Skin regional specification and higher-order HoxC regulation

Area of Science:

• Developmental Biology
• Evolutionary Genetics
• Molecular Biology

Background:

• The integument's role in adaptive structures like feathers and scales is crucial.
• Molecular mechanisms underlying integumentary appendage diversity remain largely unknown.
• Craniofacial integument exhibits significant diversity, with examples like the Polish chicken's crest feathers.

Purpose of the Study:

• To investigate the molecular basis of craniofacial integument diversity.
• To understand the role of gene regulation in the evolution of avian appendages.
• To identify genetic factors contributing to the Polish chicken's unique feather structure.

Main Methods:

• Micro-C analysis to study chromatin conformation.
• CRISPR-Cas9 gene editing to assess the function of a specific DNA duplication.
• Comparative sequence analysis to determine the evolutionary conservation of the identified sequence.

Main Results:

• A 195-base pair duplication in the HoxC10 intron of Polish chickens causes homeotic transformation of comb-to-crest feathers.
• The duplication leads to an open chromatin conformation in the HoxC-containing topologically associating domain (TAD) in the scalp, increasing HoxC expression.
• Deletion of the duplication reduces crest feather formation, and HoxC misexpression alters feather shape.

Conclusions:

• Higher-order regulation of the HoxC cluster modulates gene expression.
• This regulatory mechanism drives the evolution of adaptive integumentary appendages in birds.
• The 195-bp sequence is specific to Archelosauria, suggesting a role in avian evolution.