[Objective] This study aimed to investigate the methylation levels of exogenous genes and promoters and the differences of protein expression in transgenic sheep obtained by different transgenic technologies. [Method] Exogenous genes eGFP （enhanced green fluorescent protein） and FGF5 （fibroblast growth factor 5） were separately transformed into sheep by somatic cell cloning, stem cell cloning and perivitelline injection to obtain transgenic sheep, with CMV as the promoter. Bisulfite sequencing method was adopted to detect the methylation status of the promoter region and coding region of exogenous genes in tail tissues of transgenic sheep. Western blot was adopted to detect the expression level of exogenous genes. [Result] The methylation level of the promoter region with stem cell cloning was the highest, followed by somatic cell cloning, while that with perivitelline injection was the lowest; the methylation level of the eGFP coding region with perivitelline injection was the highest, followed by stem cell cloning; the methylation level of the FGF5 coding region with somatic cell cloning was higher than that with perivitelline injection. The exogenous protein expression level was negatively correlated with the methylation level of the promoter region. [Conclusion] This study indicates that different transgenic methods may influence the methylation level of exogenous genes, thus affecting exogenous gene expression.
