A ROR2 coding variant is associated with craniofacial variation in domestic pigeons

Area of Science:

• Evolutionary developmental biology
• Comparative genomics
• Quantitative genetics

Background:

• Vertebrate craniofacial development relies on conserved pathways, typically resulting in limited variation within species.
• Domestic pigeons show remarkable craniofacial diversity, particularly in beak length, driven by artificial selection.
• Previous studies suggested a few genetic factors, including a sex-linked locus (Ku2), regulate pigeon beak length.

Purpose of the Study:

• To identify the genetic basis of extreme craniofacial variation in domestic pigeons.
• To pinpoint the specific genetic locus and genes responsible for differences in beak morphology between pigeon breeds.

Main Methods:

• Geometric morphometrics and quantitative trait locus (QTL) mapping were employed using an F2 intercross population.
• Comparative genomic analyses were performed to identify differentiated loci between short- and medium-beaked breeds.
• Candidate gene analysis focused on the identified Z chromosome locus, specifically examining the ROR2 gene.

Main Results:

• A single quantitative trait locus (QTL) on the Z chromosome was identified, explaining a significant portion of beak morphology variation.
• This Z chromosome locus showed strong differentiation between pigeon breeds with distinct beak lengths.
• An amino acid substitution in the ROR2 gene within the identified locus was found to be a potential regulator of pigeon beak length.

Conclusions:

• The study identified a major Z chromosome locus regulating pigeon beak length, highlighting its role in craniofacial diversity.
• The ROR2 gene, implicated in non-canonical Wnt signaling, is a strong candidate for controlling pigeon beak morphology.
• Pigeon craniofacial variation provides a model for understanding genetic mechanisms underlying vertebrate craniofacial development and diversity.