Identification of chicken eNOS gene and differential expression in highland versus lowland chicken breeds

Nitric oxide (NO), an endothelium-derived relaxing factor, is synthesized from l-arginine by endothelial nitric oxide synthase (eNOS) in the endothelium. The objective of the present study was to preliminarily illuminate the expression of the eNOS gene in hypoxic adaptation of chicken embryonic development. The eNOS expression profiles between the Tibet and Shouguang chickens incubated under both normoxic and hypoxic conditions were detected by TaqMan real-time PCR. In this study, the chicken eNOS gene was found by both in silico cloning and RACE approaches. From the eNOS gene, we obtained a 3,310-bp mRNA sequence and a 10,666-bp DNA sequence and discovered that it was located on chicken chromosome 2 and had 7 unique transcripts. eNOS mRNA was detected in abundant amounts in some chick embryo organs (i.e., heart, liver, chorio-allantoic membrane, and lung), and expressed stably with the lowest levels in the brain. We observed that when exposed to hypoxia (13% O(2)) different embryo organ tissues had various sensitivities to hypoxia as determined by their eNOS expression profiles. Compared with the Shouguang chicken, the eNOS expression in the Tibet chicken was higher in the lung and liver, lower in the heart, and similar in the brain. In chorio-allantoic membranes, eNOS expression was higher in the Shouguang chicken than the Tibet chicken under hypoxic conditions, but not markedly different under normoxic conditions. The differences of eNOS expression between the 2 breeds may be relative to the hypoxic adaptation ability in Tibet chickens during embryonic development. This work will provide reference for future studies on the role of eNOS in hypoxic adaptation and response.