The Long & Short Of How Chickens Get Their Beards

Forget why the chicken crossed the road. Instead, how did the chicken get its beard?

AsianScientist (Jun. 10, 2016) – Ever wondered why some chickens have such magnificent, fluffy beards?

According to findings by Chinese scientists published in PLOS Genetics, the growth of long facial feathers on chickens is caused by a chromosomal rearrangement affecting a gene involved in feather development.

Unusual plumage and fancy combs aren’t just interesting traits appreciated by poultry fanciers, but opportunities to explore the genetics underlying these striking variations. Corresponding author Dr. Hu Xiaoxiang from the China Agricultural University in Beijing and colleagues set out to investigate the mutation that causes the muff and beard characteristic in certain chicken varieties.

They began by mapping the trait to the correct location on the chromosome and sequencing that region from chickens with and without muffs and beards. From this, they found that chickens with muff and beard traits had three duplicated regions of chromosome 27, inserted next to one of the original gene regions.

By examining changes in gene expression, they showed that one of the duplicated genes, HOXB8, which is known to function in feather development, was present at high levels in the facial skin of chickens with muffs and beards, but not in normal chickens.

The scientists suspect that HOXB8 expression may extend the growth phase of the facial feathers, creating the characteristic bearded appearance. Other HOX gene members are also linked to feather development, such as HOXC8, which is associated with growth of the crest of feathers on top of the head.

“Our findings show the significance for structural variations on phenotypic diversity and a novel role thatHOXB8 plays in feather formation. In future studies, we’ll focus on the regulation of HOX genes in feather cycles,” said first author, Dr. Guo Ying.

The article can be found at: Guo et al. (2016) A Complex Structural Variation on Chromosome 27 Leads to the Ectopic Expression of HOXB8 and the Muffs and Beard Phenotype in Chickens.


Source: PLOS; Photo: Guo Ying and colleagues.
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