Comparative DNA methylation reveals epigenetic adaptation to high altitude in snub-nosed monkeys.

DNA methylation plays a crucial role in environmental adaptations. Here, using whole-genome bisulfite sequencing, we generated comprehensive genome-wide DNA methylation profiles for the high-altitude Yunnan snub-nosed monkey ( Rhinopithecus bieti) and the closely related golden snub-nosed monkey ( R. roxellana). Our findings indicated a slight increase in overall DNA methylation levels in golden snub-nosed monkeys compared to Yunnan snub-nosed monkeys, suggesting a higher prevalence of hypermethylated genomic regions in the former. Comparative genomic methylation analysis demonstrated that genes associated with differentially methylated regions were involved in membrane fusion, vesicular formation and trafficking, hemoglobin function, cell cycle regulation, and neuronal differentiation. These results suggest that the high-altitude-related epigenetic modifications are extensive, involving a complete adaptation process from the inhibition of single Ca ²⁺ channel proteins to multiple proteins collaboratively enhancing vesicular function or inhibiting cell differentiation and proliferation. Functional assays demonstrated that overexpression or down-regulation of candidate genes, such as SNX10, TIMELESS, and CACYBP, influenced cell viability under stress conditions. Overall, this research suggests that comparing DNA methylation across closely related species can identify novel candidate genomic regions and genes associated with local adaptations, thereby deepening our understanding of the mechanisms underlying environmental adaptations.