Study on Tibetan Chicken embryonic adaptability to chronic hypoxia by revealing differential gene expression in heart tissue

Abstract

Oxygen concentration is essential for appropriate metabolism. Hypoxia can exert a significant impact on physiological alteration of the cell and organism. Tibetan Chicken (Gallus gallus) is a Chinese indigenous breed inhabiting in Tibetan areas, which is also a chicken breed living at high altitude for the longest time in the world. It has developed an adaptive mechanism to hypoxia, which is demonstrated by that Tibetan Chicken has much higher hatchability than low-land chicken breeds in high-altitude areas of Tibet. In the present study, Tibetan Chicken fertilized full sib eggs were incubated up to Hamburger-Hamilton stage 43 under 13% and 21% oxygen concentration, respectively. Shouguang Chicken and Dwarf Recessive White Chicken were used as control groups. The hearts in all of the 3 chicken breeds under hypoxic and normoxic conditions were isolated and hybridized to GeneChip(R) Chicken Genome Array to study molecular mechanisms underlying the adaptation to high altitude of Tibetan Chicken. As a result, 50 transcripts highly expressed in hypoxia are screened out. Among up-regulated genes, some are involved in the gene ontology (GO) such as cell growth, cell difference, muscle contraction and signal transduction. However, the expression levels of 21 transcripts are lower in hypoxia than those in normoxia. Some down-regulated genes take part in cell communication, ion transport, protein amino acid phosphorylation and signal transduction. Interestingly, gene enrichment analyses of these differential gene expressions are mainly associated with immune system response and ion channel activity in response to stimulus. Moreover, the transcriptional expression profiles analyzed by hierarchical clustering and CPP-SOM software in all of the 3 different chicken breeds revealed that Tibetan Chicken is much closely related to Shouguang Chicken rather than Dwarf Recessive White Chicken. In addition, 12 transcripts of Tibetan Chicken breed-specific expressed genes were identified, which seem to result in a more effective and efficient induction of energy demand and signal transduction of transcription and suppression of abnormal development in response to hypoxia. These findings will be beneficial in clarifying the adaptive molecular mechanism of Tibetan Chicken as well as providing new insight into cardiovascular disease at high altitude medicine.

Mitochondrial physiology in the skeletal and cardiac muscles is altered in torrent ducks, Merganetta armata, from high altitudes in the Andes

“…The heightened activity of CK in the heart of highland torrent ducks might be important for facilitating energy supply. The greater CK activity in highland versus lowland torrent ducks is consistent with previous observations in Tibetan chickens, in which developmental hypoxia increased expression of mitochondrial CK in the heart (Li and Zhao, 2009). This response to hypoxia in ovo seemed to be unique to this highland strain of chicken, because lowland-strain chickens did not increase mitochondrial CK expression in the heart in response to the same developmental hypoxia exposure (Li and Zhao, 2009).…”

“…The greater CK activity in highland versus lowland torrent ducks is consistent with previous observations in Tibetan chickens, in which developmental hypoxia increased expression of mitochondrial CK in the heart (Li and Zhao, 2009). This response to hypoxia in ovo seemed to be unique to this highland strain of chicken, because lowland-strain chickens did not increase mitochondrial CK expression in the heart in response to the same developmental hypoxia exposure (Li and Zhao, 2009). Expression of mitochondrial CK is also elevated in the locomotory muscle of high-altitude deer mice compared to their low-altitude counterparts (Scott et al, 2015a,b).…”

Elevated performance: the unique physiology of birds that fly at high altitudes

“…and W. K. Milsom, unpublished). Cardiac specializations in high-altitude birds may have a transcriptional basis, based on a comparison of cardiac gene expression in late-stage embryos of Tibetan chickens and lowland breeds (Li and Zhao, 2009): embryonic hypoxia altered the expression of over 70 transcripts in all chickens, but an additional 12 genes (involved in energy metabolism, signal transduction, transcriptional regulation, cell proliferation, contraction and protein folding) were differentially expressed in only the highland Tibetan breed. Overall, these findings lend some credence to a previous suggestion that the hypoxaemia tolerance of the heart has a strong influence on the ability to fly at high altitudes (Scheid, 1990).…”

“…Increases in aerobic capacity, and the associated increases in overall mitochondrial abundance, could be important for counterbalancing the inhibitory effects of low O 2 levels on the respiration of individual mitochondria [this strategy is discussed in Hochachka (Hochachka, 1985)]. Mitochondrial ATP production is also more strongly regulated by creatine kinase in bar-headed geese than in low-altitude waterfowl (Scott et al, 2009a) and the expression of mitochondrial creatine kinase is upregulated by hypoxia in Tibetan chickens (Li and Zhao, 2009). A potential consequence of these alterations is that energy supply and demand in the muscle is better coupled via the creatine kinase shuttle, a system important for moving ATP equivalents around the cell [this system is described in Andrienko et al (Andrienko et al, 2003)].…”

Latest notable achievements in genomics

“…The study on Tibetan chicken's embryonic adaptability to chronic hypoxia showed that Tibetan chickens have much higher hatch-ability than low-land chicken breeds in high-altitude areas of Tibet [28]. Most Sox genes directly affect cell fate determination and differentiation.…”