Cold stress in broiler: global gene expression analyses suggest a major role of CYP genes in cold responses.

To understand the exact mechanism of cold-stress in broilers depends heavily on identification of differentially expressed genes, rarely conducted so far, in the pituitary of 1 day pre- and post-cold-stress. Therefore, to identify such genes in the present study, gene expression profiling was performed using the pituitary as a model. The results showed that the expression of 15 genes were up-regulated and 15 down-regulated in the pituitary of cold stressed broilers compared with normal ones; and these differentially expressed genes belong to groups involved with catalytic activity, enzyme regulatory activity, signal transducer activity and transporter activity. Functional analysis revealed that cytochrome P450 (CYP) gene group, such as CYP7A1, CYP1A1, which are highly related to fat metabolism, involved in those biological activities. Furthermore, blood lipid levels of triglyceride, total cholesterol, low-density-lipoprotein and high-density-lipoprotein were measured, and the decreased level of blood lipid after cold stress suggested that lipid could positively affect CYP7A1 gene expression in broilers. However, future study is required to quantify the CYP gene expression during cold stress. In conclusion, our findings will not only offer basic genetic information to identify candidate genes for chicken breeding of anti-cold stress broilers, but also provide new clues for deciphering mechanisms underlining cold stress in vertebrates.