Tissue-Specific Expression and Functional Role of Keratin 1 (KRT1) in Sheep Horn Development

Qiao Mei^1,2Hao Li^2,3Guoqing Zhang^2,3Zhu Meng^2,3Shiwen Zhang^2,3Fei Liu^2,3Zhangyuan Pan^2,3*Jie Yang^1*

• ¹Xinjiang University College of Life Science and Technology, Urumqi, China
• ²State Key Laboratory of Animal Biotech Breeding, Institute of Animal Science, Chinese Academy of Agricultural Sciences, Beijing, China
• ³Hainan University Sanya Nanfan Research Institute, Sanya, China

Systematic analysis of the key horn morphogenesis gene KRT1 revealed the molecular mechanism underlying sheep horn type differentiation and its value for breeding applications. Sheep horn type differentiation significantly impacts farming economics and animal welfare. This study is the first to systematically elucidate the central role of the keratin gene KRT1 in regulating sheep horn type differentiation. Through integrated multi-omics analysis, we uncovered the expression patterns, key functional loci, and molecular interaction mechanisms of the KRT1 gene, The KRT1 gene exhibits specific high expression in horn tissue, periosteum, and skin, while it is nearly absent in non-keratinized tissues such as internal organs; cross-species comparisons (sheep, cattle, human, pig) confirmed its ubiquitous high expression in skin and horn. Sequence and structural analysis identified 11 conserved amino acid loci specific to horned artiodactyls. Among these, the K312 loci located in the α-helical domain is critical. It maintains keratin network stability by forming a hydrogen bond (strength 2.9) with E262 of KRT10; p.K312T&S mutation at loci in hornless animals disrupts the interaction. Integrating RNA-seq data, we screened 4 allele-specific expression (ASE) loci (with significant enrichment of the ref allele in the scurred group and complete absence of the alt allele in the SHE group); integrating whole-genome sequencing (WGS) data, we identified 32 functional SNPs. Among these, the homozygous wild-type genotypes at 4 SNP loci showed a significant positive correlation with horn length (p < 0.05), while heterozygous genotypes resulted in shortened horn length. Linkage disequilibrium analysis identified 9 haplotype blocks containing 13 highly differentiated SNPs (Fst >0.05), constituting core genetic units associated with horn type. This study systematically deciphers the molecular pathway by which the KRT1 gene influences horn morphological development through regulating the keratin interaction network, providing crucial evidence for understanding the molecular mechanism of sheep horn development and laying a solid theoretical foundation for molecular marker-assisted selection.