Effect of the Em IgH enhancer on expression of a GFP reporter gene in transfected B cells and transgenic mice Laurence Guglielmi a, Marc Le Bert b, Michel Cogne a, Yves Denizot a,* a UMR CNRS 6101, Faculte de Medecine, 2 rue Dr. Marcland, 87025 Limoges, France b CDTA, UPS CNRS 44, Orleans, France Received 19 September 2002; accepted 31 October 2002 Abstract Transgenic mice were generated to identify the first B cell maturation stage showing expression of an immunoglobulin transcriptional enhancer element (Em)-green fluorescent protein (GFP) transgene, and to check the ability of the Em element to behave as a locus control region. Flow cytometry experiments indicated that stably transfected 18/81 cells (a murine pre-B cell line) and A20 cells (a murine IgM B cell line) maintained a constant GFP expression for several months in culture. Contrasting with in vitro results, flow cytometry experiments did not highlight GFP B cells in spleen and bone marrow of Em-GFP transgenic mice and no GFP transcripts were detected by Northern blot and reverse transcriptase polymerase chain reaction analysis. In transgenic mice, the lack of GFP expression seemed related to transgene DNA methylation occurring within all organs. Our results show dramatic differences for expression of the Em-GFP transgene in vitro and in vivo. Despite that Em was reported to efficiently control the in vivo expression of other associated transgenes, it is not sufficient to sustain GFP expression in transgenic mice and to counteract developmental silencing programs that occur in the embryo.
- genomic dna
- kb afiii genomic
- transfected
- em-gfp transgenic
- kb pcr
- a20 cells
- stably transfected