Lung transcriptome analysis for the identification of genes involved in the hypoxic adaptation of plateau pika (Ochotona curzoniae)

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 Endothelial PAS Domain Protein 1 (EPAS1) gene, crucial for high-altitude survival. Surprisingly, a novel 6-bp insertion/deletion (indel) mutation in EPAS1'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, GCM1 emerged as a candidate transcription factor binding to the indel site, suggesting its involvement in EPAS1 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.

Comparative skin histological and transcriptomic analysis of Rana kukunoris with two different skin colors

This study compares the skin structures of Rana kukunoris with two different skin colors living in the same area of Haibei in the Northeastern Qinghai-Tibet Plateau. The skin thickness of the khaki R. kukunoris was significantly greater than that of the brown R. kukunoris (P < 0.01), and significantly more mucous and granular glands were present on the dorsal skin of the khaki frog (P < 0.05). Meanwhile, the melanocytes on the dorsal skin of the brown frog were significantly larger than those on the khaki one (P < 0.05). Morphological changes in the expansion and aggregation of melanocytes seemed to deepen the skin color of R. kukunoris. Moreover, transcriptome sequencing identified tyrosine metabolism, melanogenesis, and riboflavin metabolism as the main pathways involved in melanin formation and metabolism in brown R. kukunoris. TYR, MC1R was upregulated as the skin color of R. kukunoris was deepened and contributed to melanin production and metabolism. In contrast, the khaki frog had significantly more upregulated genes and metabolic pathways related to autoimmunity. The khaki frog appeared to defend against ultraviolet (UV) radiation-induced damage by secreting mucus and small molecular peptides, whereas the brown frog protected itself by distributing a large amount of melanin. Hence, the different skin colors of R. kukunoris might represent different adaptation strategies for survival in the intense UV radiation environment of the Qinghai-Tibet Plateau.

Transcriptome analysis of pika heart tissue reveals mechanisms underlying the adaptation of a keystone species on the roof of the world

High-altitude environments impose intense stresses on living organisms and drive striking phenotypic and genetic adaptations, such as hypoxia resistance, cold tolerance, and increases in metabolic capacity and body mass. As one of the most successful and dominant mammals on the Qinghai-Tibetan Plateau (QHTP), the plateau pika (Ochotona curzoniae) has adapted to the extreme environments of the highest altitudes of this region and exhibits tolerance to cold and hypoxia, in contrast to closely related species that inhabit the peripheral alpine bush or forests. To explore the potential genetic mechanisms underlying the adaptation of O. curzoniae to a high-altitude environment, we sequenced the heart tissue transcriptomes of adult plateau pikas (comparing specimens from sites at two different altitudes) and Gansu pikas (O. cansus). Differential expression analysis and weighted gene co-expression network analysis (WGCNA) were used to identify differentially expressed genes (DEGs) and their primary functions. Key genes and pathways related to high-altitude adaptation were identified. In addition to the biological processes of signal transduction, energy metabolism and material transport, the identified plateau pika genes were mainly enriched in biological pathways such as the negative regulation of smooth muscle cell proliferation, the apoptosis signalling pathway, the cellular response to DNA damage stimulus, and ossification involved in bone maturation and heart development. Our results showed that the plateau pika has adapted to the extreme environments of the QHTP via protection against cardiomyopathy, tissue structure alterations and improvements in the blood circulation system and energy metabolism. These adaptations shed light on how pikas thrive on the roof of the world.