Ear type in sheep is associated with the MSRB3 locus.

Area of Science:

• Animal Genetics
• Sheep Breeding
• Genomics

Background:

• Ear morphology, including size and erectness, is a significant trait differentiating sheep breeds.
• This trait is understood to have a complex, polygenic inheritance pattern.
• Understanding the genetic basis of ear morphology aids in breed characterization and conservation.

Purpose of the Study:

• To conduct a genome-wide association study (GWAS) to identify genetic regions influencing sheep ear morphology.
• To investigate the genetic architecture underlying variation in ear size and erectness across diverse sheep breeds.
• To pinpoint specific genes and variants associated with distinct ear phenotypes.

Main Methods:

• Genome-wide analysis of 515 sheep from 17 breeds using 34k SNP genotyping data.
• Genome-wide association studies (GWAS) for ear size and erectness traits.
• Whole-genome resequencing and fine-mapping of candidate regions around the MSRB3 gene.

Main Results:

• A significant association for ear morphology was detected on ovine chromosome 3, linked to the MSRB3 gene.
• Alleles associated with the GWAS signal were more common in sheep exhibiting large and/or floppy ears.
• Whole-genome resequencing ruled out major copy number variants but fine-mapping indicated the causal variant is likely downstream of MSRB3.

Conclusions:

• The MSRB3 gene region on ovine chromosome 3 is strongly associated with sheep ear morphology, particularly large and floppy ears.
• While MSRB3 is implicated, the precise causal variant for large floppy ears appears to be located in a 175 kb region downstream of the gene's coding sequence.
• Further fine-mapping is required to identify the specific causal variant influencing ear size and shape in sheep.