Increased copy number of SOCS2 gene in Chinese gamecocks

As a member of the suppressor of cytokine signaling (SOCS) family, the SOCS2 gene has been associated with negative regulation of the inflammatory immune response and a positive effect on growth when it is overexpressed. In our previous study, using next-generation sequencing, it was found that the Luxi Game (LX, a Chinese indigenous gamecock) had an increased copy number (CN) of the SOCS2 gene. To verify the copy number increase of the SOCS2 gene in gamecocks, we quantified the copy number value in 8 chicken breeds by quantitative PCR. The results showed that the average CN values of the SOCS2 gene were highly variable among the 8 breeds, and the highest was found in LX (CN = 5.0), almost 3.5 folds as many as the lowest in Rhode Island Red (CN = 1.43). All 4 gamecock breeds possessed significantly higher CN values than others, including broilers and commercial breeds. Thus, it is suggested that most Chinese gamecocks possess an increased copy number in the SOCS2 gene, indicating the plausible functions of the SOCS2 gene in inflammation control and increased body size.