Differential Expression and Analysis of TBX3 Gene in Skin Tissues of Dun Mongolian Horses with and Without Bider Markings.
Abstract: (1) Background: The dun coat color, a wild-type phenotype in horses characterized by pigment dilution and primitive markings, is regulated by . This study explored the expression and localization of in the Bider marking (a primitive mark unique to the shoulder of horses); (2) Methods: We compared skin tissues from Bider-marked and non-Bider dun Mongolian horses. Samples were collected from the Bider area (dark-colored/light-colored shoulder), dorsal midline, and croup. Histological staining, qRT-PCR, and Western blotting were used to analyze pigment distribution and expression at mRNA and protein levels; (3) Results: Histology revealed asymmetric pigment deposition in hair shafts from light-colored areas of both Bider and non-Bider horses, whereas dark areas showed symmetric distribution. qRT-PCR and Western blotting showed expression was significantly higher in the shoulder of non-Bider horses compared to Bider horses. Conversely, Bider horses exhibited higher levels in all other sampled areas. Immunohistochemistry localized protein to the epidermis and hair follicle bulbs in both groups; (4) Conclusions: In dun Mongolian horses, expression differences between dark and light skin areas correlate with Bider markings. is implicated in this specific pigment marking, though its upstream regulation requires further study. These findings provide key insights into the mechanism behind Bider marking formation.
Publication Date: 2026-01-18 PubMed ID: 41594486PubMed Central: PMC12837385DOI: 10.3390/ani16020297Google Scholar: Lookup
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Summary
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Overview
- This study investigates the role of the TBX3 gene in the distinct Bider markings found on the skin of dun Mongolian horses, comparing areas with and without these primitive pigment patterns.
Introduction and Background
- The dun coat color in horses is a natural, wild-type phenotype characterized by a lightened pigment base and primitive markings such as dorsal stripes and leg bars.
- Bider marking is a unique primitive marking typically found on the shoulder of some dun horses, exhibiting a distinct pattern of pigmentation.
- TBX3 is a gene associated with pigmentation regulation and was hypothesized to have a role in the formation of these markings.
Research Objectives
- To analyze differential expression of the TBX3 gene at both mRNA and protein levels in dun Mongolian horses exhibiting Bider markings versus those without.
- To correlate TBX3 expression with pigment distribution and localize the protein within skin tissue structures.
Methods
- Skin tissue samples were collected from three distinct areas of the horses:
- Bider area on the shoulder, distinguished further into dark-colored and light-colored shoulder regions.
- Dorsal midline area.
- Croup area (rear part of the horse).
- Histological staining was used to examine pigment distribution in hair shafts to assess asymmetry or symmetry of pigment deposition.
- Quantitative real-time PCR (qRT-PCR) was conducted to measure TBX3 mRNA expression levels.
- Western blotting was performed to quantify TBX3 protein expression in the sampled skin tissues.
- Immunohistochemistry was employed to localize TBX3 protein within the skin layers and structures such as the epidermis and hair follicle bulbs.
Key Findings
- Histological analysis showed:
- Asymmetric pigment deposition in hair shafts from light-colored shoulder areas in both Bider-marked and non-Bider horses.
- Symmetric pigment distribution in darker-colored areas.
- Expression patterns of TBX3:
- Non-Bider horses showed significantly higher TBX3 expression in the shoulder region compared to Bider-marked horses.
- Bider markings were associated with higher TBX3 expression across other sampled skin areas (dorsal midline and croup) in Bider horses compared to their non-Bider counterparts.
- The TBX3 protein localized predominantly in:
- The epidermis, the outer skin layer.
- The bulbs of hair follicles, which are important sites for pigment-producing melanocytes and hair growth.
Interpretation and Implications
- The study suggests a direct relationship between TBX3 gene expression levels and the formation of Bider markings in dun Mongolian horses.
- The variable expression of TBX3 between dark and light skin areas aligns with the visual pigment patterns characteristic of the Bider markings.
- Localization of TBX3 in key pigment-related skin structures supports its functional role in pigment formation and regulation.
- These findings demonstrate that TBX3 is likely a critical gene contributing to the specific primitive marking phenotype; however, the upstream mechanisms that regulate TBX3 expression are still unknown and warrant further research.
Conclusions
- TBX3 plays an important role in differentiating pigment markings on the skin of dun Mongolian horses, particularly relating to the unique Bider phenotype.
- The study provides foundational insight that can help unravel the genetic and molecular basis of primitive pigmentation patterns in horses.
- Future directions include identifying the upstream regulatory factors that influence TBX3 expression and understanding how these contribute to complex coat color traits.
Cite This Article
APA
An T, Dugarjaviin M.
(2026).
Differential Expression and Analysis of TBX3 Gene in Skin Tissues of Dun Mongolian Horses with and Without Bider Markings.
Animals (Basel), 16(2), 297.
https://doi.org/10.3390/ani16020297 Publication
Researcher Affiliations
- Inner Mongolia Key Laboratory of Equine Science Research and Technology Innovation, Inner Mongolia Agricultural University, Hohhot 010018, China.
- Inner Mongolia Key Laboratory of Equine Science Research and Technology Innovation, Inner Mongolia Agricultural University, Hohhot 010018, China.
Grant Funding
- U23A20224 / National Natural Science Joint Fund Key Support Project
Conflict of Interest Statement
The authors declare no conflicts of interest.
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