Résumé
To ensure the B cell differentiation stage specificity of the intronic Eμ element and of the locus control region (LCR) that lies downstream of the IgH chain locus, we generated transgenic mice harboring a V
H promoter-GFP reporter gene linked to the 3′LCR region and the Eμ element. By flow cytometry, GFP
+ lymphocytes were observed amongst pro-B cells (B220
+CD43
+CD117
+) and at all stages of differentiation up to mature B cells (B220
+IgM
+IgD
+). Expression was strictly confined to cells committed to the B lymphocyte lineage as judged by the lack of GFP
+Thy1,2
+ cells (T lymphocytes) and GFP
+B220
−CD117
+CD43
+ cells (uncommitted lymphohematopoietic progenitors). Therefore, the Eμ-GFP-3′LCR transgene is not expressed by hematopoietic stem cells, begins its expression in pro-B cells and is specifically active at all stages of B cell maturation. The combination of 3′ and 5′ IgH regulatory elements thus appears as a potentially useful cassette in transgenes that require a stringent and early B lineage-specific expression.