Identification of cis-regulatory elements provides insights into tissue-specific gene regulation in the sheep genome

Annotation of regulatory elements is essential for understanding mechanisms underlying gene regulation, particularly tissue-specific regulation in human and animals. Here, we characterize 274,682 enhancers and 25,975 promoters across 24 tissues from an adult female sheep using ChIP-seq, ATAC-seq, CAGE-seq, RRBS, WGBS, and RNA-seq. We identify seven neural development-related genes with over 10 enhancers in brain tissues, highlighting the role of tissue-specific regulation. Cis-regulatory enhancer-promoter combinations provide insights into tissue-specific enhancers, such as the cerebellum-specific enhancer (chr15: 57390520-57390685) regulating BDNF, which is expressed in both the cerebellum and cerebral cortex. Comparative analysis of enhancer-promoter combinations in human, mouse, pig, cattle, and sheep reveals ruminant-specific pathways, including pentose catabolism and long-chain fatty acid import regulation. A milk fat yield quantitative trait locus (QTL) identified within an enhancer interacts with the fat metabolism-related gene COMMD1, and a birth weight-associated QTL detected within a cerebellum-specific enhancer regulates XKR4. This study provides a robust framework for exploring cis-regulatory mechanisms and tissue-specific regulation, advancing the functional annotation of the sheep reference genome.