Blimp-1 gene regulatory region directs EGFP expression in multiple hematopoietic lineages and testis in mice

The B lymphocyte-induced maturation protein-1 (Blimp-1) is a transcriptional repressor involved in B cell terminal differentiation. Recent studies suggest that it also plays roles in the differentiation of myeloid and T cells. Using reporter gene analysis, we found that the mouse Blimp-1 promoter constructs of 4.4 kb, 2.5 kb and 1.6 kb exerted similar transcription activity in vitro. To study the Blimp-1 promoter function in vivo, we generated a mouse transgenic line in which the expression of EGFP is driven by the 4.4 kb Blimp-1 promoter fragment. EGFP expression was detected in multiple hematopoietic lineages including hematopoietic progenitor cells (c-kit+), B cells at various developmental stages (B220+, IgM+, IgD+ and CD138+), myeloid cells (Gr1+ and CD11b+) and T cells (CD4+ and CD8+). Furthermore, we demonstrated, for the first time, that this Blimp-1 promoter fragment also drives EGFP expression in erythroid lineage (Ter119+) and embryonic livers. Finally, EGFP was expressed in the testes of transgenic mice in a cell-specific manner with expression weakly in primary spermatocytes and strongly in spermatids, but not in spermatogonia or spermatozoa. Our studies collectively suggest that Blimp-1 may play a general role in the development of hematopoietic lineages and a stage-specific role in spermatogenesis.