Copy number variation inHOXB7andHOXB8involves in the formation of beard trait in chickens

The derived feathering phenotype beard in domestic birds is an ideal resource to investigate the genetic mechanisms controlling feather development and differentiation. In the present study, we performed a GWAS and QTL linkage analysis on the trait of beard in Beijing fatty chicken. One major QTL (1.2-1.9 Mb) was identified that could explain 34% of the phenotypic variation. The copy number variation that was copied from the region (GGA27:3 578 409-3 592 890 bp) containing homebox B7 (HOXB7) and homebox B8 (HOXB8) was validated to be only exhibited in the genome of bearded chickens. Protein-protein interaction analysis indicated thatHOXB7andHOXB8proteins could highly interact with the HOXB family members, includingHOXB4,HOXB5andHOXB6, whose genomic locations nearHOXB7andHOXB8suggested that they may regulate their family members to involve in the formation of the beard trait in chickens. Overall, our work provides basic data for understanding the mechanisms regulating beard development and differentiation.