June 2, 2016
The growth of long facial
feathers, creating the appearance of muffs and beards on chickens, is caused by
a chromosomal rearrangement affecting a gene involved in feather development,
report Xiaoxiang Hu of the China Agricultural University in Beijing and colleagues,
in a new study published on June 2 in PLOS Genetics.
Unusual plumage and fancy combs
aren't just interesting traits appreciated by poultry fanciers, but
opportunities to explore the genetics underlying these striking variations.
Scientists investigated the mutation that causes the Muffs and beard
characteristic in certain chicken varieties by mapping the trait to the correct
location on the chromosome and sequencing that region from chickens with and without
Muffs and beard. They found that chickens with the Muffs and beard trait 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 beard, but not in regular 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 linked to feather
development, such as HOXC8, which is associated with a crest of feathers on top
of the head. The findings present an excellent model for exploring the
regulation of HOX genes in different parts of the body during development.
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