Interaction of pathogens with cells of the immune system results in activation of inflammatory gene expression. This response, while vital for immune defence, is frequently deleterious to the host due to the exaggerated production of inflammatory proteins. The scope of inflammatory responses reflects the activation state of signalling proteins upstream of inflammatory genes as well as signal-induced assembly of nuclear chromatin complexes that support mRNA expression1–4. Recognition of post-translationally modified histones by nuclear proteins that initiate mRNA transcription and support mRNA elongation is a critical step in the regulation of gene expression5–10. Here we present a novel pharmacological approach that targets inflammatory gene expression by interfering with the recognition of acetylated histones by the Bromodomain and Extra Terminal domain (BET) family of proteins. We describe a synthetic compound (I-BET) that by “mimicking” acetylated histones disrupts chromatin complexes responsible for the expression of key inflammatory genes in activated macrophages and confers protection against LPS-induced endotoxic shock and bacteria-induced sepsis. Our findings suggest that synthetic compounds specifically targeting proteins that recognize post-translationally modified histones can serve as a new generation of immunomodulatory drugs.

Germ cell fate in mice is induced in pluripotent epiblast cells in response to signals from extraembryonic tissues. The specification of approximately 40 founder primordial germ cells and their segregation from somatic neighbours are important events in early development. We have proposed that a critical event during this specification includes repression of a somatic programme that is adopted by neighbouring cells. Here we show that Blimp1 (also known as Prdm1), a known transcriptional repressor, has a critical role in the foundation of the mouse germ cell lineage, as its disruption causes a block early in the process of primordial germ cell formation. Blimp1-deficient mutant embryos form a tight cluster of about 20 primordial germ cell-like cells, which fail to show the characteristic migration, proliferation and consistent repression of homeobox genes that normally accompany specification of primordial germ cells. Furthermore, our genetic lineage-tracing experiments indicate that the Blimp1-positive cells originating from the proximal posterior epiblast cells are indeed the lineage-restricted primordial germ cell precursors.

SUMMARY Although in vitro studies of embryonic stem cells have identified polycomb repressor complexes (PRCs) as key regulators of differentiation, it remains unclear as to how PRC-mediated mechanisms control fates of multipotent progenitors in developing tissues. Here, we show that an essential PRC component, Ezh2, is expressed in epidermal progenitors but diminishes concomitant with embryonic differentiation and with postnatal decline in proliferative activity. We show that Ezh2 controls proliferative potential of basal progenitors by repressing the Ink4A-Ink4B locus and tempers the developmental rate of differentiation by preventing premature recruitment of AP1 transcriptional activator to the structural genes that are required for epidermal differentiation. Together, our studies reveal that PRCs control epigenetic modifications temporally and spatially in tissue-restricted stem cells. They maintain their proliferative potential and globally repressing undesirable differentiation programs while selectively establishing a specific terminal differentiation program in a stepwise fashion.

MicroRNAs (miRNAs) have important roles in diverse cellular processes, but little is known about their identity and functions during early mammalian development. Here, we show the effects of the loss of maternal inheritance of miRNAs following specific deletion of Dicer from growing oocytes. The mutant mature oocytes were almost entirely depleted of all miRNAs, and they failed to progress through the first cell division, probably because of disorganized spindle formation. By comparing single-cell cDNA microarray profiles of control and mutant oocytes, our data are compatible with the notion that a large proportion of the maternal genes are directly or indirectly under the control of miRNAs, which demonstrates that the maternal miRNAs are essential for the earliest stages of mouse embryonic development.Supplemental material is available at http://www.genesdev.org.Received November 20, 2006; revised version accepted January 29, 2007. MicroRNAs (miRNAs) are a large family of short noncoding RNAs (17-25 nucleotides) (He and Hannon 2004). A key function of miRNAs is to repress expression of their target genes through sequence complementation, which reduces the abundance of the target mRNAs and/ or inhibits their translation (Bartel 2004;Bagga et al. 2005). MiRNA genes are first transcribed into miRNA primary transcripts by RNA polymerase II (Kim 2005). These primary transcripts are then processed into miRNA precursors by the Drosha/DGCR8 complex and transported from the nucleus to the cytoplasm. Finally, Dicer processes the miRNA precursors into mature miRNAs. From previous studies, Dicer seems to be critical for early mouse development since its loss of function is embryonic lethal at embryonic day 7.5 (E7.5) (Bernstein et al. 2003).In this study, we have examined the role of miRNAs in the mouse oocyte. The mature oocyte contains a number of molecules that are manufactured during oocyte maturation and utilized during early stages of development before activation of the embryonic genome (Dean 2002). It is likely that miRNAs would also be present in the oocyte, but no information is yet available in the mouse. The purpose of this study was to determine if there is significant inheritance of maternal miRNAs in mammalian zygotes, and to investigate if they play a critical role in early mammalian development. We have investigated how the loss of Dicer affects synthesis of miRNA during oocyte maturation and their impact on mRNA and early development. Results and DiscussionFirst, we decided to investigate if there is significant biogenesis of miRNAs in developing oocytes, and their inheritance in the zygote. We therefore examined expression of miRNAs in single cells during oogenesis by a real-time PCR-based miRNA expression profiling method that we recently developed (C. Tang et al. 2006a,b). We compared the miRNA expression profiles of growing oocytes obtained from females 15-16 d after birth (postnatal days 15-16 [P15-P16]) and at P20-P21, and of mature oocytes from adult females. This analysis reveled dynamic chan...

The Src family of protein tyrosine kinases (Src-PTKs) is important in the regulation of growth and differentiation of eukaryotic cells. The activity of Src-PTKs in cells of different types is negatively controlled by Csk, which specifically phosphorylates a conserved regulatory tyrosine residue at the carboxy-terminal tail of the Src-PTKs. Csk is mainly cytoplasmic and Src-PTKs are predominantly membrane-associated. This raises a question about the mechanism of interaction between these enzymes. Here we present Cbp--a transmembrane phosphoprotein that is ubiquitously expressed and binds specifically to the SH2 domain of Csk. Cbp is involved in the membrane localization of Csk and in the Csk-mediated inhibition of c-Src. In the plasma membrane Cbp is exclusively localized in the GM1 ganglioside-enriched detergent-insoluble membrane domain, which is important in receptor-mediated signalling. These findings reveal Cbp as a new component of the regulatory mechanism controlling the activity of membrane-associated Src-PTKs.