level of mRNA expression of KDR was significantly (P < 0.01) higher in the abdominal fat and liver of the lean line than of the fat line. Furthermore, the expression level of TUSC3 in the liver of birds from the fat line was
Discussion
The qRT-PCR method is widely used when housekeeping genes act as the internal control in the calculation of accurate data normalization. In this study, it was necessary to use two reference genes to evaluate the accuracy and credibility [10], [11], [12], [13]. GAPDH and β-actin were used as the two endogenous reference genes and the same pattern of expression was observed, which enhanced the reliability of the results.
The differential expression of KDR mRNA between the two lines, coupled with
Conflict of interest
The authors declare that there is no conflict of interest.
Acknowledgments
The authors gratefully acknowledge the members of the Poultry Breeding Group at Northeast Agricultural University for help in managing the birds. This research was supported by the National 863 Project of China (No. 2011AA100301), Academic Backbone Project of Northeast Agricultural University (No. 15XG13), China Agriculture Research System (No. CARS-42) and the Program for Innovation Research Team in University of Heilongjiang Province (No. 2010td02).
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