Download Yak genome provides new insights into high altitude adaptation

EYE
ON
CHINA
Yak genome provides new insights into high altitude adaptation
A
n international team, led by Lanzhou
University, comprising BGI, the
world’s largest genomics organization, Institute of Kunming Zoology, Chinese
Academy of Sciences as well as the other
12 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
recently published online in Nature Genetics.
Scienceshot made a timely comment on yak
genome themed “What gets yak high”.
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 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
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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 2,657Mb draft
yak genome assembly that had 65-fold
coverage. They 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 the comparative genomic
analyses between yak and cattle, a closely
related animal that typically lives at much
lower altitudes. Although the yak and cattle
were estimated to have diverged around
4.9 million years ago, many of the yak and
cattle genes have remained very similar, with
the two animals sharing 45 percent protein
identity and 99.5 percent protein similarity.
However, they identified distinct gene
expansions related to sensory perception and
energy metabolism-related in yak.
In addition, researchers also found
an enrichment of protein domains related
to the extracellular environment and
hypoxic stress. Especially, they found the
orthologous genes in yak related to hypoxia
and nutrition metabolism had undergone
positively selected and rapid evolution. For
example, they found three genes that may
play important roles in regulating body’s
response to hypoxia, or oxygen deprivation,
at high-altitudes, and five genes that were
related with the optimization of the energy
from the poor foods in the extreme plateau.
Researchers referred that the study
on high-altitude adaptation may help to
improve current understanding, treatment,
and prevention of altitude sickness and
other hypoxia-related diseases in humans.
Moreover, the yak genome provided a
valuable resource for accelerating the
genetic improvement of milk and meat
production of this important animal.