An international team, led by Lanzhou University, and including BGI, the world's largest genomics organization, the Institute of Kunming Zoology, the Chinese Academy of Sciences, as well as twelve other institutes, has completed the genomic sequence and analyses of a female domestic yak, which provides important insights into understanding mammalian divergence and adaptation at high altitude. This study was published online on July 1, 2012 in Nature Genetics. As an iconic symbol of Tibet and of high altitude, the yak (Bos grunniens) is the most important domesticated species for Tibetans living at high altitude in China's Qinghai Province, which could provide meat and other basic resources, such as milk, transportation, dried dung for fuel, and hides for tented accommodation. Yaks have many anatomical and physiological traits that enable them to live at high altitude, including high metabolism, acute senses, impressive foraging ability, enlarged hearts and lungs, and a lack of blood vessel constriction in the lungs when faced with relatively low oxygen conditions. In the study, researchers sequenced the genome of a female domestic yak using high-throughput sequencing technology. The genomic data yielded a 2,657-Mb draft yak genome assembly that had 65-fold coverage. The researchers also conducted transcriptome sequencing on RNA samples derived from fresh heart, liver, brain, stomach, and lung tissues collected from the same yak. Based on the transcriptome data, researchers estimated that the yak genome contains 22,282 protein-coding genes and 2.2 million heterozygous SNPs. In order to understand evolutionary adaptation of yak to the high altitude, the team conducted comparative genomic analyses between yak and cattle, a closely related animal that typically lives at much lower altitudes.
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