Effect of the Emu IgH enhancer on expression of a GFP reporter gene in transfected B cells and transgenic mice.
Transgenic mice were generated to identify the first B cell maturation stage showing expression of an immunoglobulin transcriptional enhancer element (Emu)-green fluorescent protein (GFP) transgene, and to check the ability of the Emu 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 Emu-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 Emu-GFP transgene in vitro and in vivo. Despite that Emu 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.
Guglielmi
Laurence
L
UMR CNRS 6101, Faculté de Médecine, 2 rue Dr. Marcland, 87025 Limoges, France.
Le Bert
Marc
M
Cogné
Michel
M
Denizot
Yves
Y
D000818:Animals; D001402:B-Lymphocytes / Q000166:cytology* / Q000378:metabolism; D015152:Blotting, Northern; D015139:Blotting, Southern; D001853:Bone Marrow / Q000276:immunology; D002454:Cell Differentiation; D002460:Cell Line; D019175:DNA Methylation; D004742:Enhancer Elements, Genetic / Q000502:physiology*; D005260:Female; D005434:Flow Cytometry; D005786:Gene Expression Regulation; D017930:Genes, Reporter / Q000502:physiology*; D049452:Green Fluorescent Proteins; D007143:Immunoglobulin Heavy Chains / Q000235:genetics*; D008164:Luminescent Proteins / Q000096:biosynthesis* / Q000235:genetics; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D011401:Promoter Regions, Genetic; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013154:Spleen / Q000166:cytology; D014162:Transfection; D019076:Transgenes / Q000276:immunology
D007143:Immunoglobulin Heavy Chains; D008164:Luminescent Proteins; D049452:Green Fluorescent Proteins