Correlation between Single Nucleotide Polymorphism in 5' Regulation Region of IL-8 and Coccidiosis-Resistance of Jinghai Yellow Chicken

  Objective  Correlation between the single nucleotide polymorphism (SNPs) in the 5' regulation region of IL-8 and the disease resistance to Eimeria tenella of chickens was studied.

  Method  Direct DNA sequencing was performed to determine SNPs in IL-8 gene of Jinghai yellow chicken. Predicted transcription factors before and after mutation were analyzed to correlate between SNPs and coccidiosis-resistance of the birds.

  Result  There were 3 SNPs at the mutation sites of T-550C, G-398T and T-360C detected in the target region that formed CT-, TT- and GG-genotypes with heterozygous degrees between 0.436 and 0.471 and PIC between 0.25 and 0.5. In a Hardy-Weinberg equilibrium state, SNPs were moderately polymorphic. A bioinformatics analysis confirmed that the original transcription factor binding sites in the genes had all been altered after the mutation. The expression of IL-8 of TC-genotype mutated at T-550C was significantly higher than that of TT-genotype. The coccidiosis-resistance indicators including GSH-PX, CAT, IL-2, IL-6 and IFN-γ in TC-genotype were higher than that in the other two genotypes, though not significantly. In genotypes mutated at G-398T, the SOD activity of TT-genotype and the CAT activity of GT-genotype were significantly higher than those of GG-genotype; the NO content of TT-genotype extremely significantly different from that of GG-genotype and significantly different from that of GT-genotype; and, the IL-2 expression of TT-genotype significantly higher than that of GT-genotype. Whereas, in the genotypes mutated at T-360C, the SOD activities of TT- and TC-genotypes were extremely significantly different or significantly different from that of CC-genotype; the NO contents of TT- and TC-genotypes significantly higher than that of the CC genotype; and, the IL-2 and IL-8 expressions of the TT genotype significantly higher than those of CC-genotypes.

  Conclusion  It appeared that the TT-genotype with mutated G-398T or T-360C site would be more resistant to the parasitic attack by E. tenella than the other genotypes, and that hybrids of the genotypes carrying T-550C mutation would be more resistant than the homozygous counterparts. Thus, the significant regulation function of the polymorphism in the 5' regulation region of IL-8 gene could conceivably be targeted for breeding coccidiosis-resistant chickens.