A Novel 6-bp Repeat Unit (6-bp RU) of the 13th Intron Within the Conserved EPAS1 Gene in Plateau Pika Is Capable of Altering Enhancer Activity

The plateau pika (pl-pika), a resilient mammal of the Qinghai-Tibet Plateau, exhibits remarkable adaptations to extreme conditions. This study delves into mutations within the <i>Endothelial PAS Domain Protein 1</i> (<i>EPAS1</i>) gene, crucial for high-altitude survival. Surprisingly, a novel 6-bp insertion/deletion (indel) mutation in <i>EPAS1</i>'s Intron 13, along with an additional repeat unit downstream, was discovered during PCR amplification. Genetic analysis across altitude gradients revealed a correlation between this indel's frequency and altitude, hinting at its role in altitude adaptation. Fluorescence enzyme assays unveiled enhancer activity within Intron 13, where the deletion of repeat units led to increased activity, indicating potential transcription factor binding. Notably, <i>GCM1</i> emerged as a candidate transcription factor binding to the indel site, suggesting its involvement in <i>EPAS1</i> regulation. These findings enrich our comprehension of high-altitude adaptation in plateau pikas, shedding light on the intricate interplay between genetic mutations, transcriptional regulation, and environmental pressures in evolutionary biology.