Analysis of circRNA Differential Expression and ceRNA Network Construction in Yak Mammary Glands Across Different Physiological Stages

Yak is a distinctive domestic animal adapted to the Qinghai–Tibet Plateau, and its lactation performance is restricted by extreme high-altitude conditions. Despite the growing recognition of circRNAs as important regulators of mammary gland development in other species, no study has yet systematically investigated the stage-specific circRNA expression landscapes in yak mammary glands across gestation, lactation, and non-pregnant periods, or the potential ceRNA networks through which these circRNA may participate in regulating milk synthesis and mammary cell proliferation under high-altitude conditions. This study aimed to characterize circRNA expression features and lactation regulation in yak mammary glands at the gestation, lactation, and non-pregnant stages. Total RNA sequencing was performed on mammary specimens, followed by differential screening, functional enrichment, ceRNA network construction, and qPCR verification. Numerous stage-biased circRNAs were identified, among which circNFATC2, circTRPS1 and circTAF3 were highlighted as hub candidates potentially involved in mammary cell differentiation, milk synthesis, and energy metabolism, with qPCR validating sequencing outcomes. Our results provide a comprehensive circRNA expression atlas and candidate molecular markers for understanding lactation regulation in high-altitude yaks, offering a valuable foundation for the future genetic improvement of milk production traits.