The Crest Phenotype in Domestic Chicken Is Caused by a 195 bp Duplication in the Intron of HOXC10

The crest phenotype in domestic chickens was found to be caused by a 195 bp duplication in the intron of the HOXC10 gene on chromosome 33, as revealed by whole-genome sequencing. This mutation led to ectopic expression of at least five HOXC genes in the cranial skin of crested chickens, resulting in the development of larger feathers on the head. A diagnostic test confirmed the presence of this duplication in all 54 crested chickens across eight breeds, while it was absent in 433 non-crested chickens from 214 populations. The mutation was necessary for the development of a large crest and susceptibility to cerebral hernia, as seen in Polish chickens, but not sufficient to cause herniation in breeds with a small crest, like Silkie chickens.