Urial Genome Assembly Pinpoints Candidate Structural Variants Linked to Sheep Evolution

Researchers have generated a high-quality genome assembly of the Urial, an extant wild relative of domestic sheep, providing new genomic evidence regarding wild and domestic phenotypic divergence. By combining long-read Nanopore and short-read Illumina sequencing technologies, the team constructed an assembly spanning 2.57 gigabases with a contig N50 of 28.88 megabases. The assembly addresses a longstanding gap in sheep genomics, as the prior lack of a high-quality reference genome for Urial had constrained investigations into sheep domestication and evolutionary divergence.

Wild sheep possess distinct adaptive traits that make them valuable genetic resources for breeding programs aimed at improving domestic sheep stocks. Because Urial serves as an informative evolutionary model for understanding phenotypic changes across domestication, resolving its genomic sequence allows for systematic comparative analyses against established domestic sheep assemblies, such as the Rambouillet reference genome.

Through genome-wide analyses, the research team identified 735 expanding gene families alongside 56,691 structural variants across the assembly. By integrating the profiles of expanded gene families with the detected structural variants, the investigators isolated nine candidate genes potentially connected to body-size and evolutionary changes that occurred during the divergence of wild and domestic lineages.

Among these candidate loci, the study highlighted the ALDH1A1 gene, which was found to harbor a 117-base-pair sequence absent from the Rambouillet reference assembly compared to the newly assembled Urial genome. Subsequent functional analysis conducted in zebrafish models supported a potential biological role for the ALDH and retinoic acid pathway in vertebrate axial development.

The study authors concluded that these findings offer new candidate genomic mechanisms potentially associated with body-length evolution throughout sheep domestication history. Beyond the specific candidate genes identified, the completed assembly provides a foundational reference resource for future comparative genetic research and functional investigations exploring the genetic architecture of wild and domestic sheep breeds.

Subject of Research: High-quality Urial genome assembly and sheep evolutionary genetics

Article Title: High-quality genome assembly of Urial identifies candidate structural variants for sheep body-size evolution

Article References: Gao, Z., Lu, Y., Ma, R., Fu, Y., Wu, J., Wang, S., Esmailizadeh, A., Wu, D., Deng, W., & Chong, Y. (2026). High-quality genome assembly of Urial identifies candidate structural variants for sheep body-size evolution. BMC Genomics. https://doi.org/10.1186/s12864-026-13435-x

Image Credits: AI Generated

DOI: 10.1186/s12864-026-13435-x

Keywords: Urial, Ovis vignei, genome assembly, sheep evolution, domestication, structural variants, ALDH1A1, comparative genomics, Illumina sequencing, Nanopore sequencing, gene family expansion, axial development, retinoic acid pathway, body size evolution, wild sheep genetics