Horpa sheep, an indigenous breed native to the high-altitude regions of the Xizang Autonomous Region in China, have long been valued for distinctive adaptive and economic traits. Yet until now, little was known about where they came from or which parts of their genome might underpin their ability to thrive at extreme elevations. A new genomic study published in BMC Genomic Data examines the breed's population structure and candidate signatures of selection, addressing ancestry and genetic questions that had previously remained unknown.

To place these animals in a broader genetic context, they combined their newly generated whole-genome resequencing data with publicly available genomes from 44 individuals representing other sheep populations. This comparative framework allowed the researchers to ask two linked questions: how closely related Horpa sheep are to neighbouring breeds, and whether specific genomic regions show the statistical fingerprints left by natural selection.

The population structure analysis revealed that Horpa sheep are genetically homogeneous as a breed, meaning the sampled animals share a relatively uniform genetic background. The analyses also uncovered a close phylogenetic relationship between Horpa sheep and Gansu Xizang sheep. According to the authors, this affinity may reflect shared ancestry, historical migration between the populations, and the geographic isolation imposed by the rugged high-altitude landscape they inhabit.

To detect signatures of selection, the team applied five complementary methods: the composite likelihood ratio (CLR), the integrated haplotype score (iHS), the population differentiation index (FST), the nucleotide diversity ratio (θπ ratio), and cross-population extended haplotype homozygosity (XP-EHH).

The most compelling candidates were genes flagged consistently across all five methods. Among them was MITF, described by the authors as a key regulator of pigmentation and protection against ultraviolet radiation. The second was ACSL6, which the authors note participates in lipid metabolism and energy homeostasis.

Beyond individual genes, the study identified candidate genomic regions enriched for quantitative trait loci, or QTLs, associated with production traits, particularly body weight.

The authors are careful to frame these results as candidate evidence rather than proof of function.

Even so, the study fills a real gap. Whole-genome resequencing and comparative analyses of different sheep populations have been performed elsewhere, but the ancestry and genetic basis underlying the adaptation of Horpa sheep had remained unknown. By combining locally sampled genomes with public data, the team has produced candidate genomic evidence for understanding the putative high-altitude adaptation and local population divergence of Horpa sheep.

The practical implications extend beyond evolutionary curiosity. The authors argue that their findings provide a useful framework for the strategic conservation and breeding of Horpa sheep.

Subject of Research: Population genomics and selection signatures in Horpa sheep from the Xizang Autonomous Region

Article Title: Population structure and signatures of selection in Horpa sheep

Article References: Zhaxi, Y., Song, T., Wu, Y., Deqing, Z., De, J., Gesang, J., Ren, Y., Zhang, L., & Suo, L. (2026). Population structure and signatures of selection in Horpa sheep. BMC Genomic Data. https://doi.org/10.1186/s12863-026-01487-7

Image Credits: AI Generated

DOI: 10.1186/s12863-026-01487-7

Keywords: Horpa sheep, Xizang, high-altitude adaptation, whole-genome resequencing, selection signatures, MITF, ACSL6, population structure, QTLs, sheep genetics, BMC Genomic Data, livestock conservation