Coat Color-Associated Transcriptomic Differences of Black and White Hortobágyi Racka Sheep Using the RNA-Seq Technique.

Coat color is an important visible phenotype in sheep and may reflect underlying differences in pigmentation-related molecular regulation. However, the transcriptomic mechanisms underlying black and white coat-color divergence in Hortobágyi Racka sheep remain insufficiently characterized. To address this, this study employed high-throughput RNA sequencing to analyze the skin transcriptome profiles of black- and white-coated Hortobágyi Racka sheep and identified functional pathways associated with coat-color difference. We identified 108 DEGs; 25 downregulated and 83 upregulated (FC > 1.5, p < 0.05) in black-coated sheep compared with white-coated sheep, with the most significant genes including TYRP1, PMEL, TRPM1, MLANA, SLC24A4, SLC45A2, DCT, OCA2, and DDC (p adj < 0.05). Overall, the GO, KEGG, and PPI analyses consistently indicated that coat-color divergence in Hortobágyi Racka sheep was primarily associated with melanogenesis, melanosome biology, and tyrosine metabolism, while also suggesting possible links with broader cellular process related to redox balance, energy metabolism, and stress responses. However, these broader adaptive interpretations should be considered hypothesis-generating and require further validation using larger cohorts, phenotypic measurements, and functional assays. Our study provides a transcriptomic framework connecting coat-color phenotypes to pigmentation regulatory networks and provides a foundation for investigating the possible adaptive significance of coat-color variation in sheep.