Transcriptional activities of human elongation factor-1 alpha and cytomegalovirus promoter in transgenic dogs generated by somatic cell nuclear transfer

Abstract

Recent advances in somatic cell nuclear transfer (SCNT) in canines facilitate the production of canine transgenic models. Owing to the importance of stable and strong promoter activity in transgenic animals, we tested human elongation factor 1 alpha (hEF1 alpha) and cytomegalovirus (CMV) promoter sequences in SCNT transgenic dogs. After transfection, transgenic donor fibroblasts with the hEF1 alpha-enhanced green fluorescence protein (EGFP) transgene were successfully isolated using fluorescence-activated cell sorting (FACS). We obtained four puppies, after SCNT, and identified three puppies as being transgenic using PCR analysis. Unexpectedly, EGFP regulated by hEF1 alpha promoter was not observed at the organismal and cellular levels in these transgenic dogs. EGFP expression was rescued by the inhibition of DNA methyltransferases, implying that the hEF1 alpha promoter is silenced by DNA methylation. Next, donor cells with CMV-EGFP transgene were successfully established and SCNT was performed. Three puppies of six born puppies were confirmed to be transgenic. Unlike hEF1 alpha-regulated EGFP, CMV-regulated EGFP was strongly detectable at both the organismal and cellular levels in all transgenic dogs, even after 19 months. In conclusion, our study suggests that the CMV promoter is more suitable, than the hEF1 alpha promoter, for stable transgene expression in SCNT-derived transgenic canine model.