Expression of c-myb and B-myb oncogenes on myelofibrotic marrow fibroblasts

Dose- and time-dependent expression patterns of zebrafish orthologs of selected E2F target genes in response to serum starvation/replenishment

Targets of E2F transcription factors effectively regulate the cell cycle from worms to humans. Furthermore, the dysregulation of E2F transcription modules plays a highly conserved role in cancers of human and zebrafish. Studying E2F target expression under a given cellular state, such as quiescence, might lead to a better understanding of the conserved patterns of expression in different taxa. In the present study, we used literature searches and phylogeny to identify several targets of E2F transcription factors that are known to be serum-responsive; namely, PCNA, MYBL2, MCM7, TYMS, and CTGF. The transcriptional serum response of zebrafish orthologs of these genes were quantified under different doses (i.e., 0, 0.1, 1, 3, and 10% FBS) and time points (i.e., 6, 24 and 48 hours, h) using quantitative RT-PCR (qRT-PCR) in the zebrafish fibroblast cells (ZF4). Our results indicated that mRNA expression of zebrafish pcna, mybl2, mcm7 and tyms drastically decreased while that of ctgf increased with decreasing serum levels as observed in mammals. These genes responded to serum starvation at 24 and 48 h and to the mitogenic stimuli as early as 6 h except for ctgf whose expression was significantly altered at 24 h. The zebrafish Mcm7 protein levels also were modulated by serum starvation/replenishment. The present study provides a foundation for the comparative analysis of quantitative expression patterns for genes involved in regulation of cell cycle using a zebrafish serum response model.

NF-kappa B as a central mediator in the induction of TGF-beta in monocytes from patients with idiopathic myelofibrosis: an inflammatory response beyond the realm of homeostasis

Immune-mediated mechanisms have been implicated in the etiology of idiopathic bone marrow fibrosis (IMF). However, the mechanism remains poorly defined. Compared with healthy controls, IMF monocytes are overactivated, with increased production of TGF-beta and IL-1. TGF-beta is central to the progression of fibrosis in different organs. In the lung, fibrosis is associated with up-regulation of TGF-beta-inducible genes. Because IL-1 and TGF-beta have pro- and antiinflammatory properties and neither appears to regulate the high levels of each other in IMF, we studied the mechanism of this paradigm. We focused on the role of RelA, a subunit of the transcription factor, NF-kappaB that is associated with inflammatory responses. We transiently knocked out RelA from IMF monocytes with antisense oligonucleotides and showed that RelA is central to IL-1 and TGF-beta production and to the adhesion of IMF monocytes. Because the NF-kappaB family comprises subunits other than RelA, we used aspirin and sodium salicylate to inhibit kinases that activate NF-kappaB and showed effects similar to those of the RelA knockout system. It is unlikely that RelA could be interacting directly with the TGF-beta gene. Therefore, we determined its role in TGF-beta production and showed that exogenous IL-1 could induce TGF-beta and adherence of IMF monocytes despite the depletion of NF-kappaB. The results indicate that IL-1 is necessary for TGF-beta production in IMF monocytes, but NF-kappaB activation is required for the production of endogenous IL-1. Initial adhesion activates NF-kappaB, which led to IL-1 production. Through autocrine means, IL-1 induces TGF-beta production. In total, these reactions maintain overactivation of IMF monocytes.