Genome-wide Association Study Of Aggressive Behavior In Chicken

In chicken, aggression is defined as a competition behavior for living space, food or spouse, and it can lead to appearance defects and increased mortality that causing decreasing productive profit in poultry production enterprise. In other hand, it is know that aggression that usually comes with crimes is a kind of bad action in human being. Animal aggression study benefited for the understanding of molecular mechanism of aggressive behavior related traits of human being.In the present study, in order to improve the breeding efficiency and reduce the aggression frequency of poultry production, we use Genome-wide association study(GWAS) method to identify the causative mutations or genes and genomic regions of aggressive behavior. The main results were as follows:(1) In order to recognize the relationship between aggression and body weight as well as feed intake, we recorded the these three traits of Chinese native dwarf yellow chicken male population from 67 to 82 day-old. The result of correlation analysis show that there was significant positive correlation(P = 8.66E-05) between DAF and DFI, but there is no significant correlation between daily aggressive frequency(DAF) and daily body weight(DBW)(P = 0.5787), and between DAF and daily body weight gain(DBWG)(P = 0.7104). It is suggest that aggressive behavior will give rise to decreasing of feed conversion rate.(2) To identify the quantitative trait loci(QTLs) of aggressive behavior, we performed GWAS using 600 K Affymetrix Axiom HD genotyping array in a Chinese native dwarf yellow chicken population. The result shown that a total of 105 SNP effects(including 62 different SNP markers) reach suggestive significance(P < 4.6E-6), and 17 of them(including 8 different SNP markers) reached 5% Bonferroni genome-wide significance(P < 2.3E-7). A cluster of SNP was found to locate at the SORCS2 gene on chromosome 4, with the strongest association for rs312463697(P = 7.78E-09).(3) q PCR showed that SORCS2 is significantly up-regulated in aggressor chicken compared with the control(P = 0.029) in pituitary tissue.(4) Biological function analysis of the nearest genes(30 genes) around the significant SNP was performed with Ingenuity Pathway Analysis. The result output 2 networks and the most significant network contained 35 genes, including 11 eligible genes. The major function of this network contains cellular compromise, neurological disease, organismal injury, behavior and so on. SORCS2 was involved in this network, directly interacted with the nerve growth factor(NGF) gene.(5) Dopamine system was demonstrated to be linked with aggression in various species. After knockdown of SORCS2 by si RNA, the m RNA levels of NGF and dopamine receptor genes were significantly decreased(P = 0.003, 0.012, 1.64981E-05, 0.045, and 6.67515E-05 for NGF, DRD1, DRD2, DRD3 and DRD4, respectively).In summary, our data indicated that SORCS2 might play an important role in chicken aggressive behavior.