Gene Mapping And Candidate Gene Expression Analysis For Dermal Hyperpigmentation Loci In The Chicken

Dermal hyperpigmentation is a unique character in a few chicken breeds, such as Silkie, which is extensive pigmentation in various internal tissues. It has been known that the dermal hyperpigmentationis controlled by2genes, autosomal dominant fibromelanosis （FM） and the sex-linked incompletely dominant inhibitor of dermal melanin （ID）. ID has the epistatic recessiveness to FM. The dermal hyperpigmentation will occur only when the id+and Fm gene concurrences in the same chicken. To fine mapping the FM and ID gene and learn the mechanism of they impact the dermal hyperpigmentation, this research developed2separate mapping populations to allow for the individual segregation of each gene. The fine mapping was made by gene-typing, linkage analysis. Then we analysed the structure of target area and the expression patterns of target genes.Though analysed the data of gene-typing, the FM showed significant association to the region of9,400,989bp-11,758,733bp,2,357,744bp length. There are two SNPs, Gga_rs16172768, Gga_rs16172722located at this segment. We found the genotype of these two SNPs is always heterozygote in all dermal hyperpigmentation chicken breeds. This phenomenon is obviously not accord with Mendel’s regularity of segregation, and prompts the possibility of CNVs existence in the region of these two SNPs. By aCGH analysis, two CNVs were confirmed on Chr20:10,718,139-10,844,289bp;11,263,937-11,435,137bp. Then we revealed the exact coordinates of the first duplicated region to be10,717,294-10,846,232bp; the coordinates of the second duplicated region to be11,262,904-11,435,256bp and conjectured the possible spatial arrangements of the duplicated regions. By detect the copy number of functional genes in CNV region, such as EDN3, SLMO2, ATP5e, TUBB1, the expression level of these genes and EDN3downstream gene EDNRB2, TYRP2, we proved the duplication of EDN3is the primary driver of FM.In ID population, the ID was highest association with ChrZ:71,945,632-73,291,823bp. After blasted the ChrZ to the new chicken ChrZ sequence （2010）, the expressions of10genes in the association region were detected. In the sample of Silkie and White Leghorn, the expression of CDKN2B has significant difference at E1.5d. The expression of MTAP, ALDH7A1, FEM1C was higher in White Leghorn before ElOd and higher in Silkie after E10d. By consider the function of these genes, we conjectured the MTAP to be the most probable gene for ID.Then we got three SNPs:ChrZ₈0762601（A/G）, ChrZ₈0813721（T/C）, ChrZ₈1683233（A/T） specific located in Silkie, JinHu chicken, GuShi chicken. They will be used for the more accurate analysis about ID.