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Comparative genomic analysis of oxytocin and oxytocin receptor genes in the family Equidae.
Abstract: The oxytocin (OXT) - oxytocin receptor (OXTR) system regulates diverse biological processes including social behavior, stress responses, and processes related to domestication. While OXT is highly conserved, OXTR shows greater variability, which may contribute to species-specific adaptations. Methods: Comparative genomic analyses of OXT and OXTR coding sequences were performed across equid species using available genome assemblies and newly generated sequences obtained by next-generation sequencing. Phylogenetic relationships were inferred using maximum likelihood methods. Selection was assessed using codon-based approaches (FEL, SLAC, FUBAR). The potential effects of amino acid substitutions were predicted using in silico tools, including SIFT, Missense3D, and NetPhos. Results: The OXT gene was conserved across equids, with no variation in the amino acid sequence. The OXTR gene was more variable, with most nonsynonymous substitutions located in the C-terminal region. Predominantly purifying selection was detected, with limited diversifying selection. OXTR gene variability differed among species, being lower in horses and higher in zebras and wild asses. Differences between domesticated and nondomesticated groups were observed. Trans-species haplotype sharing and distinct patterns at amino acid positions 182 and 344 were identified. Conclusions: The OXTR gene shows genetic variability in equids, with differences between domesticated and nondomesticated species. Some variants may represent candidate markers for future studies of domestication, behavior, and comparisons between ancient and modern DNA.
© 2026. The Author(s), under exclusive licence to Springer Nature B.V.
Publication Date: 2026-08-14 PubMed ID: 42599569PubMed Central: 12229615DOI: 10.1007/s11033-026-12585-1Google Scholar: Lookup The Equine Research Bank provides access to a large database of publicly available scientific literature. Inclusion in the Research Bank does not imply endorsement of study methods or findings by Mad Barn.
- Journal Article
- Comparative Study
Summary
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Comparative genomic analysis of oxytocin and oxytocin receptor genes in equids reveals that while the oxytocin gene is highly conserved, the oxytocin receptor gene exhibits genetic variability, particularly differing between domesticated and nondomesticated species.
Background and Purpose
- The oxytocin (OXT) and oxytocin receptor (OXTR) system plays crucial roles in regulating social behaviors, stress response, and traits linked to domestication in animals.
- Although the OXT gene is generally conserved across species, the OXTR gene shows more variability, potentially underpinning species-specific adaptations among equids (horses, zebras, wild asses).
- The study aimed to investigate the genetic diversity and evolutionary pressures on OXT and OXTR genes across different equid species using genomic data.
Methods
- Comparative genomic analyses were conducted on the coding sequences of the OXT and OXTR genes using publicly available equid genome assemblies and newly sequenced data from next-generation sequencing efforts.
- Phylogenetic relationships among species were inferred using maximum likelihood methods to understand evolutionary linkages.
- Selection pressures on genes were evaluated through codon-based models, employing methods such as FEL (Fixed Effects Likelihood), SLAC (Single-Likelihood Ancestor Counting), and FUBAR (Fast Unconstrained Bayesian AppRoximation).
- Computational predictive tools (SIFT, Missense3D, NetPhos) were used to assess the potential functional impact of amino acid substitutions identified in OXTR sequences.
Key Findings
- OXT Gene Conservation: The oxytocin gene showed no amino acid sequence variation across all equid species analyzed, demonstrating high conservation.
- OXTR Gene Variability: The oxytocin receptor gene exhibited genetic variability, mainly in the C-terminal region of the encoded protein, where most nonsynonymous (amino acid-changing) substitutions were found.
- Selection Patterns: The OXTR gene was predominantly under purifying selection, indicating evolutionary pressure to maintain its function, but some limited diversifying selection (positive selection at certain sites) was detected.
- Species Differences:
- Domesticated horses showed lower genetic variability in OXTR compared to nondomesticated species like zebras and wild asses, which displayed higher variability.
- Distinct differences were noted between domesticated and nondomesticated groups in the patterns of OXTR gene variation.
- Haplotype Sharing and Key Amino Acid Sites:
- Some haplotypes (specific combinations of genetic variants) were shared trans-species, indicating possible conserved or ancestral variants.
- Notable variations at amino acid positions 182 and 344 were identified, possibly linked to functional differences.
Conclusions and Implications
- The strong conservation of the OXT gene across equids confirms its critical and stable biological role.
- The observed variability in the OXTR gene, especially marked between domesticated and nondomesticated species, suggests that OXTR variants might have contributed to adaptations related to domestication and behavior.
- Specific OXTR variants identified in this study could serve as candidate genetic markers for future research focused on domestication processes, social behavior traits, and evolutionary comparisons using ancient and modern DNA samples.
- This study enhances our understanding of how genetic variation in neuropeptide receptor genes might influence species-specific traits in the Equidae family.
Cite This Article
APA
Vychodilova L, Janova E, Plasil M, Futas J, Stejskalova K, Oppelt J, Horin P.
(2026).
Comparative genomic analysis of oxytocin and oxytocin receptor genes in the family Equidae.
Mol Biol Rep, 53(1), 1405.
https://doi.org/10.1007/s11033-026-12585-1 Publication
Researcher Affiliations
- Department of Animal Genetics, Faculty of Veterinary Medicine, University of Veterinary Sciences Brno, Brno, 61242, Czech Republic. vychodiloval@vfu.cz.
- Department of Animal Genetics, Faculty of Veterinary Medicine, University of Veterinary Sciences Brno, Brno, 61242, Czech Republic.
- RG Animal Immunogenomics, CEITEC VETUNI, University of Veterinary Sciences Brno, Brno, Czech Republic.
- Department of Animal Genetics, Faculty of Veterinary Medicine, University of Veterinary Sciences Brno, Brno, 61242, Czech Republic.
- RG Animal Immunogenomics, CEITEC VETUNI, University of Veterinary Sciences Brno, Brno, Czech Republic.
- Department of Animal Genetics, Faculty of Veterinary Medicine, University of Veterinary Sciences Brno, Brno, 61242, Czech Republic.
- RG Animal Immunogenomics, CEITEC VETUNI, University of Veterinary Sciences Brno, Brno, Czech Republic.
- Department of Animal Genetics, Faculty of Veterinary Medicine, University of Veterinary Sciences Brno, Brno, 61242, Czech Republic.
- RG Animal Immunogenomics, CEITEC VETUNI, University of Veterinary Sciences Brno, Brno, Czech Republic.
MeSH Terms
- Animals
- Receptors, Oxytocin / genetics
- Oxytocin / genetics
- Phylogeny
- Equidae / genetics
- Genomics / methods
- Genetic Variation
- Amino Acid Sequence
- Evolution, Molecular
- Horses / genetics
- Haplotypes
- Selection, Genetic
Grant Funding
- 2024ITA32 / ITA VETUNI BRNO
Conflict of Interest Statement
Declarations. Competing interests: The authors declare no competing interests. Consent for publication: Not applicable. Ethics approval and consent to participate: All blood samples used in this study were archived samples originally collected for the purposes of other projects [13, 23]. All these samples were collected by licensed veterinarians in agreement with all ethical, welfare and professional standards. Generative AI-assisted technologies in the writing process: The authors used ChatGPT (OpenAI) for language editing and take full responsibility for the content.
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