Comparative transcriptomic and proteomic analyses provide insights into functional genes for hypoxic adaptation in embryos of Tibetan chickens

Tibetan chickens, a unique plateau breed, have good performances to adapt to high-altitude hypoxic environments. A number of positively selected genes have been reported in Tibetan chickens; however, the mechanisms of gene expression for hypoxia adaptation are not fully understood. In the present study, eggs from Tibetan (TC) and Chahua (CH) chickens were incubated under hypoxic and normoxic conditions, and vascularization in the chorioallantoic membrane (CAM) of embryos was observed. We found that the vessel density index (VDI) in CAM of TCs was lower than in CHs under hypoxia incubation.Proteomic analyses of CAM tissues were performed in TC and CH embryos under hypoxic incubation using iTRAQ. We obtained 387 differentially expressed proteins (DEPs) that were mainly enriched in angiogenesis, vasculature development, blood vessel morphogenesis, blood circulation, renin-angiotensin system, and HIF-1 and VEGF signaling pathways. Twenty-six genes involved in angiogenesis and blood circulation, two genes involved in ion transport, and six genes that regulated energy metabolism were identified as candidate functional genes in regulating hypoxic adaption of chicken embryos. Therefore, this research provided insights into the molecular mechanism of hypoxia adaptation in Tibetan chickens.