Emerging concepts suggest that macrophage functional phenotype is regulated by transcription factors that define alternative activation states. We found that RBP-J, the major nuclear transducer of Notch signaling, augmented TLR4-induced expression of key mediators of classically activated M1 macrophages and thus innate immune responses to L. monocytogenes. Notch-RBP-J signaling controlled expression of the transcription factor IRF8 that induced downstream M1-specific genes. RBP-J promoted IRF8 protein synthesis by selectively augmenting IRAK2-dependent TLR4 signaling to the MNK1 kinase and downstream translation initiation control through eIF4E. These results define a signaling network in which Notch-RBP-J and TLR signaling are integrated at the level of IRF8 protein synthesis and identify a mechanism by which heterologous signaling pathways can regulate TLR-induced inflammatory macrophage polarization.

Gain-of-function mutations in exon 3 of beta-catenin (CTNNB1) are specific for Wilms' tumors that have lost WT1, but 50% of WT1-mutant cases lack such "hot spot" mutations. To ask whether stabilization of beta-catenin might be essential after WT1 loss, and to identify downstream target genes, we compared expression profiles in WT1-mutant versus WT1 wild-type Wilms' tumors. Supervised and nonsupervised hierarchical clustering of the expression data separated these two classes of Wilms' tumor. The WT1-mutant tumors overexpressed genes encoding myogenic and other transcription factors (MOX2, LBX1, SIM2), signaling molecules (TGFB2, FST, BMP2A), extracellular Wnt inhibitors (WIF1, SFRP4), and known beta-catenin/TCF targets (FST, CSPG2, CMYC). Beta-Catenin/TCF target genes were overexpressed in the WT1-mutant tumors even in the absence of CTNNB1 exon 3 mutations, and complete sequencing revealed gain-of-function mutations elsewhere in the CTNNB1 gene in some of these tumors, increasing the overall mutation frequency to 75%. Lastly, we identified and validated a novel direct beta-catenin target gene, GAD1, among the WT1-mutant signature genes. These data highlight two molecular classes of Wilms' tumor, and indicate strong selection for stabilization of beta-catenin in the WT1-mutant class. Beta-Catenin stabilization can initiate tumorigenesis in other systems, and this mechanism is likely critical in tumor formation after loss of WT1.

Methamphetamine (METH) is an illicit and potent psychostimulant, which acts as an indirect dopamine agonist. In the striatum, METH has been shown to cause long lasting neurotoxic damage to dopaminergic nerve terminals and recently, the degeneration and death of striatal cells. The present study was undertaken to identify the type of striatal neurons that undergo apoptosis after METH. Male mice received a single high dose of METH (30 mg/kg, i.p.) and were killed 24 h later. To demonstrate that METH induces apoptosis in neurons, we combined terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) staining with immunohistofluorescence for the neuronal marker neuron-specific nuclear protein (NeuN). Staining for TUNEL and NeuN was colocalized throughout the striatum. METH induces apoptosis in approximately 25% of striatal neurons. Cell counts of TUNEL-positive neurons in the dorsomedial, ventromedial, dorsolateral and ventrolateral quadrants of the striatum did not reveal anatomical preference. The type of striatal neuron undergoing cell death was determined by combining TUNEL with immunohistofluorescence for selective markers of striatal neurons: dopamine-and cAMP-regulated phosphoprotein, of apparent M r 32,000, parvalbumin, choline acetyltransferase and somatostatin (SST). METH induces apoptosis in approximately 21% of dopamine-and cAMP-regulated phosphoprotein, of apparent M r 32,000-positive neurons (projection neurons), 45% of GABA-parvalbumin-positive neurons in the dorsal striatum, and 29% of cholinergic neurons in the dorsal-medial striatum. In contrast, the SST-positive interneurons were refractory to METH-induced apoptosis. Finally, the amount of cell loss determined with Nissl staining correlated with the amount of TUNEL staining in the striatum of METH-treated animals. In conclusion, some of the striatal projection neurons and the GABAparvalbumin and cholinergic interneurons were removed by apoptosis in the aftermath of METH. This imbalance in the populations of striatal neurons may lead to functional abnormalities in the output and processing of neural information in this part of the brain. Keywords methamphetamine; apoptosis; striatum; projection neurons; interneurons Methamphetamine (METH) is a potent and addictive psychostimulant. The neurotoxic effects of this substituted amphetamine are associated with its ability to induce an overflow of dopamine in the synapse by displacing vesicular dopamine stores (Raiteri et al., 1979; Liang and Rutledge, 1982a,b;Schmidt et al., 1985;Sulzer et al., 1995). Displaced dopamine molecules and its metabolites can be readily oxidized to reactive quinones and semiquinones (Cadet and Brannock, 1998) and nitrogen radicals (Lipton and Rosenberg, 1994;Imam et al., 1999) that affect a wide range of modifications of proteins, sugars, and lipids. Augmented levels of dopamine in the synapse induced by METH have been shown in humans (Wilson et al., 1996;McCann et al., 1998), non-human primates (Seiden et al., 1976;Villemagne et al., 1998;Harvey e...