Refining selection signals in dairy sheep using high-density genotyping data

Area of Science:

• Animal Genetics
• Evolutionary Biology
• Genomics

Background:

• Previous medium-density SNP chip analysis identified broad genomic regions under selection in Sarda and Valle del Belice sheep ecotypes.
• Focus on altitudinal adaptation, particularly in mountain ecotypes, necessitates validation and refinement of these candidate regions.

Purpose of the Study:

• To validate and refine candidate regions under selection using high-density genotyping data.
• To identify specific adaptive genes and variants in mountain sheep ecotypes.
• To investigate parallel adaptation mechanisms in different sheep breeds.

Main Methods:

• High-density genotyping of independent animal cohorts.
• Joint and between-ecotype comparative genomic analyses.
• Identification and characterization of genetic variants within candidate genes.

Main Results:

• Confirmed selection signals on specific chromosomes (19, X in Sarda; 3 in Valle del Belice).
• Identified candidate genes (e.g., KDM6A, KCNA5, KCNA6, GALNT8) linked to stress response, electrophysiology, and immune regulation.
• Refined selection signals in mountain ecotypes, revealing variants in genes related to neuroendocrine, cardiovascular, immune, and respiratory systems.

Conclusions:

• High-density data corroborate and refine previous selection signal findings.
• Identified genes and variants provide insights into multifaceted adaptations to mountainous environments.
• Convergent biological pathways suggest parallel adaptive evolution in Sarda and Valle del Belice sheep mountain ecotypes.