# Selection Signatures in the Genome of Dzhalgin Merino Sheep Breed

## TL;DR

This study identifies genes in Dzhalgin Merino sheep that may be responsible for their high productivity and adaptability to harsh environments.

## Contribution

The study discovers 185 genes, including key candidates, in Dzhalgin Merino sheep under selection pressure for adaptive and productive traits.

## Key findings

- A total of 185 genes were identified in loci showing evidence of selection in Dzhalgin Merino sheep.
- Seven genes (EPHA6, MLLT3, ROBO1, KIAA0753, MED31, SLC13A5, and ELAVL4) were highlighted as key candidates for further research.
- The identified genes are potentially involved in growth, development, and reproduction processes.

## Abstract

Selection acting on farm animal populations results in the formation of specific regions in their genomes that reflect the influence of the selection process. Studying such regions allows us to identify genes and genetic variants that play a key role in animal adaptation to environmental conditions and in the formation of productive traits. The Dzhalgin Merino breed was bred in Russia relatively recently and is characterized by high meat and wool productivity, as well as good adaptability to arid steppe conditions. Given the genetic closeness of this breed to the Australian Merino and Rambouillet, the aim of this study was to search for selection signatures and identify candidate genes at loci under selection pressure based on a comparative analysis of the Dzhalgin Merino genomes with Australian Merino and Rambouillet sheep. The identified genes are potentially involved in the formation of adaptive and productive traits significant for this breed. In total, 185 genes were identified in loci showing evidence of selection. Among them, EPHA6, MLLT3, ROBO1, KIAA0753, MED31, SLC13A5, and ELAVL4 were highlighted as the most promising candidates for further research, due to their association with biological processes such as growth, development, and reproduction.

Analysis of selection signatures in the genomes of farm animals enables the detection of genomic regions affected by selection and contributes to the identification of genes underlying adaptive and productive traits. This research aimed to identify loci under selection pressure and to detect candidate genes in Dzhalgin Merino sheep by performing a comparative genomic analysis with the related Australian Merino and Rambouillet breeds. A total of 293 animals were included in the analysis, comprising Dzhalgin Merino (n = 53), Australian Merino (n = 50), Australian Industry Merino (n = 88), and Rambouillet (n = 102). Whole-genome SNP genotyping data for Dzhalgin Merino were generated within this study, while data for Australian Merino, Australian Industry Merino, and Rambouillet were obtained from the SheepHapMap project. For the purposes of analysis, Australian Merino and Australian Industry Merino were combined into a single group (n = 138). To enhance the reliability of the results, three independent methods were employed to detect selection signatures: the fixation index (FST), analysis of linkage disequilibrium variation (varLD), and the cross-population number of segregating sites by length (xp-nSL). The study showed that Dzhalgin Merino have unique genetic signatures potentially associated with adaptation and productivity, which opens up new opportunities for their selection. The identified genes can become the basis for developing new breeding programs aimed at improving both the productive qualities and the adaptive abilities of the breed. Further research should be aimed at a detailed investigation of gene structure within loci under selection pressure and at clarifying the mechanisms by which these genes influence animal phenotypes. A total of 185 genes were identified within genomic regions exhibiting selection signatures. Among these, particular attention was given to EPHA6, MLLT3, ROBO1, KIAA0753, MED31, SLC13A5, and ELAVL4, which are involved in biological processes such as growth, development, and reproduction. The identified genes represent potential targets for breeding programs aimed at increasing productivity and adaptive capacity of the breed.