A genomic duplication is associated with ectopic eomesodermin expression in the embryonic chicken comb and two...

Area of Science:

• Developmental biology
• Genomics
• Animal genetics

Background:

• Comb morphology in domestic chickens is influenced by major genetic loci.
• Duplex-comb (D) is one such locus, with V-shaped (D*V) and Buttercup (D*C) alleles.
• Understanding the genetic basis of these variations is key to avian genetics.

Purpose of the Study:

• To investigate the genetic underpinnings of the Duplex-comb locus in chickens.
• To identify the molecular mechanism causing the V-shaped and Buttercup comb phenotypes.
• To compare the Duplex-comb locus mechanism with other known comb morphology loci.

Main Methods:

• Association analysis of Duplex-comb alleles with genomic structural variants.
• Identification of conserved regulatory elements within the duplicated region.
• Analysis of eomesodermin (EOMES) gene expression in developing chicken embryos.

Main Results:

• Both D*V and D*C alleles are associated with a 20 Kb tandem duplication upstream of the EOMES gene.
• Ectopic expression of EOMES was observed in the ectoderm of the comb-developing region in D*V and D*C embryos.
• This contrasts with Rose-comb and Pea-comb loci, where ectopic expression occurs in the mesenchyme.

Conclusions:

• The Duplex-comb locus results from a large-scale structural genomic variant causing ectopic EOMES expression.
• Allele evolution in domestic animals can involve the accumulation of mutations on structural variants.
• Further research is needed to determine the order of mutations for D*V and D*C alleles.