Transcription factors of the alternative NF-kappa B pathway are required for germinal center B-cell development
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Authors: De Silva, Nilushi S.; Anderson, Michael M.; Carette, Amanda; Silva, Kathryn; Heise, Nicole; Bhagat, Govind; Klein, Ulf
Abstract
The NF-kappa B signaling cascade relays external signals essential for B-cell growth and survival. This cascade is frequently hijacked by cancers that arise from the malignant transformation of germinal center (GC) B cells, underscoring the importance of deciphering the function of NF-kappa B in these cells. The NF-kappa B signaling cascade is comprised of two branches, the canonical and alternative NF-kappa B pathways, mediated by distinct transcription factors. The expression and function of the transcription factors of the alternative pathway, RELB and NF-kappa B2, in late B-cell development is incompletely understood. Using conditional deletion of relb and nfkb2 in GC B cells, we here report that ablation of both RELB and NF-kappa B2, but not of the single transcription factors, resulted in the collapse of established GCs. RELB/ NF-kappa B2 deficiency in GC B cells was associated with impaired cell-cycle entry and reduced expression of the cell-surface receptor inducible T-cell costimulator ligand that promotes optimal interactions between B and T cells. Analysis of human tonsillar tissue revealed that plasma cells and their precursors in the GC expressed high levels of NF-kappa B2 relative to surrounding lymphocytes. Accordingly, deletion of nfkb2 in murine GC B cells resulted in a dramatic reduction of antigen-specific antibody-secreting cells, whereas deletion of relb had no effect. These results demonstrate that the transcription factors of the alternative NF-kappa B pathway control distinct stages of late B-cell development, which may have implications for B-cell malignancies that aberrantly activate this pathway.
Genome-Wide Association Study to Identify Genes Related to Renal Mercury Concentrations in Mice
ENVIRONMENTAL HEALTH PERSPECTIVES
Authors: Alkaissi, Hammoudi; Ekstrand, Jimmy; Jawad, Aksa; Nielsen, Jesper Bo; Havarinasab, Said; Soderkvist, Peter; Hultman, Per
Abstract
BACKGROUND: Following human mercury (Hg) exposure, the metal accumulates in considerable concentrations in kidney, liver, and brain. Although the toxicokinetics of Hg have been studied extensively, factors responsible for interindividual variation in humans are largely unknown. Differences in accumulation of renal Hg between inbred mouse strains suggest a genetic interstrain variation regulating retention or/and excretion of Hg. A. SW, DBA/2 and BALB/C mouse strains accumulate higher amounts of Hg than B10.S. OBJECTIVES: We aimed to find candidate genes associated with regulation of renal Hg concentrations. METHODS: A. SW, B10.S and their F1 and F2 offspring were exposed for 6 weeks to 2.0 mg Hg/L drinking water. Genotyping with microsatellites was conducted on 84 F2 mice for genome-wide scanning with ion pair reverse-phase high-performance liquid chromatography (IP RP HPLC). Quantitative trait loci (QTL) were established. Denaturing HPLC was used to detect single nucleotide polymorphisms for haplotyping and fine mapping in 184 and 32 F2 mice, respectively. Candidate genes (Pprc1, Btrc and Nfkb2) verified by fine mapping and QTL were further investigated by real-time polymerase chain reaction. Genes enhanced by Pprc1 (Nrf1 and Nrf2) were included for gene expression analysis. RESULTS: Renal Hg concentrations differed significantly between A. SW and B10. S mice and between males and females within each strain. QTL analysis showed a peak logarithm of odds ratio score 5.78 on chromosome 19 (p = 0.002). Haplotype and fine mapping associated the Hg accumulation with Pprc1, which encodes PGC-1-related coactivator (PRC), a coactivator for proteins involved in detoxification. Pprc1 and two genes coactivated by Pprc1 (Nrf1 and Nrf2) had significantly lower gene expression in the A. SW strain than in the B10. S strain. CONCLUSIONS: This study supports Pprc1 as a key regulator for renal Hg excretion.