SV40 intron, a potent strong intron element that effectively increases transgene expression in transfected Chinese hamster ovary cells
Key findings
The SV40 intron exhibited the highest transfection efficiency (85.3%) among five intron elements tested in Chinese hamster ovary cells, compared to IVS intron (73.8%), TPL intron (68.1%), hCMV intron A (43.2%), and CHEF1 intron (22.1%). Flow cytometry analysis showed SV40 intron-containing vectors produced the highest transient eGFP expression levels 48 hours post-transfection, significantly exceeding hCMV and CHEF1 introns (P<0.05).
In stable transfected CHO cells after 30 days of G418 selection, the SV40 intron increased eGFP protein expression 4.39-fold relative to the control IVS intron, surpassing hCMV intron (3.69-fold), TPL intron (0.18-fold), and CHEF1 intron (0.008-fold). The SV40 intron element yielded 81.8% high-level expression colonies versus 22.5% for CHEF1, demonstrating superior transgene stability and expression strength.
The SV40 intron reduced the coefficient of variation in transgene expression levels compared to other introns tested, indicating more uniform expression across stable cell populations. qRT-PCR analysis revealed that stable transgene expression levels were independent of gene copy number in CHO cells, suggesting the SV40 intron enhances expression through post-transcriptional mechanisms rather than integration efficiency.