To investigate the relationship between the expression levels of exogenous gene and methylation level of promoter in cells derived from transgenic pigs

the EGFP fluorescence of the fifth

10

th

and 15

th

generation fibroblast of EGFP transgenic pigs were detected by flow cytometry

and the methylation status of a 560-bp region of the CMV promoter containing one CpG island including 30 CpG sites were examined by bisulfite sequencing method.  The mean fluorescence intensity declined from the fifth generation of transgenic pig cells to the 10th generation cells

however

  it increased to the level comparable to the fifth generation of cells from the 10

th

to 15

th

cells. The methylation level of the fifth

 10

th

and 15

th

generation cells of the CMV promoter were 3.64%±1.25

2.97%±1.03 and 1.65%±0.74

respectively. The difference of methylation level among different generation of transgenic cells was insignificant

which indicated that the expression level of exogenous gene EGFP was not closely correlated to the methylation level on CMV promoter.