PRDM1/Blimp-1 is expressed in human B-lymphocytes committed to the plasma cell lineage.

PRDM1/Blimp-1 (in human and mouse, respectively) has a central role in determining and shaping the secretory arm of mature B-cell differentiation. In this study, a mouse monoclonal antibody that recognizes PRDM1 was used to detail its distribution in normal human lymphoid tissue and in lymphoid neoplasms that correspond to different stages of B-cell differentiation. PRDM1 was expressed in germinal centre blasts that co-express Pax5, CD19, CD20, and CD10, but not BCL6 or MTA-3.

Thyroid hormone T3 acting through the thyroid hormone alpha receptor is necessary for implementation of erythropoiesis in the neonatal spleen environment in the mouse.

Thyroid hormones (THs) mediate many physiological and developmental functions in vertebrates. All these functions are mediated by binding of the active form of the TH T3 to the specific nuclear receptors TRalpha and TRbeta, which are transcription factors. Using mutant mice lacking TRs or deficient for TH production, we show that T3 influences neonatal erythropoiesis through TRalpha.

Direct repression of prdm1 by Bcl-6 inhibits plasmacytic differentiation.

We have identified two intronic regions of mouse prdm1, the gene encoding B lymphocyte-induced maturation protein-1 (Blimp-1), which confer transcriptional repression in response to Bcl-6. The Bcl-6 response element in intron 5, which is conserved between mice and humans, was studied in detail. It binds Bcl-6 in vitro and was shown by chromatin immunoprecipitation to be occupied by Bcl-6 in vivo.

Changes in histone acetylation are associated with differences in accessibility of V(H) gene segments to V-DJ recombination during B-cell ontogeny and development.

Although V(D)J recombination is thought to be regulated by changes in the accessibility of chromatin to the recombinase machinery, the mechanisms responsible for establishing "open" chromatin are poorly understood. We performed a detailed study of the acetylation status of histones associated with 11 V(H) gene segments, their flanking regions, and various intergenic elements during B-cell development and ontogeny, when V(D)J recombination is highly regulated. Histone H4 shows higher and more-regulated acetylation than does histone H3 in the V(H) locus.

An interfering form of Blimp-1 increases IgM secreting plasma cells and blocks maturation of peripheral B cells.

B lymphocyte-induced maturation protein-1 (Blimp-1) can drive plasmacytic differentiation in cultured cell models. To determine the role of Blimp-1 in B cell development in vivo, we have generated transgenic mice expressing an interfering truncated form of Blimp-1 (TBlimp) under the control of an immunoglobulin heavy chain promoter and intronic (E) enhancer. TBlimp-transgenic mice have elevated serum IgM and a prolonged IgM response.