Expression profiling, functional characterization, and potential functional variants of the COL7A1 gene in sheep horn development

The morphological diversity of sheep horns affects livestock production, yet its molecular regulation is poorly understood. COL7A1, essential for anchoring the epidermis to the dermis, was investigated using RNA-seq, WGS, and protein interaction prediction. COL7A1 was highly expressed in soft horn and skin, with higher levels in Scurred than Horned sheep (p < 0.05), suggesting a role in horn morphology. Cross-species alignment of 18 COL7A1 sequences revealed 15 amino acids unique to horned ruminants. RNA-seq and WGS identified four allele-specific expression (ASE) loci and 18 SNPs linked to horn traits. Two missense variants-SNP8 (p.Glu181Asp) and SNP14 (p.Ala2857Thr)-may alter protein structure, with SNP14 showing ASE. Kompetitive Allele-Specific PCR (KASP) genotyping of SNP4 and SNP8 confirmed associations with horn length (p < 0.05). Protein interaction modeling indicated COL7A1 synergizes with laminin γ2 (LAMC2), implicating basement membrane assembly. These results provided molecular insights into ovine horn development and support marker-assisted selection.