Polymorphism And Expression Analysis Of The Candidate Genes Influencing Feather Shape Trait On Chicken Chromosome 3

In order to figure out the difference between the silky and contour feather development, we applied the candidate gene clone strategy to hunt for the gene controlling the feather shape. The work in our lab indicated there is a potential locus controlling feather shape near ADL0115 marker on chicken chromosome 3, so BMP5, cEphA7 and Tbx18 near ADL0115 marker were chose as the candidate genes controlling feather shape.We detected polymorphisms and expression of the candidate genes in Silky and contour chicken at feather different development stages of feather. Then we analyzed the candidate genes association with the feather shape trait by the experimental results. In addition, we detected the expression of BMP5 in silky and contour chicken at different development stages from tissues, and analyzed its polymorphism sites associations with carcass traits in BMP5 gene. We try to discover the role of BMP5 gene on chicken carcass traits development.We detected the DNA variation of the whole coding region of BMP5, cEphA7, Tbx18 in Silky and Broiler by directing sequencing. The results showed that 1 SNP was detected in the exon 5 of Tbx18 gene. But no polymorphic site was detected in the whole coding region of BMP5 and cEphA7. However, the G→A transition at 789 bp in its transcript (NM204453, 1873 bp) resulted in no change to the amino acid substitution. In the F₂ chickens of 15 full-sib families, the frequency of the allele A and B are 92.5 % and 7.5 % respectively. In addition, we detected the DNA variation of the whole coding, 5' UTR, 3' UTR and partial intron region of BMP5 gene by PCR-SSCP in families. The results showed 3 SNPs were found in intron 1 and 1 SNP in intron 2. In intron 1 polymorphism sites, the allele A consists of 21041T, 21051A and 21134A, and allele B consists of 21041A, 21051T, and 21134C. In the F₂ chickens of 4 families, the frequency of the allele A and B are 29.15 % and 70.85 % respectively. For the mutation 5594T→5594C in intron 2 (5629 bp), the frequency of the allele T is 93.85 %, and the frequency of the allele C is 6.15 %. Based on the 4 SNP detected in BMP5 gene, four haplotypes were constructed and assigned H1, H2, H3 and H4. In F₂ population, there are six haplotypes H11, H12, H14, H22, H23 and H24 , the frequency of which is 6.1%, 41.4%, 3.3%, 40.9%, 1.1%, and 7.2% respectively. The least square analysis showed that H12, H22, H24 is significantly higher than Hllin eviscerated yield with giblet, eviscerated yield, Leg muscle weight, head and Wing weight et al. (p<0.05).We predicted that one transcription factor binding sites was inserted at 21041A in intron 1 with TFSEARCH program, and the least square analysis showed the mutation site associated with heart weight (p<0.1). Linkage analysis show that genetic positions of BMP5-IN1 and Tbx18-EX5 markers accord with phyisical positions of them, but they have little role on feather shape trait.By RT-PCR We detected the expression of the BMP5, cEphA7, Tbx18 gene on embryo 12 days, after-birth 1 day, 6 weeks, 9 weeks and 12 weeks in skin, and in 6 weeks and 9 weeks in feather follicle in Silky and contour chicken (White Leghorn and Broiler). The results showed no difference forexpression of BMP5 and Tbxl8 gene between Silky and contour chicken. And we detected the expression of BMP5 gene frome tissues at four stages such as embryo 12 days, after-birth 1 day, 6 weeks and 9 weeks. The results showed the products of BMP5 gene detected in all tissues, but the signal is weaker in spleen and small intestine.