The Genetic Mechanism Of BCDO2 Mutations On Reg?lating The Shin Colour Of Broilers

Broiler production is among the pillar industries of national economy, also one of the pillar industries of our animal husbandry. It has great implication to study broiler genetics and breeding. With the improvement of living standards, customers prefer broilers with yellow or dark skin more and more.The dark skin was caused by melanosomes spreading under the skin, which was synthesised through a complex progress by the animal itself. The shallow skin, however, is caused by carotenoid depositing in skin, which could not be synthesized by an animal itself. Thus, 2 enzymes related to carotenoid are needed, BCMO1 and BCDO2. The first one is a key enzyme to synthesis Vitamin A,while the second one may not be relative to this process directly, it does deavage carotenoid asymmetrily into colourless products and result in white skin.Our study expended what have learned about BCDO2.BCDO2 of chicken located on chromosome 24, with 3 SNPs(G/A at 6264085,A/G at 6273428 and G/A at 6287900) related to yellow skin, according to a former report. In our study, we took the local broiler breedings of Shandong Province as samples to dig up more SNPs by studying the detail information of PCR amplication products. Also, we did some correlation analysis between the genotypes of each SNPs and the b* values. Besides, we studied the different expression levels of BCDO2 in different chicken tissues. Finally, we tried to test the methylation patterns of the CpG island of the promoter and to analyze the correlation between these two results.Here are the results. Except for the 3 known SNPs, 17 more SNPs were detected.SNP A and SNP B showed great insignificant relations with b* value of the shin,but nor SNP C.4 of these 21 SNPs were on intron 2, and 17 of them were on intron 9, while the rest 2 were on exton10. 9 of the total SNPs showed low polymorphism information content(PIC<0.25), and the rest showed middle polymorphism information content(0.25<PIC<0.5).The results of X2 showed that 6 of them fitted Hardy-Weinberg Equilibrium situation(P>0.05). Linkage disequilibrium occurred between many different SNPs sites, such as SNP 14 and SNP 17. By analyzing the expression levels of BCDO2 in different tissues of a heterozygote at SNP B, we found that the expression level in shin is significantly high than that in back, muscles, liver or overy. Furthermore, the results of methylation patterns on CpG island of the promoter showed that, the higher the methylation pattern is, the less the expresson level showed, which explained methylation on CpG island of the promoters restrained the gene expression level.It is important to go into the genetic mechanism of BCDO2 for at least 2 reasons. On the one hand, it helps fix the yellow shin in chicken breeding, on the other hand, it may be the key to answer the secrects of animal domestic and revolution.