Yaks are on the way. (Photo from Unsplash)
For the folks who suffer severe altitude sickness when traveling to the Qinghai-Tibetan Plateau or other high-altitude sites, the wild yaks, capable of keeping running and running on these wild lands, would be a top envy target. You may be awed by the prime beauty of these herd animals caught at first sight, or you may struggle to catch your breath when swearing feebly – What the heck! How these beasts do that!
A newly reported study from Nature Communications reveals some unique endothelial cells in yak lungs, which are not to be seen in domestic cattle. These cells were found to help forge elastic lungs for the yaks.
It is known that the yak’s blood, lung, and heart systems have been evolved to meet the challenge at high altitudes. They can better withstand hypoxia because they have higher hemoglobin content and red blood cell count. They have bigger lungs and hearts than those of age-matched domestic cattle. They also have more abundant blood vessels in the lung tissue. Yet, what exact genomic changes enable their high-altitude adaption remains to be explored.
Next-generation sequencing has proven to be a powerful tool for studying genomic changes. However, the limitation of the genome assembly using short reads makes it impossible to accurately detect the genomic changes that come at a big scale, such as deletions, insertions, duplications, and inversions.
Using the Nanopore technique for long reads and the Hi-C technology for genome assembly, the team successfully get two long-read genome assemblies of wild and domestic yak.
By comparing these long-read genomes with a high-quality reference genome of domestic cattle, researchers found that many genomic changes lie in the noncoding sequences, including promoter and untranslated regions (UTR), which usually regulate the expression of nearby genes. They suggested that the yaks may benefit from the genomic changes in the promoters of hypoxia-related genes.
They also identified a yak-specific endothelial cell subtype using single-cell transcriptome sequencing, a technique widely used for grouping cells with similar mRNA expression profiles. These unique cells can enhance the medial thickness of micro-vessels and the formation of elastic fibers in yak lungs.
Researchers believe that their findings would have important implications for understanding the physiological and pathological responses of large mammals and humans to hypoxia.
“These high-quality genomes and single-cell RNA-seq data serve an important source for future research on bovine species,” say the researchers.
(By YAN Fusheng)
Gao, X., Wang, S., Wang, Y. F., et al. (2022). Long read genome assemblies complemented by single cell RNA-sequencing reveal genetic and cellular mechanisms underlying the adaptive evolution of yak. Nat Commun, 13(1), 4887. doi:10.1038/s41467-022-32164-9