Oxygen is one of the critical determinants for normal embryonic and fetal development. In avian embryos, lack of oxygen will lead to high fetal mortality, heteroplasia, and cardiovascular dysfunction. Tibetan chicken is a breed native to Tibet that could survive and keep higher hatchability regardless of negative effects of hypoxia. Generally, adaptive animals in high altitudes are characterized by higher hemoglobin concentrations and oxygen affinity. In the present study, the capacity of oxygen supply in late chick embryo (including d 17, 19, and 21) was compared between Tibetan chicken and a lowland breed, Dwarf White chicken, by determining the hemoglobin concentrations and oxygen equilibrium curves in both hypoxic (13% O(2)) and normoxic (21% O(2)) conditions. The results showed that a higher level of hemoglobin concentration was induced by hypoxia in Tibetan chicken embryos, and the hemoglobin could perform with better cooperativity and deliver oxygen to tissues more easily. Further investigation revealed that the carbonic anhydrase II mRNA in red blood cells of Tibetan chicken was increasingly induced to a higher level in hypoxia than that of the lowland breed. These results suggested that the stronger capacity of oxygen dissociation was an important characteristic of Tibetan chicken embryo to survive in hypoxia and the upregulating mode of carbonic anhydrase II mRNA might assist this dissociation. Therefore, for avian at high altitudes, the efficient dissociation of oxygen might reveal another aspect associated with the hypoxia adaptability.

As a newly described member of the apolipoprotein gene family, apolipoprotein A5 (APOA5) has been suggested to play a key role in the triglyceride metabolism in both human and mice. The aim of this study was to identify the porcine (Sus scrofa) APOA5 gene, determine its mRNA and its mutations that are associated with lipid accumulation. The porcine APOA5 cDNA was amplified by reverse transcriptase polymerase chain reaction using the information of the mouse or other mammals. It had been determined that the open reading frame of the porcine APOA5 gene consists of 1092 bp, which encodes a predicted protein composed of 363 amino acids with a similarity to bovine (80.43%) and to human (78.47%). The expression analysis indicated that the porcine APOA5 gene was expressed in hypophysis, fat and liver. Twelve single nucleotide polymorphisms (SNPs), including 4 SNPs in the 5 0 end, 1 SNP in second intron, 1 SNP in third exon and 6 SNPs in the 3 0 end, were identified in the porcine APOA5 gene and genotyped on the Jinhua 3 Pietrain F 2 reference population, it had revealed that the SNP of C1834T was significantly associated with average backfat thickness and leaf fat weight ( P , 0.01 and P , 0.05, respectively). In conclusion, this study has got basic information of the porcine APOA5 gene and provides evidence that the APOA5 gene could be a potential candidate gene for fat deposition.