RNA Modification Profiles and m6A Regulatory Patterns in the Lungs of Sheep at Different Altitudes

The lung is a key organ for oxygen uptake and gas exchange and plays an important role in adaptation to hypoxic environments at high altitudes. RNA modifications represent an important layer of epitranscriptomic regulation and participate in cellular processes by affecting RNA stability, splicing, translation, and degradation. In this study, the right lung parenchyma from low-altitude Hu sheep (LL), mid-altitude Tibetan sheep (ML), and high-altitude Tibetan sheep (HL) were used to investigate altitude-associated RNA modification profiles and m6A regulatory patterns. A UPLC-MS/MS platform was employed to quantitatively detect 55 RNA modifications, while RT-qPCR and Western blot analyses were performed to evaluate the expression of HIF1α, HIF2α, and m6A-related regulatory factors. The results showed distinct differences in lung RNA modification profiles among the three groups. Compared with the LL and ML groups, the HL group exhibited reduced m6A and m6Am levels, whereas several non- m6A modifications, including t6A, m1G, m2G, m7G, m3C, and m5C, showed increasing trends. The expression levels of HIF1α and HIF2α were higher in the ML and HL groups than in the LL group. In addition, METTL3, METTL14, WTAP, and several YTH family reader proteins were downregulated in the HL group at both the protein and mRNA levels. These findings indicate that sheep lung RNA modification profiles and the m6A regulatory machinery differ among groups with different altitude-related adaptation backgrounds. Collectively, these findings reveal epitranscriptomic differences associated with altitude and breed in sheep lungs and provide a basis for further investigation of the role of m6A regulation in high-altitude adaptation.